Running head: HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

Lexical Processes in the Recognition of Japanese Horizontal and Vertical Compounds

Koji Miwa
Seminar für Sprachwissenschaft
Eberhard Karls Universität Tübingen, Germany

Ton Dijkstra
Donders Institute for Brain, Cognition, and Behaviour
Radboud University Nijmegen

Address for the correspondence:
Koji Miwa
Seminar für Sprachwissenschaft
Wilhelmstraße 19, Raum 3.22, Eberhard Karls Universität Tübingen
72074 Tübingen, Germany
E-mail: kojimiwa4@gmail.com
Phone: +49 7071 29-73952

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

2

Abstract
This lexical decision eye-tracking study investigated whether horizontal and vertical readings
elicit comparable behavioral patterns and whether reading directions modulate lexical
processes. Response times and eye movements were recorded during a lexical decision taskwith Japanese bimorphemic compound words presented vertically. The data were thenanalyzed together with those obtained in a horizontal lexical decision experiment of Miwa,
Libben, Dijkstra, and Baayen (2014). Linear mixed-effects analyses of response times andeye movements revealed that, although response times and first fixation durations were
notably shorter in horizontal reading than vertical reading, the vertical reading elicited fewer
fixations. Furthermore, while compounds were recognized largely in comparable ways
regardless of reading direction, several lexical processes were found to bereading-direction-dependent. Particularly, processing of the first morpheme was modulated
by reading direction in a late time frame, such that a horizontal reading advantage wasobserved for words with a high frequency first morpheme. All in all, the two reading
directions do not only differ quantitatively in processing speed, but also qualitatively in termsof underlying processing mechanisms.
Keywords: visual word recognition, reading direction, morphological processing,Japanese, lexical decision, eye-tracking

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

3

Lexical Processes in the Recognition of Japanese Horizontal and Vertical Compounds

Horizontal vs. Vertical Readings
In a Google query as of March 9, 2016, the phrase “reading left to right” resulted in
98,800 document counts while the phrase “reading top to bottom” resulted in mere 8,090
counts. This is no surprise. Reading is generally considered to be done horizontally. In thefield of vision research, however, differences between horizontal and vertical readings havebeen studied since the 19th century. In several experiments conducted by Huey (1898),
participants read English texts both silently and aloud in both horizontal and verticalalignments. A processing advantage was witnessed for horizontal reading. Half a century
later, Tinker (1955) tested an effect of systematic practice in vertical reading. Althoughvertical reading was 50% slower than horizontal reading before the practice, thisdisadvantage was minimized to 21.8% after the practice. More recently, Yu, Park, Gerold,and Legge (2010) confirmed that, using alphabetic letter stimuli, vertical reading is slower
than horizontal reading and that the processing cost arises due to a perceptual factor (i.e., asmaller visual-span size in vertical reading) rather than an experiential factor (i.e.,
oculomotor training).
While alphabetic languages are predominantly written horizontally, except in special
contexts (e.g., road signs and book titles), Japanese texts are written both horizontally andvertically, depending on genres. While online texts and technical articles are writtenhorizontally, novels (Figure 1a) and newspapers are written vertically. Moreover, Japanesereaders grow up in an environment full of horizontal and vertical words (Figure 1b). Because
both horizontal and vertical alignments are ubiquitous in Japanese, this language provides afair testing ground to investigate potential effects of reading directions. In past studies on theHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

4effects of reading direction in Japanese, Osaka (1989) reported that saccade length was 5.8
characters on average in horizontal reading while Osaka and Oda (1991) reported that
average saccade length in vertical reading was 5.5 characters. The authors concluded thatthese figures were comparable. Note, however, that there was no direct statistical comparison.
More recently, Igawa, Nakayama, Maeda, and Tabuchi (2006) compared horizontal andvertical text readings in Japanese, using eye-tracking. They reported that vertical reading
elicited more fixations, slower saccade velocity, and higher subjective difficulty in reading.
Apparently, the accumulated knowledge indicates that horizontal reading is, albeit to varying
degrees, always faster and less costly than vertical reading.

Morphological Processes
When readers perceive a compound word, such as blackboard consisting of themorphemes black and board, there are three possible ways to recognize it: the morphologicalparts are processed before the whole (sublexical view: e.g., Taft & Forster, 1975), the wholeis processed before the parts (supralexical view: e.g., Giraudo & Grainger, 2001), or the twoprocesses proceed in parallel (dual-route view: e.g., Baayen, Dijkstra, & Schreuder, 1997). If
one attempts to construct a language-general model of morphological processing, however,linguistic variations should be taken into account. In Japanese and Chinese, each orthographic
symbol (hereafter character) represents a morpheme (e.g.,‘gun’) and is therefore

considered to be a morphogram (Rogers, 2005). Although morphemes are typically defined asminimal meaningful units, this is not a language-general definition because morphograms inthese languages contain a semantic radical, which often represents a general meaning of themorphograms (e.g.,‘rifle’,‘bronze, and‘bell’ all share the semantic radical ‘steel’ and belong to the same semantic category), as shown in Figure 1c. An issue is how
these hierarchically structured morphological units contribute during recognition of

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

morphographic compound words (e.g.,5‘hunting rifle’). Although evidence has been

accumulated that all of these morphological components contribute to compound recognition(Miwa, Libben, Dijkstra, & Baayen, 2014; Taft, Zhu, & Peng, 1999), the order ofmorphological processing is still under debate. Taft et al. (1999) proposed that compound
recognition starts from radicals while Miwa et al. (2014) proposed that character units leadthe recognition process.
In morphological research, cross-language orthographic variations have four
important consequences for processing. First, because characters represent a morpheme,
rather than a phoneme, morphographic compounds are typically shorter in length thanalphabetic compounds, making supralexical processing more likely. Second, a morphologicalboundary becomes perceptually obvious in Japanese, which may motivate bottom-up
processing from morphemes. Third, compounds with the same number of morphemes always
fit into the same rectangle space, which makes sequential left-to-right processing lessobligatory (i.e., the head morpheme can be identified without sequential scanning). Fourth,because all morphograms contain a smaller meaningful unit, morphemes may or may not be
the minimal meaningful processing unit (Miwa et al., 2014; Taft et al., 1999 respectively).
Orthography is therefore not a negligible factor if one attempts to understandlanguage-general morphological processing.

< Insert Figure 1 around here >The Present Research
Up until now, studies on horizontal vs. vertical reading and on lexical processes havedeveloped as distinct streams of research. In this study, as shown in Figure 1 (c), we linked
these issues and investigated how different the two reading directions are and whether theHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

6

two reading directions affect lexical processes differentially. If we assume that lexical effects(e.g., compound frequency effects) reflect language-general central processes, the effects
should be observed regardless of task variations. The present eye-tracking lexical decision
study with Japanese bimorphemic compound words examined the following issues.
First, we studied the longstanding issue in vision research: whether there is an overall
processing cost for one alignment over the other. This was investigated with Japanese
two-character kanji words. Among the three orthographic scripts used in Japanese (i.e., kanji,hiragana, katakana), kanji is used to represent lexical categories and tend to receive more eye
fixations (Kajii, Nazir, & Osaka, 2001). Furthermore, in the BCCWJ word list (National
Institute for Japanese Language and Linguistics, 2013), we found that 60% of the kanji words
consist of two-characters.
Use of Japanese isolated words for testing reading direction effects is new andeffective (for use of isolated words in English, see Yu et al., 2010). Given the prevalence of
online texts, which are almost always presented horizontally, we expect some processing costfor vertical reading even in a context of isolated word lexical decision. If the processing costin vertical reading is perceptual in nature (Yu et al., 2010), a main effect of reading direction
should be observed at the earliest fixation. This method is also important for the purpose ofunderstanding word recognition in general and eye movements in a lexical decision task inparticular; only response times have received researchers’ attention for this most popularpsycholinguistic task (Libben & Jarema, 2002), although there are usually multiple eye
fixations when words are perceived in isolation (Hyönä, Laine, & Niemi, 1995; Kuperman,
Schreuder, Bertram, & Baayen, 2009; Miwa et al., 2014).
Second, we studied whether reading directions modulate lexical processes. Dependingon the assumption of attentional units, vertical reading may or may not be different fromhorizontal reading. If attention is directed to small orthographic units, reading direction has a

