Letters read simultaneously 1

Running head: LETTERS READ SIMULTANEOUSLY

Letters in words are read simultaneously,
not in left-to-right sequence.

James S. Adelman and Suzanne J. Marquis
University of Warwick
Maura G. Sabatos-DeVito
University of North Carolina, Chapel Hill

999 words.
Corresponding Author:
James S. Adelman
Department of Psychology,
University of Warwick,
COVENTRY,
CV4 7AL,UK.
Telephone: +44 (0) 24 7615 0233

Electronic mail: J.S.Adelman@warwick.ac.uk

Letters read simultaneously 2
Letters in words are read simultaneously,
not in left-to-right sequence.
The identification of individual letters is necessary for reading words in alphabetic
script (Pelli, Farell, & Moore, 2003). Sequential models of letter processing (Whitney,2001) in reading words posit an initial left-to-right sequence of letter processing (inleft-to-right languages, such as English), each letter taking 10–25 ms to process before thenext is processed. In contrast, simultaneous models of letter processing (e.g., Tydgat &Grainger, 2009) in reading words posit that information about the identity of each letterstarts to be extracted at the same time point, regardless of horizontal position. Here weshow that people reading four-letter words do not extract identity information for any
letter from an 18 ms display of the word, but some information about all four letters isavailable from 24 ms of display. Our results indicate that a left-to-right sequence ofattention across letters is not used in establishing the cognitive representation of words.
Instead, all letters are processed simultaneously.
The sequential nature of alphabetic written language as a representation of speechsounds, and of words, implies that letters could be processed one-by-one in left-to-rightsequence at the earliest stages of letter identification. Several phenomena have beentreated as consequences of this left-to-right sequence of attention in sequential models ofletter processing (Whitney, 2001). One such phenomenon is better identification of lettersto the left of a briefly presented string (Stevens & Grainger, 2003). In priming paradigms,
where a letter string is read quicker when preceded by a briefly presented similar letter
string, similarity to the left is more important (Peressotti & Grainger, 1995; Schoonbaert &Grainger, 2004). (It is conversely sometimes claimed that increases in contextualenchancement caused by previews (Rumelhart & McClelland, 1982) demonstrate
within-letter-level simultaneous processing, but the effect could be attributed insequential models to increased activation at the feature level.) Whitney and Cornelissen

Letters read simultaneously 3(2007) attribute a wide array of effects, including many involving briefly presented,
masked, letter strings, and length effects, to the (obligatory) left-to-right sequential
read-out of letters. The precise intervals between the processing of the individual letters
are taken to be critical for encoding positional information and word identification, andtherefore also critical for explaining effects related to words with transposed letters(wrods). If this account is correct, the lag between processing a letter and its neighbour tothe right is necessary in processing words.
Simultaneous models of letter processing (Rumelhart & McClelland, 1982; Tydgat &Grainger, 2009) attribute phenomena at the letter level — such as left-to-right decreases inaccuracy — to differing levels of signal strength throughout letter processing that arise
from attentional properties of letter detectors. Other effects, such as length, are presumed
not to be perceptual (notwithstanding eye movements), and are attributed to downstream
processes involving the left-to-right application of spelling-sound rules in producing apronunciation (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001), or to articulation itself(Seidenberg & Plaut, 1998). At the initiation of letter-level processing, however,identification of each letter should begin at the same time, although efficiency or attention
could decline towards the right of the word.
We investigated whether differences in letter identification were due to lag for later
letters (per sequential models) or lower efficiency for later letters (per simultaneousmodels).
Method31 staff and 54 students of the University of Warwick, and 13 other respondents tolocal advertisements were tested as part of a larger study. Pro rated, remuneration wasapproximately £4 (ca. US$6). The participants attempted to read briefly presented
four-letter words, and choose it from two options, presented laterally to match theLetters read simultaneously 4response buttons on a button box. 864 trials were presented, of which 384 criticallydiffered in one letter (e.g., sung vs. lung at the left-most position, or fish vs. fist at theright-most). At each of the 4 positions, 12 word pairs were used, at each of 8 durations
from 12–54 ms. A Sony CPD-G200 17” monitor and an NVIDIA GeForce 7025 graphics
card delivered a 6 ms frame rate at resolution 640x480. Given the posited 10–25 ms effect,
this precision suffices. The word was preceded by a hash mask (##########) andfollowed by a 6 ms blank and the mask again to terminate visual processing (Figure 1a)1 .
Every 108 trials, accuracy feedback and a break were given.
Results and Discussion
Accuracy increased with display duration, and the critical duration of display was
found to be 18–24 ms. After displays of only 18 ms, people performed at chance,
regardless of the position of the required information (from left to right, single-sample
tests against chance, tsubjects (97) = −0.60, 0.75, −0.12, 1.31, p = .547, .454, .907, .194;
titems (23) = −0.29, 0.64, 0.28, 1.28, p = .773, .528, .786, .213). With just 6 ms more display,that is, displays of 24 ms, people performed better than chance, regardless of whether
information was required from the left or the right of the word
(tsubjects (97) = 6.47, 6.93, 6.45, 3.42; titems (23) = 7.09, 7.13, 5.02, 2.95, all p < .001)2 . The
data and a linear mixed effects (LME) analysis are presented in Figure 1b.
The initiation of letter identification therefore occurred for all letters at the sametime point, namely when lower level information arrived from the 18th–24th ms of thestimulus display. The slight horizontal decrease in accuracy observed here (LME lineartrend, z = 2.29, p = .022) at 24 ms, and in previous studies (Stevens & Grainger, 2003;
Tydgat & Grainger, 2009), must therefore be due to differences in the efficiency ofinformation extraction at the different positions.
Overall, these data rule out a sweep of attention sequentially from left-to-right inLetters read simultaneously 5
the reading of letters. Rather, the identity of letters is processed simultaneously acrossseveral horizontal positions with differing efficiency.

