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Experimental Brain Research ISSN 0014-4819Volume 233Number 9 Exp Brain Res (2015) 233:2581-2586DOI 10.1007/s00221-015-4324-7

Similar frequency of the McGurk effect inlarge samples of native Mandarin Chineseand American English speakers

John F. Magnotti, Debshila Basu Mallick,Guo Feng, Bin Zhou, Wen Zhou &Michael S. Beauchamp

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Exp Brain Res (2015) 233:2581–2586DOI 10.1007/s00221-015-4324-7

RESEARCH ARTICLE

Similar frequency of the McGurk effect in large samples of native Mandarin Chinese and American English speakers

John F. Magnotti1 · Debshila Basu Mallick2 · Guo Feng3 · Bin Zhou3 · Wen Zhou3 · Michael S. Beauchamp1

Received: 9 December 2014 / Accepted: 13 May 2015 / Published online: 4 June 2015 © Springer-Verlag Berlin Heidelberg 2015

and stimuli, we found similar frequencies of the McGurk effect between Chinese and American participants (48 vs. 44 %). In both groups, we observed a large range of fre-quencies both across participants (range from 0 to 100 %) and stimuli (15 to 83 %) with the main effect of culture and language accounting for only 0.3 % of the variance in the data. High individual variability in perception of the McGurk effect necessitates the use of large sample sizes to accurately estimate group differences.

Keywords McGurk effect · Cultural differences · Audiovisual speech · Multisensory integration

Introduction

Humans around the world communicate by speaking and listening face-to-face. During these interactions, we inte-grate the heard speech sounds with the seen mouth move-ments to increase both the speed (van Wassenhove et al. 2005) and accuracy (Sumby and Pollack 1954) of speech perception. A common way to assess multisensory integra-tion during speech perception is an illusion known as the McGurk effect (McGurk and MacDonald 1976) in which individuals presented with incongruent auditory and visual syllables report hearing an entirely different syllable. The McGurk effect has become a popular assay of multisensory speech perception because it is easy to administer: Both the stimulus and the response consist of only a single syllable. However, some individuals do not experience the effect and instead perceive the auditory or visual component of the stimulus (Nath and Beauchamp 2012; Stevenson et al. 2012). These individual differences are consistent across test–retest intervals of 12 months or longer, suggesting that they reflect stable differences in the propensity to integrate

Abstract Humans combine visual information from mouth movements with auditory information from the voice to recognize speech. A common method for assessing multi-sensory speech perception is the McGurk effect: When pre-sented with particular pairings of incongruent auditory and visual speech syllables (e.g., the auditory speech sounds for “ba” dubbed onto the visual mouth movements for “ga”), individuals perceive a third syllable, distinct from the audi-tory and visual components. Chinese and American cul-tures differ in the prevalence of direct facial gaze and in the auditory structure of their languages, raising the possibility of cultural- and language-related group differences in the McGurk effect. There is no consensus in the literature about the existence of these group differences, with some studies reporting less McGurk effect in native Mandarin Chinese speakers than in English speakers and others reporting no difference. However, these studies sampled small numbers of participants tested with a small number of stimuli. There-fore, we collected data on the McGurk effect from large samples of Mandarin-speaking individuals from China and English-speaking individuals from the USA (total n = 307) viewing nine different stimuli. Averaged across participants

Electronic supplementary material The online version of this article (doi:10.1007/s00221-015-4324-7) contains supplementary material, which is available to authorized users.

* John F. Magnotti magnotti@bcm.edu

1 Department of Neurosurgery, Baylor College of Medicine, 1 Baylor Plaza, Suite 104, Houston, TX, USA

2 Department of Psychology, Rice University, Houston, TX, USA

3 Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China

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auditory and visual speech information (Basu Mallick et al. 2015).

Although many laboratory studies of psychological phenomena focus exclusively on native English speakers, the McGurk effect is an important exception. It has been studied across native speakers of Mandarin Chinese, Can-tonese, Thai, and Japanese (Burnham and Lau 1998; Chen and Hazan 2007; Sekiyama 1997; Sekiyama and Tohkura 1991), Spanish, German, Hungarian (Fuster-Duran 1996; Grassegger 1995), Italian (Bovo et al. 2009), Finnish (Sams et al. 1998; Traunmüller and Öhrström 2007), and Hebrew (Aloufy et al. 1996). The groups in these studies are defined both by cultural differences and by differences in their native language; in this paper, we group them and refer to them together as “intercultural.”