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

7

drastic consequence on lexical processes, because their relative order changes. Inhoff,
Pollatsek, Posner, and Rayner (1989) suggested that, in English, attention does not shift on aletter-by-letter basis. For Japanese word reading, Miwa et al.’s (2014) character-driven model
similarly predicts that attention does not shift on a radical-by-radical basis. They studied eye
fixation durations recorded during lexical decision experiments for horizontally presented
Japanese compounds and proposed that morphological processing in Japanese is initiallyguided by characters, rather than radicals or the whole word unit.
However, it is not yet guaranteed that character-driven processing is the rule invariant
across all task conditions. Vertical reading may motivate more analytic processing if readers
have more experiential or perceptual constraints in this alignment. Bertram and Hyönä’s(2003) visual acuity hypothesis holds that longer words are more likely to be processed fromparts. Given the visual acuity constraint in vertical reading (Yu et al., 2010), it is possible thatmorphological components (i.e., radical and characters) contribute more to lexical processing
in a vertical alignment. The lateralized word recognition model of Lavidor, Babkoff, andFaust (2001), which claims that words presented in a non-standard visual format are notprocessed holistically in the left hemisphere, also supports this prediction, because verticalreading is familiarity-wise less standard than horizontal reading even in Japanese.
Alternatively, vertical reading might motivate holistic processing if verticallypresented words are perceived in a qualitatively different manner due to a lack of horizontal
eye movements. Furthermore, if expertise in morphographic word recognition is marked byleft-side bias, as proposed by Hsiao and Cottrell (2009), vertical alignment may facilitate yet
another kind of holistic processing, because a left-side-bias motivates attention to a bit of
information from the first and second characters simultaneously (e.g.,‘animal’ and ‘steel’ in the example shown in Figure 1). Such qualitative differences between the twoalignments were already speculated to exist by Huey (1898): “it is probable that the subject

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

8

may have a greatest possible speed by one method and a greatest normal speed or speed of
comfortable and intelligent reading by quite another” (p. 579).
Using Eye-Tracking to Study Morphological Processing
In this study, we investigated this horizontal vs. vertical issue from a
psycholinguistic perspective in an experiment combining lexical decision and eye-tracking.
Because participants often make multiple fixations in an isolated word recognition task, thistechnique allows us to tap into the time course of word recognition (Hyöna et al., 1995;
Kuperman et al., 2009; Miwa et al., 2014). The following sections describe the lexical
predictors considered in this study, and our predictions regarding their contribution.
Variables Considered in This Study
Table 1 summarizes descriptive statistics for the linguistic and non-linguistic
predictors considered in this study.
WholeWordFrequency is a log-transformed compound frequency count collected fromthe Balanced Corpus of Contemporary Written Japanese (BCCWJ, Maekawa et al., 2014).
Because this balanced corpus includes lexical statistics in 11 different genres (e.g., blogs,
newspapers, and novels), WholeWordFrequency is relatively reading-direction-independent.
Previous eye-tracking lexical decision studies (Kuperman et al., 2009; Miwa et al., 2014)
reported a small yet significant whole word frequency effect already at the first fixation, notto mention its greater contribution at a later fixation. However, it is not clear whether theeffect is perceptual or lexical in nature. If the word frequency effect is largely due toperceptual familiarity, the effect may be modulated by reading directions, with a larger
magnitude of the effect for vertical reading. This logic is based on previous reports that theword frequency effect is larger for non-native speakers than for native speakers (Gollan,
Montoya, Cera, & Sandoval, 2008).

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

9

To gauge lexical activation at the character and radical levels, character token
frequencies (First/SecondCharacterFrequency) were obtained from the BCCWJ corpus, andradical type frequencies (First/SecondCharacterRadicalCombinability), indicating how many
characters share a given radical, were obtained from Tamaoka and Makioka’s (2004) lexical
database. Morphographic word recognition speed is known to be co-determined by character
frequency (Miwa et al., 2014; Tamaoka & Hatsuzuka, 1998) and radical combinability(Feldman & Siok, 1997; Miwa, Libben, & Baayen, 2012; Taft & Zhu, 1997).
Visual complexity of words was also taken into consideration by means of characterstroke counts (e.g.,‘year’ is written with 6 strokes). It has been reported that visualcomplexity gauged by stroke counts co-determines word recognition processes (Tamaoka &Kiyama, 2013; Tamaoka & Takahashi, 1999). We considered stroke counts for the left andright characters separately (First/SecondCharacterStrokes), because visual complexities ofindividual characters are known to contribute in an asymmetrical manner, depending on thelocation of the eye. Miwa et al. (2014) reported that, although stroke count effects are
inhibitory in a fixated region, they are facilitatory in a to-be-fixated region. A question yet to
be clarified is whether the same decoding mechanism operates also in vertical reading.

< Insert Table 1 around here >A Vertical Lexical Decision with Eye-Tracking Experiment

We conducted a lexical decision experiment in which Japanese compound words were
presented vertically. The obtained data were then combined with those obtained in ahorizontal reading experiment of Miwa et al. (2014). The two levels of Horizontal andHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

10

Vertical of the factor ReadingDirection denoted the former and the latter data sets
respectively.

MethodParticipants. Twenty native Japanese readers (16 females, median age = 22 years old,interquartile range = 3.75) participated at the University of Alberta, Canada. At the time ofthe experiment, the majority of the participants had stayed in Canada for less than half a year
(median = 4.5 months, IQR = 14 months). For the one-month period preceding theexperiment, only a few participants had been exposed to vertical texts more than horizontal
texts (median = 10% of the time, IQR = 22.5%). These statistics provides an idea about how
prevalent horizontal and vertical texts are, although it is difficult to estimate how often texts
are presented in each direction, because reading direction is largely genre-dependent.
In the analyses that follow, the data from the above 20 participants, who readvertically presented words, were compared to those of the 21 participants tested in Miwa et al.
(2014), who read horizontally presented words. There was no significant difference between
the two groups of participants in terms of their age and length of stay in Canada. To further
safeguard against potential effects of individual differences on lexical processes, thelog-transformed participants’ length of stay in Canada (LengthOfStayCanada) was includedin the regression analyses. Because LengthOfStayCanada correlated with log-transformed ageof the participants (r = .59, p < .0001), only the former was considered as a measure ofindividual differences. Idiosyncratic individual variations were accounted for by means ofrandom-intercepts for participants and by-participant random slopes in mixed-effects models.
Materials. The 200 Japanese test words from Experiment 2 of the Miwa et al. (2014)
study were used. These are two-character words sampled pseudo-randomly from a large
lexical database of Amano and Kondo (2003) so that the words covered the entire frequency

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

11

range (see Miwa et al., 2014, for more details on the stimulus selection procedure). This
sampling procedure minimized researchers’ degree of freedom and avoided unnatural sample
distributions (see Forster, 2000, for experimenter bias associated with construction of items).
As nonword stimuli, the 200 nonwords of Miwa et al. (2014) were used here as well. These
were created by changing either the left or right character of an existing word to a
non-character. This was done by replacing a sub-character component with another existing
component.
Apparatus. The lexical decision experiment was designed and controlled byExperiment Builder (SR Research). During the experiment, movements of participants’ righteye were recorded by an Eyelink II head-mounted eye-tracker (SR Research) with a sampling
rate of 250 Hz in the pupil-only mode.
Procedure. In each trial, participants were asked to make a two-choice decision
regarding whether a presented word was an existing Japanese word or a nonword, by pressing
an appropriate button on a Microsoft Sidewinder game pad. A fixation point was always
presented first at the location corresponding to the centre of the first character. It also served
as a drift correction point, i.e., a target word was not presented until participants fixated on
the fixation point. Words were presented in 40-size white font on a black background; thevisual angle for each character was approximately 1.64º. This procedure was identical to thatin Experiment 2 of Miwa et al. (2014) study, except that words were presented vertically, as
shown in Figure 1 (c).