Letters read simultaneously 6References
Coltheart, M., Rastle, K., Perry, C., Langdon, R., & Ziegler, J. (2001). DRC: A dual routecascaded model of visual word recognition and reading aloud. Psychological Review,
108, 204–256.
Pelli, D. G., Farell, B., & Moore, D. C. (2003). The remarkable inefficiency of word
recognition. Nature, 423, 752–756.
Peressotti, F., & Grainger, J. (1995). Letter-position coding in random consonant arrays.
Perception & Psychophysics, 57, 875–890.
Rumelhart, D. E., & McClelland, J. L. (1982). An interactive activation model of context
effects in letter perception: Part 2. The contextual enhancement effect and sometests and extensions of the model. Psychological Review, 89, 60–94.
Schoonbaert, S., & Grainger, J. (2004). Letter position coding in printed word perception:
Effects of repeated and transposed letters. Language and Cognitive Processes, 19,333–367.
Seidenberg, M. S., & Plaut, D. C. (1998). Evaluating word-reading models at the itemlevel: Matching the grain of theory and data. Psychological Science, 9, 234–237.
Stevens, M., & Grainger, J. (2003). Letter visibility and the viewing position effect invisual word recognition. Perception & Psychophysics, 65, 133–151.
Tydgat, I., & Grainger, J. (2009). Serial position effects in the identification of letters,digits, and symbols. Journal of Experimental Psychology: Human Perception andPerformance, 35, 480–498.
Whitney, C. (2001). How the brain encodes the order of letters in a printed word: TheSERIOL model and selective literature review. Psychonomic Bulletin & Review, 8,221–243.

Letters read simultaneously 7
Whitney, C., & Cornelissen, P. (2007). SERIOL reading. Language and Cognitive Processes,23, 143–164.

Letters read simultaneously 8Author Note
This work was funded by ESRC Grant RES-062-23-0545. We thank Zach Estes forhelpful comments.

Letters read simultaneously 9Footnotes
1 This procedure is identical to the Adelman and Brown study cited by Whitney andCornelissen (2007), although the design differs.
2 The by-items analyses are based on target-foil pairings, treating reversals asdifferent.

Letters read simultaneously 10
Figure CaptionsFigure 1. (a) Sequence of events in an experimental trial. Participants indicated their
response with the left- or right-hand button on a button box. (b) Accuracy ofidentification for choice between two alternatives differing in 1st (e.g., sung vs. lung), 2nd(e.g., salt vs. silt), 3rd (e.g., buns vs. buys), or 4th (e.g., fish vs. fist) position, for displays
lasting 18 or 24 ms. Error bars are 95% central confidence intervals on the basis of alogistic mixed effects model on the relevant conditions with random slopes per subject up
to the position by duration interaction, and random slopes per item up to the duration
effect (this model matches the design of the experiment under the assumption of random
subjects and items).

(b)
(a)

900−1100 ms.65##########

Accuracy

12−54 ms

lung

.60

.55

6 ms.50

1st

until
response##########
lung

sung

2nd

3rd

Critical Letter Position

4th