The strongest claim in the literature for intercultural differences in the McGurk effect involves comparisons between Asian and non-Asian cultures. Sekiyama and Tohkura (1991, 1993) reported a lower frequency of McGurk perception in native Japanese speakers than in native English speakers, and equal or lower frequency in Mandarin Chinese speakers than in Japanese speakers (Hayashi and Sekiyama 1998; Sekiyama 1997). In agree-ment with these results, Burnham and Lau (1998) found a lower frequency of McGurk perception in Cantonese speakers than in English speakers.

Two major groups of hypotheses have emerged to explain intercultural differences in the McGurk effect. The linguistic hypothesis explains them via the properties of Asian languages. Tonal languages (such as Mandarin) and semi-tonal languages (such as pitch accents in Japanese) may increase reliance on auditory speech cues, decreas-ing the relevance of visual speech information (Sekiyama 1997). Phonemes of Mandarin and Japanese may be easier to discriminate without visual cues than those of English, reducing the need for visual speech information to disam-biguate speech sounds (Sekiyama and Burnham 2008). The face avoidance hypothesis explains them via the cultural milieu of the listener. In Japanese and Chinese cultures, direct viewing of the face is considered impolite and hence discourages people in these cultures from developing a strong reliance on the visual speech information required for perception of the McGurk effect (Sekiyama 1997). There is some evidence that English-speaking children are better at visual-only identification of speech than Japanese children (Sekiyama and Burnham 2008).

One potential problem with these findings of intercul-tural differences is that they were conducted before recent advances in our understanding of individual differences in the McGurk effect. Some native English speakers never perceive the illusion and others always perceive it (Mag-notti and Beauchamp 2014; Basu Mallick et al. 2015; Nath and Beauchamp 2012; Stevenson et al. 2012; Strand et al.

2014). High variability means that large sample sizes are necessary for accurate statistical inference, but many stud-ies of cultural differences in the McGurk effect have used small sample sizes (e.g., 10–14 participants, Bovo et al. 2009; Sekiyama 1994, 1997), possibly resulting in infer-ential errors. For instance, in a random sample of 14 par-ticipants, eight might always perceive the illusion and six might never perceive it, resulting in an estimate of the mean frequency of the illusion of 57 %. A second random sample of 14 participants from the same population might find 10 who always perceive the illusion and five who never do, resulting in a mean estimate of 71 %. This 14 % difference in the estimates of the mean from the same population is similar to some reported estimates of cultural differences in the McGurk effect (Sekiyama 1994). Supporting this idea, some studies comparing English and Chinese speak-ers have not found differences in McGurk frequency (Chen and Hazan 2007, 2009).

Another difficulty in interpreting the literature is that stimuli from different talkers (or even different stimuli from the same talker) vary greatly in their ability to evoke the McGurk effect (Jiang and Bernstein 2011; Magnotti and Beauchamp 2014; Basu Mallick et al. 2015). This vari-ability is problematic when cross-cultural studies use stim-uli created from only two talkers (Bovo et al. 2009; Burn-ham and Lau 1998; Hayashi and Sekiyama 1998; Sekiyama 1994, 1997; Sekiyama and Tohkura 1993). Just as testing a small group of participants from a highly variable popula-tion is problematic, testing only a few McGurk stimuli can also lead to errors in inference due to idiosyncratic effects of individual talkers.

To overcome these difficulties, we compared McGurk perception between a large sample of Mandarin-speaking individuals from China (n = 162) and a large sample of English-speaking individuals from the USA (n = 145) using a battery of nine McGurk stimuli from eight different talkers. The use of a large sample of participants and stim-uli allowed us to better estimate the magnitude of cultural differences in the McGurk effect.