Results and Discussion
Similarities and differences between horizontal and vertical readings. Throughout
this paper, R version 3.2.2 (R Development Core Team, 2015) was used for statisticalanalyses. We initially observed similarities and differences between horizontal and vertical

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

12

reading in general. The panels (a) to (e) in Figure 2 show item-wise correlation between
horizontal and vertical readings for response time, first fixation duration, second fixation
duration, fixation count, and average saccade velocity respectively (with the ggplot2
package, Wickham, 2009). The black dots represent individual words, and the solid lines area linear smooth with a 95% confidence interval. The dotted lines show hypothetical patterns
in which horizontal and vertical readings show identical response and eye movement
behaviours.
Response time and eye movement measures were transformed based on visualinspection of Q-Q normality plots and a Box-Cox transformation with the MASS package(Box & Cox, 1964; Venables & Ripley, 2002). An inverse transformation was applied to RTs(-1000/RT); an inverse square-root transformation was applied to first fixation durations(-100/√first fixation duration); a square-root transformation was applied to second fixations(√second fixation duration). The plotting was done for correctly responded trials after data
trimming (see below for data trimming procedures).
Horizontal and vertical readings can be studied in terms of similarities and differences.
First, it is possible to state that horizontal and vertical lexical decision tasks are similar. In all
panels, except Panel (e), horizontal and vertical readings show a significant correlation,
implying that different reading directions do not alter the underlying cognitive processes
drastically and that certain mechanisms are shared between them. Second, some differences
between the two reading directions can also be observed. With respect to response times(Panel a), the most data points are located above the hypothetical dotted line, meaning that
responses were slower in vertical reading. The observed pattern (the solid line) deviates fromthe expected line particularly for words that elicited faster responses. The same pattern can beseen in Panel (b). These processing costs associated with vertical reading were supported bysignificant effects of ReadingDirection (reference level = Horizontal) as the sole fixed-effectHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

13

in mixed-effects models: β = 0.127, SE = 0.06, p = .042 in a RT analysis, and β = 3.06, SE =0.76, p < .001 in a first fixation duration analysis. In Panel (d), in contrast, more data points
are located below the dotted line, indicating that horizontal reading elicited more fixations. A
mixed-effects analysis again supported this visual inspection (β = -0.08, SE = 0.03, p = .012
for the fixed effect factor ReadingDirection in a trial count analysis). This result is not in linewith Igawa et al’s (2006) report that vertical text reading elicits more eye fixations andimplies that the slower recognition speed in the vertical reading is not due to inflated fixation
counts. An effect of ReadingDirection was not significant in mixed-effects analyses ofsecond fixation durations (Panel c) and saccade velocity (Panel e).
Figure 2 (f) summarizes the approximate time course of horizontal and verticalreadings based on median RTs, median first fixation durations, median second fixation
durations, and mean fixation counts. The figure shows that vertical reading elicited longer
responses and that the cost associated with vertical reading was primarily generated during
the first fixation. The observations of Figure 2 and the mixed-effects modeling with
ReadingDirection as the sole predictor indicate that, even in the context of isolated word
recognition, vertical reading entailed significant processing costs. This is in line withprevious studies on vertical reading. In the following sections, we reevaluate the effects ofReadingDirection with lexical distributional properties as covariates in mixed-effects models
and test whether ReadingDirection modulates any lexical predictors. Reporting effects of aparticular factor both with and without covariates is important, because the two results may
not be identical (see Simmons, Nelson, & Simonsohn, 2011, for their suggestions forpreventing a false-positive report).

< Insert Figure 2 around here >HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

14

Response time analysis. In the sections that follow, (generalized) linear
mixed-effects analyses (Baayen, Davidson, & Bates, 2008) were performed using the lme4
package (Bates, Maechler, & Bolker, 2011) and the languageR package (Baayen, 2008,2011) with p-values computed with Satterthwaite approximations to degrees of freedom withthe lmerTest package (Kuznetsova, Brockhoff, & Christensen, 2015). Because there is an
on-going debate with respect to its appropriate setting (Barr, Levy, Scheepers, & Tily, 2013;
Bates, Kliegl, Vasishth, & Baayen, 2015; Matuschek, Kliegl, Vasishth, Baayen, & Bates,2015), the random-effects structures of the models were set only as complex as was justified
by a likelihood ratio test using a forward-fitting procedure. Fixed-effects were selectedbackward, while consulting p-values (p < .05) and AIC values, from the most complex modelwith all predictors and interactions between ReadingDirection and lexical predictors andTrial. The same approach was taken for all mixed-effects analyses reported below unlessotherwise noted. Centering was done for all the above numerical predictors by subtracting
their mean value from individual values.
The 4,000 data points obtained in this study were combined with the 4,200 data points
obtained in Miwa et al., (2014). RTs shorter than 300 ms and longer than 3000 ms were
excluded (2 data points). After excluding items that elicited a high error rate (> .40) andincorrect responses, 191 words were kept for analyses (7,139 data points).
A linear mixed-effects model was fitted to the inverse transformed RTs (-1000/RT)
initially with all predictors, and potential interactions between ReadingDirection and lexical
predictors were checked. The random-effect structure of the final model includes intercepts
for subjects (SD = 0.18) and items (SD = 0.12), by-subject random slopes for Trial (SD =0.05), WholeWordFrequency (SD = 0.01), SecondCharacterFrequency (SD = 0.01),
FirstCharacterStrokes (SD = 0.003), as well as by-item random contrast for
ReadingDirection (SD = 0.06, indicating greater variance for vertical reading). More complex

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

15

random-effects structures were not justified by a likelihood ratio test. The standard deviationof the residual error was 0.24, and the R-squared calculated for the correlation between thefitted and observed values was .54.
Table 2 summarizes the fixed-effect structure of the final model. Not surprisingly,
there were significant facilitatory contributions of WholeWordFrequency and an experimental
task effect of Trial. Important for the purpose of the present study, there was a main effect ofReadingDirection, indicating that vertically presented words were read more slowly thanhorizontally presented words. ReadingDirection also modulated the effect ofFirstCharacterFrequency (Figure 3a), such that Horizontal advantage was more notable forwords with high FirstCharacterFrequency. The effect of reading direction remained
consistent throughout the experiment (i.e., no ReadingDirection x Trial interaction). In thetheoretical framework of Lavidor et al. (2001), if the standard visual format is determined byan individual's experience with a particular alignment, readers with more experience invertical reading show holistic processing in vertical reading. We considered this possibility
by testing the interaction between WholeWordFrequency and participants’ exposure tovertical reading relative to horizontal reading for the vertical reading data. The prediction was
not statistically supported (p = .342).
Although response speed has been a major dependent variable in word recognition
research, it captures only the end product of processing. A particular lexical effect might
appear and disappear before a response is executed, and the direction of its effect couldchange from inhibition to facilitation as well. For these reasons, the absence of effects forparticular variables in the response time analysis does not imply that these variables are
negligible. In order to tap into the time-course lexical processes themselves, the eye
movement data were analyzed next.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

16< Insert Table 2 and Figure 3 around here >First fixation duration analyses. Overall, the experiment was performed mostly
with two fixations on an item (64% and 58% for horizontal and vertical readings
respectively). Single fixations and three or more fixations were relatively rare (15.2% for one
fixation, 19.1% for three fixations, 3.3% for four fixations, and 0.7% for five fixations). In
order to dissect response times to early and late time frames, only correct trials with exactly
two fixations were analyzed (5,023 data points). We excluded trials with one fixation,
because in these trials the response times are equal to the first fixation durations. In the trials
with exactly two fixations, the first fixation durations are perhaps not contaminated byresponse execution process. The trials excluded in the RT analysis and those with a first
fixation duration shorter than 100 ms were excluded here as well.
In the final model of inverse square-root transformed first fixation durations (4,289
data points), the random-effect structure comprises an intercept for subjects (SD = 0.23) anditems (SD = 0.19) and by-subject random slopes for Trial (SD = 0.05),
FirstCharacterFrequency (SD = 0.03), FirstCharacterStrokes (SD = 0.02), and by-item
random contrasts for ReadingDirection (SD = 0.08). The standard deviation of the residual
error was 0.42, and the R-squared calculated for the correlation between the fitted andobserved values was .49.
The fixed-effects are listed in Table 3. There was a main effect of ReadingDirection,
indicating that advantage of horizontal reading over vertical reading appeared early.
ReadingDirection also modulated Trial (Figure 3b). This indicates that Japanese speakers inthis study benefitted from intensive exposure to vertically aligned words, like the English
speakers tested by Tinker (1955). Perhaps because participants had less exposure to vertical

