PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Fundamental research on the verbal transformation effect inJapaneseSeiya FUNATSU1; Masako FUJIMOTO2
1

Prefectural University of Hiroshima, Japan
2

Waseda University, Japan

ABSTRACTThe verbal transformation effect is a phenomenon that occurs when a person hears a repeated single word
without pause and illusory changes in the physically unchanging word are induced. There are few studies ofthe verbal transformation effect in Japanese. Therefore, in this study, we examine whether the verbal
transformation effect occurs with respect to changes in the inter stimulus interval (ISI) in Japanese. The
studied ISIs were 0 sec, 0.02 sec, 0.05 sec, 0.1 sec, and 0.15 sec. The subjects were 16 native Japanese
university students. The stimuli consisted of a word with three syllables. We found that the perceptual
transition time changed with changes in the ISI. “The number of perceived stimuli” until the perceptual
transition occurred was 24.7 for an ISI of 0 sec but 57.4 for an ISI of 0.15 sec. ANOVA showed a significanteffect for “the number of perceived stimuli” (F(4,73) = 2.585 (p = 0.0439)). Moreover, a post hoc test
revealed that “the number of perceived stimuli” for an ISI of 0.15 s was significantly larger than that for an
ISI of 0 sec (p = 0.0051). The mechanisms for the verbal transformation effect are discussed.
Keywords: ISI, Satiation, Delay

1. INTRODUCTION
Listening to repetitions of a single word without a pause induces illusory changes in the physicallyunchanging word. For example, “tress” may be transformed into a variety of verbal forms, such as“dress,” “stress,” “drest,” or even “Esther” (1, 2). This phenomenon is known as the verbal
transformation effect (VTE) (1). Warren has examined the influence of F0, loudness, and noise on theVTE in English (1).
In Japanese, Kondo and Kashino (3) and Kashino and Kondo (4) have studied VTE in terms of brain
science. Using fMRI, they found that the left inferior frontal cortex, the anterior cingulate cortex, andthe left prefrontal cortex are activated during this perceptual transition. Few studies to date, however,
have examined the VTE in terms of behavioral science in Japanese. This is a preliminary study toanalyze the mechanisms of VTE in terms of behavioral science.
The perception of speech is satiated due to repeated activation (2). We examined whether
perceptual transitions occur with and without pauses. In addition, because the state of satiation
changes due to the inclusion of pauses, we also measured how long it takes for perceptual transitions tooccur.

2. METHODS
2.1 Stimuli and subjects
The stimulus was /banana/ uttered by a male native Japanese speaker. /banana/ is an actual Japaneseword for which VTE has been found to occur (3) (Figure 1).
12funatsu@pu-hiroshima.ac.jp
fujimoto1000@hotmail.com

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The subjects were 16 native Japanese university students aged 21–23 (4 males and 12 females). Thesubjects were instructed to listen to the stimulus sequences and then click a button on a computer
display when they perceived a change in the sound.

bananaFigure 1 – Wave form of /banana/
2.2 Procedure
The subjects heard five sequences through their headphones. To avoid influences due to thepresentation order (ISIs of 0 sec, 0.02 sec, 0.05 sec, 0.1 sec, and 0.15 sec), the subjects were divided
into two groups. Each group consisted of eight subjects.
The ascending order (ASC) group heard the stimulus sequences in the following order:/banana/ with a 0-sec ISI, /banana/ with a 0.02-sec ISI, /banana/ with a 0.05-sec ISI, /banana/with a 0.1-sec ISI, and /banana/ with a 0.15-sec ISI.
The descending order (DSC) group heard the stimulus sequences in the following order:/banana/ with a 0.15-sec ISI, /banana/ with a 0.1-sec ISI, /banana/ with a 0.05-sec ISI, /banana/with a 0.02-sec ISI, and /banana/ with a 0-sec ISI.

The start time of the sequences (t 0 ) and the click time (t c) were recorded on a computer, and theperceptual transition time (PTT) was calculated by subtracting t 0 from t c. Then, the number ofperceived stimuli prior to the occurrence of a perceptual transition was calculated via the following
formula:the number of perceived stimuli = PTT / (stimulus length + ISI), where the stimulus length was
0.365 sec.
The values of “the number of perceived stimuli” obtained from the individual subjects wereaveraged for each ISI. After the perception tests were completed, we asked each subject what they
perceived the sound to be.