Methods

Chinese participants

All participants gave written informed consent to partici-pate in an experimental protocol approved by the Institu-tional Review Board of the Institute of Psychology of the Chinese Academy of Sciences. Parental informed consent was obtained for participants under 18 years of age. Partici-pants consisted of 162 Mandarin speakers native to China (82 female; mean age = 17 years, range 14–23) recruited from the Beijing Twin Study project of the Institute of

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Psychology of Chinese Academy of Sciences (analysis was only conducted on the first-born of each twin pair). All par-ticipants reported normal or corrected-to-normal vision and no history of speech, language, or hearing difficulties.

American participants

All participants gave written informed consent to partici-pate in an experimental protocol approved by the Institu-tional Review Board of Rice University. All participants were native to the USA and reported English as their pri-mary language (n = 145, 97 female, mean age = 19 years, range 18–26). All participants reported normal or cor-rected-to-normal vision and no history of speech, language, or hearing difficulties.

Stimuli and procedure

The McGurk stimuli consisted of nine audiovisual record-ings, lasting 2 s each (see Supplemental Table 1). Each stimulus contained an auditory recording of a syllable and a video recording of the face of the same talker enunciat-ing a different syllable. Four stimuli consisted of auditory “ba” and visual “ga” (AbaVga). Three stimuli consisted of double syllables, auditory “baba” paired with visual “gaga” (AbabaVgaga). Two stimuli consisted of auditory “pa” and visual “ka” (ApaVka). There were five male speakers and three female speakers (the same female speaker appeared in two stimuli). Stimuli were viewed at a distance of 40 cm and filled a 15″ LCD display.

During the experiment, the stimuli were presented in random order. Participants in the China group saw each McGurk stimulus eight times; participants in the USA group saw each McGurk stimulus 10 times, but we ana-lyzed only the first eight presentations to match the China group (the results were unchanged when all 10 presenta-tions were analyzed).

Participants reported their percepts by speaking aloud and no feedback was given. Responses were recorded by the stimulus computer and transcribed by a research assis-tant. The USA group also viewed control stimuli (10 times each) intermixed with the McGurk stimuli: six congru-ent audiovisual syllables (“ba,” “ga,” “pa,” “ka,” “da,” and “ta”) and two non-McGurk incongruent stimuli, which are similar to McGurk stimuli, but with the auditory and visual constituents reversed (AgaVba and AkaVpa) all spoken by the same female speaker.

Scoring responses

Responses to McGurk stimuli were categorized as follows. The responses “da” or “tha” (to AbaVga) and “ta” or “tha” (to ApaVka) were categorized as McGurk fusion responses.

The responses “ba” (to AbaVga) and “pa” (to ApaVka) were categorized as auditory responses. The responses “ga” (to AbaVga) and “ka” (to ApaVka) were categorized as visual responses. Any other response was categorized as “other.” For AbabaVgaga stimuli, each syllable was coded separately (e.g., the response “dada” was coded as 1.0 McGurk; the response “bada” was coded as 0.5 McGurk and 0.5 auditory).

Across all subjects and stimuli, the McGurk responses (46 %) and auditory responses (37 %) were the most com-mon. Visual responses (7 %) and “other” responses (10 %) were comparatively rare across stimuli and individuals. Only two stimuli had visual responses more than 15 % of time, and only two stimuli had “other” responses more than 15 % of time. This pattern of responding led to com-plementary percentages between McGurk and auditory responses, and thus, we analyzed only McGurk responses to each stimulus.

Results

We compared the frequency of the McGurk effect in native Mandarin-speaking individuals from China and native Eng-lish-speaking individuals from the USA across nine stimuli (Fig. 1a). The overall frequency of McGurk responses for the China group (mean = 48 %, standard error of the mean, SEM = 2 %) was slightly greater than for the USA group (mean = 44 %, SEM = 2 %), although the difference was not statistically significant [t(305) = 1.29, p = 0.20]. In both groups, there was high variability across participants, with some participants in both groups never perceiving the illusion (0 %) and some from both groups always perceiv-ing the illusion (100 %). There was also a large range of effectiveness across the different stimuli. The weakest stim-ulus evoked the McGurk effect 15 % of the time (averaged across all participants), while the strongest stimulus evoked the McGurk effect 83 % of the time (Fig. 1b).