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

17

reading than horizontal reading in their daily life, the former had more room for performance
improvement.
The lexical effects at the first fixation were more or less comparable to the earlylexical effects reported in Experiment 2 of the Miwa et al. (2014) study, indicating that, atleast with respect to first fixation durations, lexical processing is not affected by changing
reading direction. Regardless of reading direction, there was an early effect ofWholeWordFrequency before the eye scanned the entire word (recall that these are trials with
two fixations), and character frequency contributed more than radical frequency, with only
the former showing a standard facilitatory frequency effect. The asymmetrical contributionsof stroke counts imply a foveal feature decoding cost and a parafoveal magnetic attraction(Hyönä & Bertram, 2004), regardless of reading direction.

< Insert Table 3 around here >Second fixation duration analyses. For the analysis of second fixation durations,the trials excluded in the RT analysis and those with a second fixation duration longer than
800 ms were excluded. In the final model for square-root-transformed second fixations (4,385
data points), the random-effect structure of this model comprises intercepts for subjects (SD =1.16) and items (SD = 0.77). By-subject random slopes for Trial (SD = 0.28), PreviousRT(SD = 0.79), and PreviousFixationDuration (SD = 0.96) were also included. The standard
deviation of the residual error was 2.37, and the R-squared calculated for the correlation
between the fitted and observed values was .54.
The fixed-effects are summarized in Table 4. The main effect of ReadingDirection
was not significant when it was a sole predictor but significant when the covariates were
included. Interestingly, ReadingDirection also interacted with FirstCharacterFrequency,

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

18

such that Horizontal advantage was greater for words with higher FirstCharacterFrequency(Figure 3c). Recall that the interaction involving the same variables was observed in the
response time analysis (Figure 3, Panel a). The super-imposed eye-tracking techniquesuccessfully identified the locus of the FirstCharacterFrequency x ReadingDirection
interaction to be in a late time frame. The facilitatory contribution ofSecondCharacerFrequency and the inhibitory contribution of SecondCharacterStrokes are inline with the shift of attention from the first character (i.e., the initial fixation point location)
to the second character. In this later time frame, WholeWordFrequency facilitates processing
with the largest magnitude of effect among all the lexical predictors.

< Insert Table 4 around here >Fixation count analysis. Fixation counts ranged from 1 to 10 fixations (15.2% for 1
fixation, 61.3% for two fixations, 19.1% for three fixations, 3.3% for four fixations, 0.7% forfive fixations, and 0.3% for six fixations). For the analysis, trials that were excluded in the
RT analysis and those with more than 5 fixations were excluded (13.8% of the data), and7,068 data points remained.
A generalized linear mixed-effects model with a Poisson distribution was fitted to
fixation counts. A final model consisted of the random-effects of participants (SD = 0.07) and
fixed-effects summarized in Table 5. The R-squared calculated for the correlation between
the fitted and observed values was 0.20. It is within our expectation that highly frequentwords and later trials elicited fewer fixations. It is, however, contrary to our expectation thathorizontal reading elicited more fixations than vertical reading. Because participants tested in
the vertical reading task were exposed to horizontal reading 81% of the time and verticalreading 19% of the time on the average, horizontal reading was expected to elicit fewer

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

19

fixations. Yet, this was not the case. ReadingDirection also interacted with
SecondCharacterStrokes; the magnitude of the SecondCharacterStrokes effect was larger invertical reading (Figure 3d).

< Insert Table 5 around here >Saccade velocity analysis. Because saccade velocity was reported to be slower invertical text reading (Igawa et al., 2006), average saccade velocity (visual degrees per
second) was analyzed. For saccade velocity analyses, only initial saccades recorded incorrectly responded trials were considered (6,228 data points). Because exceedingly large
saccades indicate that the eye’s fixation location jumped out of the whole word, which was
not likely in the present lexical decision experiments, data points with a saccade amplitudelarger than 2.5 degrees were excluded. Similarly, because exceptionally short saccades
indicate involuntary microsaccades, data points with a saccade amplitude less than 0.2
degrees were excluded. This cut-off point was based on the conservative idea of
microssacades being 12 arc min (0.2 degrees) because voluntary miniature saccades may
become as short as involuntary microsaccades (Steinman, Haddad, Skavenski, & Wyman,
1973, but see also Martinez-Conde, Otero-Millan, & Macknik, 2014, for a more recently
proposed threshold of 1 degree and a review of microsaccade research). After the above
trimming procedure, 5,896 data points were kept for analyses. Under the general assumptionthat there is no information uptake during saccades, which are fast and ballistic (i.e., thedestination is pre-determined before a saccade is launched), saccade velocity is expected toreflect relatively early processes that were completed before the end of first fixations.
The random-effect structure of the final model comprises intercepts for participants(SD = 7.04) and items (SD = 2.01), and by-subject random slopes for Trial (SD = 1.34),

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

20FirstCharacterFrequency (SD = 0.85), FirstCharacterStrokes (SD = 0.28), andSecondCharacterStrokes (SD = 0.19). By-item random contrasts for ReadingDirection was
also included (SD = 2.62). The standard deviation of the residual error was 9.90, and theR-squared calculated for the correlation between the fitted and observed values was .33.
The fixed effects are summarized in Table 6. Although saccade velocity was slower
in the vertical reading than the horizontal reading, as reported by Igawa et al. (2006), themain effect of ReadingDirection was not significant. However, its interaction with
WholeWordFrequency deserves attention (Figure 3, Panel e), because WholeWordFrequency
is a marker of holistic processing. Apparently, saccades were slower for high frequency
compounds recognized in horizontal reading. Although the interpretation of this interaction is
not straightforward, the effect of the second character complexity (Panel i) can perhaps beinterpreted together. If an upcoming difficulty of processing in a parafoveal region affects
foveal processing like a magnet, as suggested by Hyönä and Bertram (2004), a faster saccade
velocity for low frequency words with a complex second character would not be unexpected.
Saccades were faster also for words with higher FirstCharacterFrequency andSecondCharacterRadicalCombinability.

< Insert Table 6 around here >General Discussion
Vertical vs. Horizontal Readings
The present study compared lexical decision performance with Japanese compounds
in horizontal and vertical alignments. It was found that, in line with past studies, verticallypresented words were read more slowly than horizontally presented words even in the context
of an isolated word recognition task. This was largely because first fixations were notably

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

21

longer in vertical reading, providing support for Yu et al.’s (2010) observation for English
words that relative processing delay in vertical reading is due to visual acuity constraint. This,
however, does not imply that vertical reading is slower and more costly in all measurements.
Interestingly, although eye fixation durations showed a processing advantage for horizontallypresented words, fixation counts showed a processing advantage for vertically presented
words: Vertical reading elicited a significantly smaller number of fixations. Because more
careful processing in the vertical direction reduces the number of fixations, horizontal andvertical readings are considered to differ qualitatively with respect to some underlying
psycholinguistic processes. Possibly, this was instigated by a greater motivation in the reader
to avoid bottom-up regressive saccades in vertical reading. This interpretation is partially
supported by the fact that right-to-left decoding is fully functional (e.g., in Arabic andHebrew), while bottom-to-top decoding is not encouraged in any existing writing systems.
Such variations, however, may be due to historical reasons, anatomical constraints of the eye,or consideration of cognitive efficiency. We leave the empirical comparison of bottom-to-top
and right-to-left saccades to future research.
Note that this vertical reading advantage in fixation counts is not in line with thelarger fixation counts for vertical reading reported by Igawa et al. (2006). A possible sourceof this discrepancy lies in the task demands required in the two experiments (i.e., lexicaldecision in this study and text reading in Igawa et al., 2006). If readers are required to read as
fast as possible, the number of bottom-up saccades might be reduced even in text reading.