3. RESULTS
In the case of the DSC group, a perceptual transition did not occur for one subject for ISIs of 0.1 sec
and 0.15 sec. Figure 2 shows the results for the ASC group, and Figure 3 shows those for the DSC
group. In the case of the 0-sec ISI, “the number of perceived stimuli” for the ASC group was 31.0 andthat for the DSC group was 18.5. In the case of the 0.15-sec ISI, “the number of perceived stimuli” forthe ASC group was 55.3 and that for the DSC group was 59.7. Namely, in the cases of 0-sec and0.15-sec ISI, “the number of perceived stimuli” in the ASC group did not differ from that in the DSC5704

The number of perceived stimuligroup. An ANOVA with two factors, Order and ISI, was performed. The ANOVA showed a significant
main effect for the ISIs (F(4,68) = 2.802 (p = 0.0324)) but not for the Orders (F(1,68) = 2.025 (p =0.1593)) and for the interaction (F(4,68) = 2.0166 (p = 0.1020)). The Order was not significant;therefore, the data from the ASC and DSC groups were pooled (Figure 4). In these pooled data, anANOVA showed significant difference for the ISI (F(4,73) = 2.585 (p = 0.0439)). The post hoc test
showed a significant difference between the 0-sec ISI and the 0.15-sec ISI (p = 0.0051).

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0.05

0.10.15

ISI (sec)

The number of perceived stimuli

Figure 2 – The effect of ISI in the ascending order group7060
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ISI (sec)

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Figure 3 – The effect of ISI in the descending order group5705

The number of perceived stimuli

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0.05
ISI (sec)

0.1

0.15

Figure 4 – The effect of ISI in the pooled data

4. DISCUSSION
A perceptual transition occurred when the ISI was 0.02–0.15 sec. As the ISI lengthened, there wasan increase in “the number of perceived stimuli.” The stimulus length of /banana/ was 0.365 sec(Figure 1). When the ISI was 0 sec, subjects heard the stimulus approximately 24.7 times before aperceptual transition occurred; however, when the ISI was 0.15 sec, they heard it approximately 57.4
times before a perceptual transition occurred. Therefore, the subjects needed to hear more stimuli
before the perceptual transition when the ISI was 0.15 sec than when it was 0 sec. One explanation forthis phenomenon is satiation (2, 5, 3). Subjects satiate when they hear repeated stimuli, which triggers
a criterion shift in the category boundary, which in turn leads to a perceptual transition. According toa study by Efron (6), the speech rate in everyday speech is ~12 phonemes/sec (the length of one CVsyllable is approximately 0.16 sec). The length of one syllable in /banana/ in this study is 0.122 sec(0.365/3). Therefore, an ISI of 0.15 sec is nearly equal to the duration of one syllable. A pause
equivalent to one syllable may delay or relax satiation.

5. CONCLUDING REMARKS
Even though the verbal transformation effect has generally been thought to occur only when there
are no pauses between the repeated stimuli, we found in this study that it occurred in cases of interstimulus intervals (ISI) of 0.02 sec, 0.05 sec, 0.1 sec, and 0.15 sec. When the ISI was 0 sec, 24.74
repetitions of /banana/ were perceived before a perceptual transition occurred. However, when the ISI
was 0.15 sec, 57.4 repetitions of /banana/ were perceived before the transition occurred. Therefore,
an increase in the ISI could result in reduced or relaxed satiation.

REFERENCES
1. Warren RM. Illusory changes of distinct speech upon repetition-the verbal transformation effect. Br J
Psychol. 1961;52(3):249-258.
2. Warren RM. Verbal transformation effect and auditory perceptual mechanisms. Psychol Bull.
1968;70(4):261-270.
3. Kondo HM, Kashino M. Neural mechanisms of auditory awareness underlying verbal transformations.

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Neuroimage 2007;36(1):123-130.
4. Kashino M, Kondo HM. Functional brain networks underlying perceptual switching: auditory streaming
and verbal transformations. Philos Trans R Soc Lond B Biol Sci. 2012;367(1591):977-987.
5. Warren RM. Criterion shift rule and perceptual homeostasis. Psychol Rev. 1985;92(4):574-584.
6. Efron R. Temporal perception, aphasia, and déjà vu. Brain 1963;86(3):403-424.

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