Reading Directions and Compound Processing
The present study was the first to test whether different text alignments modulate
lexical effects. This is important for psycholinguistic research, because models of JapaneseHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

22

word recognition must be formulated in such a way that they can account for different textalignments.
First of all, functional overlaps between horizontal and vertical readings deserve
attention, because lexical effects observed to be similar across different reading directions are
considered to be psycholinguistic in nature. Although an early whole word frequency effect
was also reported in the previous lexical decision with eye-tracking studies (Kuperman et al.,2009; Miwa et al., 2014), the present study adds to this finding by demonstrating that thecompound frequency effect was not modulated by reading direction in either response timeand eye fixation analyses. This result shows that an effect of whole word frequency is, rather
than perceptual, largely lexical in nature. Furthermore, in both horizontal and verticalreadings, at least in a foveal region, characters, instead of compounds and radicals, were theprimary processing units, as proposed by Miwa et al. (2014). This indicates that, with respect
to the level of morphological processing, no drastic change (e.g., one route for horizontal
reading and another route for vertical reading) is necessary to account for a general pattern ofcompound processing.
Importantly, however, some lexical effects were modulated by reading direction,
indicating that reading direction has consequences for cognitive processes. Bertram andHyönä’s (2003) visual acuity hypothesis holds that morphological constituents are activatedmore during the processing of long words due to a limitation in visual acuity. Because visualacuity in a vertical direction is more limited than in a horizontal direction (Yu et al., 2010), it
is likely that vertical reading elicits a stronger constituent frequency effect. The firstmorpheme was indeed processed differently in the two reading directions, as gauged by theFirstCharacterFrequency by ReadingDirection interaction. For words with a high frequency
first morpheme, a horizontal reading advantage (or a vertical reading disadvantage) was
observed. If the visual acuity constraint was the source of this interaction, the direction of

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

23

reading would have modulated the lexical effect during an early timeframe. This was,however, not the case. This FirstCharacterFrequency by ReadingDirection interaction wasobserved in RT and second fixation duration analyses, indicating that it is a late effect. One
interpretation is that, just as a modifier constituent is initially analyzed as a head in sentential
reading (Staub, Rayner, Pollatsek, & Hyönä, 2007), the first character of a word was notrecognized as a modifier, or less so, in vertical reading, leading to semantic competition in alate time frame. Importantly, it can be concluded that reading direction has a lasting
consequence on the cognitive operations performed later in processing.
Lavidor et al.’s (2001) lateralized word recognition model holds that only words
presented in a standard visual format are processed holistically. If the definition of standard
visual format is extended to a horizontal alignment, whole compound frequency effects
should be modulated by reading direction, most likely during an early time frame. In ourstudy, this was not the case in response time, eye fixation duration, and fixation countanalyses. However, in the average saccade velocity analysis, a whole word frequency effect
was indeed modulated by reading direction. Therefore, a possibility remains, in line withLavidor et al.’s (2001) view, that certain holistic perceptual or cognitive processes weremodulated by reading direction.
Hsiao and Cottrell (2009) proposed that expert processing is marked by a leftist bias.
If the expert-specific left-side bias arises also in reading vertically presented compoundwords, the left halves of the first and the second character may receive simultaneous attention,
triggering more holistic processing in vertical reading. The present results show, however, nosign of greater holistic processing for vertical reading.

Limitations of the Study and Future Directions

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

24

Possibilities for future study become clear when we consider the methodologicalaspects of the present study with respect to statistical analysis and the experimental paradigm.
Multivariate statistical analyses. As Simmons et al. (2011) suggested, reporting a
result with and without covariates should be encouraged, because the two results may not be
identical. Indeed, in the second fixation analysis of this study, ReadingDirection was
significant only when covariates were included in the model while the ReadingDirection
effect observed at the first fixation was always significant with and without covariates. This
is not surprising, because non-linguistic effects usually account for a large amount ofvariance in psycholinguistic experiments (Baayen, 2008). In the response time analysis, forexample, when we compared our final model and a model without item-related parameters,
the latter linguistically uninformative model could explain as much as 66% of the varianceexplained by our final model.
With respect to predictors in the mixed-effects models, given the size of thematerials, we kept track of effects of only 13 predictors. It is obvious that many otherpotentially influential predictors can be tested (e.g., familiarity, imageability, neighbourdhood
size, semantic transparency, a number of homophones, age of acquisition, vocabulary size).
However, consideration of many variables comes with interpretational and analyticalchallenges associated with multicollinearity (e.g., see Wurm & Fisicaro, 2014, for arguments
against the practice of residualizing). Because we limited the number of variables to consider,there was no need for decorrelation in this study.
Between-participants vs. Within-participants designs. In this study,
ReadingDirection was tested as a between-participants factor, instead of a within-participants
factor. There are pros and cons for both approaches. The former design is susceptible toindividual differences, but the latter design, as used in Igawa et al. (2006), has limitations as
well. When participants are exposed to the two reading directions in a single experiment, theHORIZONTAL AND VERTICAL COMPOUND RECOGNITION

25

difference between the two conditions become highlighted, which may consequently informparticipants of the aim of the study. In this study, across two task conditions, participants
were comparable with respect to their age and length of stay in Canada, and idiosyncratic
individual differences were minimally accounted for by testing random-intercepts andrandom-slopes in the mixed-effects models.
Lexical decision with eye-tracking paradigm. In the present study, overall, we
obtained consistency between eye-tracking and response time analyses, which successfully
allowed us to infer the locus of particular effects. For example, the compound frequency
effect observed in the RT analysis is largely a late effect, while the locus of the first characterstroke effect is early. Although such consistency provides partial support to the mental
chronometry of Donders (1969/1868), it should be noted that end-point responses do notnecessarily reflect all cognitive processes. The second character stroke counts, for example,
co-determined first and second fixation durations but did not affect RTs. The fact that thecontribution of a particular lexical variable is not reflected in a particular dependent measuredoes not imply that the variable has no contribution. We therefore recommend the recordingof multiple measurements.
Conclusion
The present study tested the Japanese language and its script, in which readings inboth horizontal and vertical alignments are ecologically valid. The main take home messages
are that vertical reading is slower than horizontal reading even in the context of isolated word
recognition and that the observed cost was primarily generated during an early time frame, as
reflected in the longer first fixation durations in vertical reading than horizontal reading. It isnotable, however, that vertical reading also showed a processing advantage: There werefewer fixations in vertical reading than in horizontal reading.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION26

The two alignments did not overly change the pattern of morphological processing at
a foveal region; the contributions of character units were higher than those of compound andradical units in an earliest processing stage regardless of reading directions. However, thehorizontal advantage (or vertical disadvantage) was greater for words with a high frequency
first morpheme, particularly during a late time frame. One interpretation is that it was moredifficult to process the first morpheme as a modifier in vertical reading and that the
non-modifier (i.e., head) interpretation had an inhibiting consequence for lexicality judgment.
The trade-off between fixation durations and fixation counts, as well as reading
directions’ modulation of first character frequency and compound frequency effects, provide
support for the 118-year-old prediction of Huey (1898): It is not a matter of one alignment
being superior to the other, but the two types of readings have some slight yet significant
qualitative differences. To fully account for reading across different scripts and reading
directions, models of Japanese word recognition should consider which underlying
mechanisms, central or peripheral, are responsible for these differences.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

27

References

Amano, S., & Kondo, T. (2003). NTT database series: Lexical properties of Japanese, 2ndrelease [CD-ROM]. Tokyo, Japan: Sanseido.
Baayen, R. H. (2008). Analyzing linguistic data: A practical introduction to statistics using R.
New York, NY: Cambridge University Press.
Baayen, R. H. (2013). languageR: Data sets and functions with "Analyzing Linguistic Data:
A practical introduction to statistics". R package version 1.4.1. Retrieved fromhttp://CRAN.R-project.org/package=languageR
Baayen, R. H., Davidson, D. J., & Bates, D. M. (2008). Mixed-effects modeling with crossed
random effects for subjects and items. Journal of Memory and Language, 59, 390-412.
doi:10.1016/j.jml.2007.12.005
Baayen, R. H., Dijkstra, T., & Schreuder, R. (1997). Singulars and plurals in Dutch: Evidence
for a parallel dual-route model. Journal of Memory and Language, 37, 94-117.
doi:10.1006/jmla.1997.2509
Barr, D. J., Levy, R., Scheepers, C., & Tily, H. J. (2013). Random effects structure for
confirmatory hypothesis testing: Keep it maximal. Journal of Memory and Language,68, 255-278. doi:10.1016/j.jml.2012.11.001
Bates, D., Kliegl, R., Vasishth, S., & Baayen, R. H. (2015). Parsimonious mixed models.
Manuscript submitted for publication. Retrieved from http://arxiv.org/abs/1506.04967
Bates, D., Maechler, M., & Bolker, B. (2011). lme4: Linear mixed-effects models using S4classes. R package version 0.999375-42. Retrieved fromhttp://CRAN.R-project.org/package=lme4
Bertram, R., & Hyönä. J. (2003). The length of a complex word modifies the role ofmorphological structure: Evidence from eye movements when reading short and long
Finnish compounds. Journal of Memory and Language, 48, 615-634.
doi:10.1016/S0749-596X(02)00539-9

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

28

Box, G. E. P. & Cox, D. R. (1964). An analysis of transformations (with discussion). Journalof the Royal Statistical Society B, 26, 211–252.
Donders, F. C. (1969). On the speed of mental processes. Acta Psychologica, 30, 412-431(Original work published in 1868). doi:10.1016/0001-6918(69)90065-1
Feldman, L. B., & Siok, W. W. T. (1997). The role of component function in visual
recognition of Chinese characters. Journal of Experimental Psychology: Learning,
Memory, and Cognition, 23, 776-781. doi:10.1037/0278-7393.23.3.776
Forster, K. I. (2000). The potential for experimenter bias effects in word recognition
experiments. Memory & Cognition, 28, 1109-1115. doi:10.3758/BF03211812
Giraudo, H., & Grainger, J. (2001). Priming complex words: Evidence for supralexical
representation of morphology. Psychonomic Bulletin & Review, 8, 127-131.
doi:10.3758/BF03196148
Gollan, T. H., Montoya, R. I., Cera, C., & Sandoval, T. C. (2008). More use almost always
means a smaller frequency effect: Aging, bilingualism, and the weaker links hypothesis.
Journal of Memory & Language, 58, 787-814. doi:10.1016/j.jml.2007.07.001
Hsiao, J. H., & Cottrell, G. W. (2009). Not all visual expertise is holistic, but it may be leftist.
Psychological Science, 20, 455-463. doi:10.1111/j.1467-9280.2009.02315.x
Huey, E. B. (1898). Preliminary experiments in the physiology and psychology of reading.
The American Journal of Psychology, 9, 575-586. doi:10.2307/1412192
Hyönä, J., & Bertram, R. (2004). Do frequency characteristics of nonfixated words influence
the processing of fixated words during reading? European Journal of Cognitive
Psychology, 16, 104-127. doi:10.1080/09541440340000132
Hyöna, J., Laine, M., & Niemi, J. (1995). Effects of a word's morphological complexity onreaders' eye fixation patterns. Studies in Visual Information Processing, 6, 445-452.
doi:10.1016/S0926-907X(05)80037-6
Igawa, M., Nakayama, N., Maeda, F., & Tabuchi, A. (2006). Tategaki yokogaki bunsho ni
okeru dokushoji no gankyuundo no hikaku [Differences in eye movements during
reading vertically and horizontally printed sentences]. Rinsho Ganka, 60, 1251-1255.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

29

Inhoff, A. W., Pollatsek, A., Posner, M. I., & Rayner, K. (1989). Covert attention and eye
movements during reading. The Quarterly Journal of Experimental Psychology Section
A, 41, 63-89. doi:10.1080/14640748908402353
Kajii, N., Nazir, T. A., & Osaka, N. (2001). Eye movement control in reading unspaced text:
the case of the Japanese script. Vision Research, 41, 2503-2510.
doi:10.1016/S0042-6989(01)00132-8
Kuperman, V., Schreuder, R., Bertram, R., & Baayen, R. H. (2009). Reading ofpolymorphemic Dutch compounds: Towards a multiple route model of lexical
processing. Journal of Experimental Psychology: Human Perception and Performance,
35, 876-895. doi:10.1037/a0013484
Kuznetsova, A., Brockhoff, P. B., & Christensen, R. H. B. (2015). lmerTest: Tests in Linear
Mixed Effects Models. R package version 2.0-25. Retrieved fromhttp://CRAN.R-project.org/package=lmerTest
Lavidor, M., Babkoff, H., & Faust, M. (2001). Analysis of standard and non-standard visual
word format in the two hemispheres. Neuropsychologia, 39, 430–439.
doi:10.1016/S0028-3932(00)00125-1
Libben, G. & Jarema, G. (2002). Mental lexicon research in the new millennium. Brain andLanguage, 81, 1-10. doi:10.1006/brln.2002.2654
Maekawa, K., Yamazaki, M., Ogiso, T., Maruyama, T., Ogura, H., Kashino, W., … Den, Y.
(2014). Balanced corpus of contemporary written Japanese. Language Resources &Evaluation, 48, 345-371. doi:10.1007/s10579-013-9261-0
Matuschek, H., Kliegl, R., Vasishth, S., Baayen, H., & Bates, D. (2015). Balancing Type I
Error and Power in Linear Mixed Models. Manuscript submitted for publication.
Retrieved from http://arxiv.org/abs/1511.01864
Martinez-Conde, S., Otero-Millan, J., & Macknik, S. L. (2014). The impact of micro
saccades on vision: towards a unified theory of saccadic function. Nature Reviews
Neuroscience, 14, 83-96. doi:10.1038/nrn3405

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

30

Miwa, K., Libben, G., & Baayen, R. H. (2012). Semantic radicals in Japanese two-character
word recognition. Language and Cognitive Processes, 27, 142-158.
doi:10.1080/01690965.2011.552339
Miwa, K., Libben, G., Dijkstra, T., & Baayen, R. H. (2014). The time-course of lexical
activation in Japanese morphographic word recognition: Evidence for acharacter-driven processing model. Quarterly Journal of Experimental Psychology, 67,
79-113. doi:10.1080/17470218.2013.790910
National Institute for Japanese Language and Linguistics. (2012). Balanced Corpus ofContemporary Written Japanese: Shonagon. Retrieved fromhttp://www.kotonoha.gr.jp/shonagon/
National Institute for Japanese Language and Linguistics. (2013). BCCWJ Word List.
Retrieved from http://pj.ninjal.ac.jp/corpus_center/bccwj/freq-list.html
Osaka, N. (1989). Eye fixation and saccade during kana and kanji text reading: Comparisonof English and Japanese text processing. Bulletin of the Psychonomic Society, 27,
548-550. doi:10.3758/BF03334665
Osaka, N., & Oda, K. (1991). Effective visual field size necessary for vertical reading during
Japanese text processing. Bulletin of Psychonomic Society, 29, 345-347.
doi:10.3758/BF03333939
R Development Core Team (2015). R: A language and environment for statistical computing.
R Foundation for Statistical Computing, Vienna, Austria. Retrieved fromhttp://www.R-project.org.
Rogers, H. (2005). Writing systems: A linguistic approach. Malden, MA: Blackwell
Publishing.
Simmons, J. P., Nelson, L. D., & Simonsohn, U. (2011). False-positive psychology:
Undisclosed flexibility in data collection and analysis allows presenting anything as
significant. Psychological Science, 22, 1359-1366. doi:10.1177/0956797611417632
Staub, A., Rayner, K., Pollatsek, A., & Hyönä, J. (2007). The time course of plausibility
effects on eye movements in reading: Evidence from noun-noun compounds. Journal of

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

31

Experimental Psychology: Learning, Memory, and Cognition, 33, 1162-1169.
doi:10.1037/0278-7393.33.6.1162
Steinman, R. M., Haddad, G. M., Skavenski, A. A., & Wyman, D. (1973). Miniature eye
movement. Science, 181, 810-819. doi:10.1126/science.181.4102.810
Taft, M., & Forster, K. (1975). Lexical storage and retrieval of prefixed words. Journal ofverbal learning and verbal behavior, 14, 638-647.
doi:10.1016/S0022-5371(75)80051-X
Taft, M., & Zhu, X. (1997). Submorphemic processing in reading Chinese. Journal of
Experimental Psychology: Learning Memory, and Cognition, 23, 761-775.
doi:10.1037/0278-7393.23.3.761
Taft, M., Zhu, X., & Peng, D. (1999). Positional specificity of radicals in Chinese character
recognition. Journal of Memory and Language, 40, 498-519.
doi:10.1006/jmla.1998.2625
Tamaoka, K. & Hatsuzuka, M. (1998). The effects of morphological semantics on theprocessing of Japanese two-kanji compound words. Reading and Writing: An
Interdisciplinary Journal, 10, 293-322. doi:10.1007/978-94-015-9161-4_8
Tamaoka, K., & Kiyama, S. (2013). The effects of visual complexity for Japanese kanji
processing with high and low frequencies. Reading and Writing: An Interdisciplinary
Journal, 26, 205-223. doi:10.1007/s11145-012-9363-x
Tamaoka, K., & Takahashi, N. (1999). The effects of word frequency and orthographic
complexity on the writing process of Japanese two-morpheme compound words. The
Japanese Journal of Psychology, 70, 45-50. doi:10.4992/jjpsy.70.45
Tamaoka, K., & Makioka, S. (2004). New figures for a Web-accessible database of the 1,945
basic Japanese kanji, fourth edition. Behavior Research Methods, Instruments, &Computers, 36, 548-558. doi:10.3758/BF03195601
Tinker, M. (1955). Perceptual and oculomotor efficiency in reading materials in vertical andhorizontal arrangements. The American Journal of Psychology, 68, 444-449.
doi:10.2307/1418529

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

32

Venables, W. N. & Ripley, B. D. (2002). Modern applied statistics with S. Fourth edition.
New York: Springer.
Wickham, H. (2009). ggplot2: Elegant graphics for data analysis. New York: Springer.
Wurm, L. H., & Fisicaro, S. A. (2014). What residualizing predictors in regression analyses
does (and what it does not do). Journal of Memory and Language, 72, 37-48.
doi:10.1016/j.jml.2013.12.003
Yu, D. Park, H. Gerold, D., & Legge, G. E. (2010). Comparing reading speed for horizontal
and vertical English text. Journal of Vision, 10, 1-17. doi:10.1167/10.2.21

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

33

Author noteThis research was supported by the Izaak Walton Killam scholarship from the Killam Trusts
to the first author. Response time and eye movement data after data trimming, accompanying
participant and item properties, will be available on the first author’s website(http://www.kojimiwa.com/publication.html). The frequency data collected from theBalanced Corpus of Contemporary Written Japanese (BCCWJ) are published with permissionof the National Institute for Japanese Language and Linguistics. Authors thank Victor
Kuperman and anonymous reviewers for their comments on an earlier version of this paper.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

34

Table 1
Descriptive Statistics for the Predictors Considered in This Study.
Type

Predictor

Range (Mean, SD) / Levels

CompoundWholeWordFrequency (log)

4.6: 11.4 (M = 6.4, SD = 1.4)

Character

FirstCharacterFrequency (log)

4.8: 13.6 (M = 10.6, SD = 1.6)

Character

SecondCharacterFrequency (log)

5.1: 13.6 (M = 11.0, SD = 1.5)

RadicalFirstCharacterRadicalCombinability (log)0.7: 4.7 (M = 3.1, SD = 1.1)

RadicalSecondCharacterRadicalCombinability (log)0.7: 4.7 (M = 3.0, SD = 1.1)

FeatureFirstCharacterStrokes

3: 21 (M = 9.8, SD = 4.1)

FeatureSecondCharacterStrokes

2: 21 (M = 9.6, SD = 3.8)

Task

ReadingDirection

Levels: Horizontal, Vertical

Task

Trial (/100)

0.13: 4.13 (M = 2.1, SD = 1.1)

Task

PreviousRT (-1000/)-3.2: -0.4 (M = -1.6, SD = 0.4)

Task

PreviousTrialCorrect

Levels: Correct, Incorrect

Task

PreviousFixationDuration (-100/ )-15.8: -2.6 (M = -5.2, SD = 0.8)

Individual

LengthOfStayCanada (log)

0: 4.7 (M = 2.0, SD = 1.3)

Note. The superscripts represent the method of data transformation. The mean and range arepresented for the transformed values before a centering procedure.

Running head: HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

Table 2
Fixed-Effects in the Response Time Analysis.
Response timeType

(Intercept)

EstimateSEt-valuep-value-1.7000.040-42.360< .001

PreviousRT

Task

0.000

0.000

10.142< .001

Trial

Task

-0.0640.009-7.338< .001

PreviousTrialCorrect (Incorrect)

Task

0.057

0.010

6.111

< .001

ReadingDirection (Vertical)

Task

0.115

0.056

2.036

.049

WholeWordFrequency

Compound-0.0590.006-8.837< .001FirstCharacterFrequency

Character-0.0120.009-1.541.125

SecondCharacterFrequency

Character-0.0240.007-3.571< .001FirstCharacterStrokes

Feature

0.007

0.002

3.073

.002

ReadingDirection (Vertical) x FirstCharacterFrequency

Task x Character

0.015

0.006

2.674

.008

Note. The partial effects related to reading directions are bolded.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

36

Table 3Fixed-Effects in the First Fixation Duration Analyses.
First fixation duration

Type(Intercept)

EstimateSEt-valuep-value-5.1140.088-60.723< .001

Trial

Task

-0.0090.014-0.913.367

PreviousTrialCorrect (Incorrect)

Task-0.005

0.024

0.215

.830

ReadingDirection (Vertical)

Task

0.249

0.077

3.534

.001

WholeWordFrequency

Compound-0.0280.010-3.404.001

FirstCharacterFrequency

Character-0.091

0.014-6.212< .001

SecondCharacterFrequency

Character

0.031

0.012

2.926

.004

FirstCharacterRadicalCombinability

Radical

0.041

0.013

3.086

.002

FirstCharacterStrokes

Feature

0.047

0.005

8.991

< .001

SecondCharacterStrokes

Feature-0.0270.004-5.833< .001

LengthOfStayCanada

Individual-0.0690.030-2.364.023

ReadingDirection (Vertical) x Trial

Task x Task

-0.0420.020-2.115.041

Note. The partial effects related to reading directions are bolded.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

37

Table 4
Fixed-Effects in the Second Fixation Duration Analyses.
Second fixation duration

Type(Intercept)

EstimateSEt-valuep-value

14.6200.267

55.660< .001

PreviousFixationDuration

Task-3.5550.166-19.693< .001

PreviousRT

Task

0.901

0.173

5.750

< .001

Trial

Task

-0.4000.056-6.615< .001

PreviousTrialCorrect (Incorrect)

Task

0.602

0.133

3.844

< .001

ReadingDirection (Vertical)

Task

1.294

0.375

3.036

.004

WholeWordFrequency

Compound-0.3970.049-7.082< .001FirstCharacterFrequency

Character-0.0490.067-0.154.877

SecondCharacterFrequency

Character-0.3060.058-5.056< .001

SecondCharacterStrokes

Feature

0.036

0.020

2.116

.036

0.169

0.067

3.149

.002

ReadingDirection (Vertical) x FirstCharacterFrequency Task x Character
Note. The partial effects related to reading directions are bolded.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

38

Table 5
Fixed-Effects in the Mixed-Effects Models for Fixation Counts.
Fixation countType(Intercept)

EstimateSEz-valuep-value

0.773

0.020

39.180< .001

PreviousRT

Task

0.127

0.026

4.860

< .001

Trial

Task

-0.0280.007-3.790< .001

ReadingDirection (Vertical)

Task-0.1020.029-3.570< .001WholeWordFrequency

Compound-0.0360.006-6.160< .001

SecondCharacterStrokes

Feature

0.013

0.003

4.120

< .001

ReadingDirection (Vertical) x SecondCharacterStrokes

Task x Feature

0.009

0.004

2.010

.045

Note. The partial effects related to reading directions are bolded.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

39

Table 6
Fixed-Effects in the Mixed-Effects Models for Saccade Velocity.
Average saccade velocity

Type(Intercept)

EstimateSEt-valuep-value

50.2151.555

32.220< .001

Trial

Task

0.243

0.241

1.730

.092

ReadingDirection (Vertical)

Task-2.7622.227-0.982.332

WholeWordFrequency

Compound-0.4010.162-1.876.062

FirstCharacterFrequency

Character

0.475

0.208

2.321

.024

SecondCharacterRadicalCombinability

Radical

0.367

0.150

2.529

.012

FirstCharacterStrokes

Feature

0.021

0.064

0.353

.725

SecondCharacterStrokes

Feature

0.414

0.056

7.139

< .001

ReadingDirection (Vertical) x WholeWordFrequency

Task x Compound

0.549

0.229

2.103

.037

Note. The partial effects related to reading directions are bolded.

Running head: HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

(a)

(c)

Lexical identification system‘hunting rifle’
Compound‘hunt’‘gun’‘animal’‘steel’Character

Radical(b)
FeatureInput

VerticalHorizontal

Figure 1. Horizontal and vertical writing in Japanese (Panels a and b) and ahierarchical morphological structure of bimorphemic compounds in Japanese andtwo reading directions (Panel c).
Note: The dotted arrows indicate the direction of reading. Panel (a) and Panel (b) are
adapted with permission of Aozora in Browsers and Åsa Gilbertson respectively.

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION(a) Response time●●(b) 1st fixation duration

−4.0

●

●

●
●

Vertical

−1.3

−1.5

−1.7

●

●
●

●●

●●
●
●●
●
●●
● ●
●
● ● ●
●
●●●
●●
● ●
●
●● ●
●
●●
●
●
●
●
●
●
●
●●●
●
●
●
●
●
●
●●
● ●
●●●
●
●
●
●● ● ●●
●
●
●●●
● ●
●
● ●
●
●
●●
●●● ● ●
● ●●● ● ●
●●●
●
●●
●
●
●
●
●
●
● ●● ●●● ●●●●●● ●● ●
●
●●●
●●
●
●●●
● ●
●
●
●
● ●
● ● ●● ●●●●●●● ● ●●●● ●● ●●●●●●●● ● ● ● ●●
●
●
●
●
●
● ●
●
● ●●
●
● ●
●
●

−5.5

−1.8

−1.6

−1.4

−1.2

−6.0

Horizontal

−5.5

●
●
●● ●
●
●
● ● ●●●●● ●●● ●●●●● ● ● ●
●●
● ●●
●
●
●
●● ●● ●●
●● ●
●● ●●
●●
●●
●● ●
●
●●●● ● ●●●●● ● ●
●
●
● ●
●
●
●
● ●● ●● ●●●●●● ●●● ● ● ●●●●●
● ●●●● ● ●●●●●●● ● ● ●● ● ●●●●●●●● ● ● ●
●
●
●
● ●
●
●
●
●●
●●
●●
●
●●
●
●●
● ●● ●
●
●
●
●
●
●●
● ●
●
●
●
●

r = .69

Vertical

50

40

●●

●

●

●
●

Horizontal

2.5

●

12.5

15.0

35

40

45

●

r = .17

●

2.0

10.0

Horizontal

●
●
●
● ●
● ●
● ●● ●
●
●
●●●
● ● ●
●●● ●
● ●● ●
●
●
●
●
●
●
●
●
●
●
●
●
●
●● ●
●● ●●● ●●
● ● ●
●
●
●
●
● ●●● ●
●●
●●
●●
●
● ●
●
●●
●
●
●●●
●
●
●
●●
●
●●
●
●●
●●
● ●
● ●
●
●
● ● ●●●●
●
●
●
●
●●
●
● ● ●●● ●● ●●●●● ● ●●●●●●● ●● ●●● ●
●
●
● ●
●
●
●●
●
●
●
●●
●
●● ●
●
●●
●●
●
●●
● ●●●● ●
●
● ●
●
●
●
●
●
●
●
●

50

55

60

Horizontal(f)Figure 2. Scatter plots showing correlations between horizontal and verticalreadings and a graphical summary of the time-course of horizontal and verticalreadings.

●

r = .65●●

Vertical

●

60

● ● ●
●

1.5

12

●
●

●
●

●

(e) Saccade velocity

●

1.5

−4.5

Horizontal(d) Fixation count

2.0

−5.0

●

●

●
●●
●
●
●
●● ●
●
●●
● ● ● ●● ●
● ●●●
● ●
●
●
●
●● ●
●
●
●
●
● ●● ●●
●
●
●
●
●
●
●●
● ● ●
●
●● ●
●● ●●
●●
●
● ●●●
●●
● ●●
●
●
●
●
●
●
●
●
●●●
●
●
●
●●● ●
●● ●●
●
●
●●●●●
● ●
●
●
●●● ●
●
● ●●● ●●●●●● ●
● ●●●●● ●●●●● ●●●● ●● ●●●●
●●●
● ●
●
● ●●
●● ● ●●●●●●● ●● ● ● ●●
●
●
●
●
● ●
●
●
●●
●
●
●

9

−6.0

2.5

15

r = .74

●

−2.0

18

●

−5.0

●
●

●

r = .75

−1.9

●
●

●●

●
● ●

−4.5

Vertical● ●●● ●● ●●●● ●●●● ● ● ●
●
●
●
●
●●
●
● ● ●●●
●
● ●
●
●●● ●
●
● ●●● ●●●
●● ●
●
●
●
●
●
●
●
●
● ●●●● ●●● ●●●●● ●● ● ● ● ● ●● ● ● ●●●● ●●● ● ●●●●● ● ●● ●●●● ●●● ●● ● ●●● ●
●
● ●
●
● ●●●
●● ● ●●
●
●
● ●●
●●
●●● ●
●●
●●
●● ●
● ●●
●●●●
●
● ●
●●
●
●
●
●
● ●●
●●
●
●
●
●
●● ●
●
●●
●
●●
●
●

●

(c) 2nd fixation duration
21●

Vertical

−1.1

41

17.5

20.0

HORIZONTAL AND VERTICAL COMPOUND RECOGNITION

1

−2

−1

0

(d)

(e)

Vertical
−5

0

5

10

SecondCharacterStrokes

2

−3

−1 0

1

2

FirstCharacterFrequency

Horizontal

Vertical

−4

−2

0

2

WholeWordFrequency

Figure 3. Interactions between lexical predictors and reading direction observed in
the mixed-effects model for response times, first fixation durations, second fixation
durations, fixation count, and saccade velocity.
Note: The rugs reflect a distribution of the predictor values.

ReadingDirection

260

Horizontal

ReadingDirection

Horizontal

47 48 49 50 51 52 53

Trial

Saccade Velocity (degrees/sec)

FirstCharacterFrequency

1

220

Horizontal

Vertical

180

ReadingDirection

VerticalSecond Fixation Duration (ms)

420
380

2

ReadingDirection

2.2

−1 0

1.8
1.4

Fixation counts

−3

(c)

340

Horizontal

ReadingDirection

600
560

RT (ms)VerticalFirst Fixation Duration (ms)

(b)

640

(a)

42