To examine this variability statistically, we performed a 2 × 9 repeated-measures analysis of variance (RM ANOVA) with stimulus (within subjects) and cultural group (between subjects) as factors and percentage McGurk responses as the dependent measure. There was no main effect of cultural group [F(1, 305) = 1.7, p = 0.20, generalized η2 = 0.003]. Given the wide range of effectiveness across stimuli, it was unsurprising to find a main effect of stimulus [F(8, 2440) = 194.2; p = 10−254, generalized η2 = 0.24)]. Look-ing across stimuli, there were three stimuli for which the USA group had a higher fusion percentage and six for which the China group had a higher fusion percentage. In the RM ANOVA, this manifested itself as a robust, though weak (in terms of effect size) interaction between group and stimu-lus [F(8, 2440) = 15.4; p = 10−22, generalized η2 = 0.02]. Therefore, we performed post hoc t tests between the two

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languages for each individual stimulus. After correcting for the multiple comparisons across nine stimuli using a Bonfer-roni correction, only two stimuli showed significant differ-ences, both with a higher frequency of McGurk percepts in the China group [stimulus 7: t(305) = 6.4, p = 10−8; stimu-lus 8: t(305) = 3.8, p = 0.002].

The two stimuli showing a significant difference between groups did not share any common features. Stimu-lus 7 was a male Caucasian talker speaking AbaVga, while stimulus 8 was a female Asian talker speaking ApaVka. Conversely, grouping stimuli according to shared features failed to explain group differences. For instance, stimuli with Caucasian talkers had different response profiles (e.g., USA > CH for stimulus 4 vs. USA < CH for stimulus 7), as did stimuli with the same Asian talker (USA ≅ CH for stimulus 1 vs. USA < CH for stimulus 8).

Discussion

In a sample of 307 individuals and nine stimuli, we found similar frequencies of the McGurk effect in native

Mandarin speakers from China and native English speak-ers from the USA. In each group, we found high variabil-ity across participants (range from 0 to 100 %) and stimuli (15–83 %). Our large sample size allows us to accurately estimate the size of any possible cultural difference in the McGurk effect. We found that the main effect of cultural group accounted for only 0.3 % of variance in the fre-quency of McGurk perception and the interaction between cultural group and stimulus accounted for only 2 % of the variance.

Although this may be viewed as a negative finding—no significant difference between groups—the publica-tion of null results is critical for theory testing. Publishing only positive group differences prevents the falsification of theories that predict such differences (Ferguson and Heene 2012; Kuhberger et al. 2014; Pashler and Wagenmakers 2012). This problem may be particularly acute in the lit-erature on the McGurk effect, because the large variability in individual susceptibility to the illusion makes it impos-sible to precisely estimate McGurk frequency using the small sample sizes (less than 15 per group) used in many previous studies (Bovo et al. 2009; Burnham and Lau 1998;

Stimulus #

% McGurk % McGurk

ba

c

p = 0.2

CH US

CH US

1 2 3 4 5 6 7 80

50

* *100

0

50

100

9

1 2

6 7 8

3 4

9

5

Fig. 1 a Overall percentage of McGurk fusion responses for native Mandarin speakers from China (n = 162; orange) and native English speakers from the USA (n = 145; blue). Reported p value is for the t test on McGurk percentage between groups. b McGurk percentage for each stimulus and group. Stimuli are arranged by overall McGurk

percentage. Asterisks indicate significant differences between groups (p < 0.05; Bonferroni-corrected for multiple comparisons). c Still frames from each stimulus, arranged as in b. The numbers in the top left of each frame show the stimulus # and were not visible to partici-pants (color figure online)

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Sekiyama 1994, 1997). For instance, a study with 15 par-ticipants per group would have only 18 % power to detect a 10 % difference in the frequency of the McGurk effect across cultures. In contrast, the current study (with an approximately ten times larger n) had 83 % power to find group differences as small as 10 %.

Our finding of similar frequencies of McGurk perception in native Mandarin and native English speakers supports other evidence that the fundamentals of speech perception are similar between the two groups (Chen and Hazan 2009; Hazan et al. 2010) but rebuts theories of speech perception predicated on cultural differences. Both linguistic and cul-tural hypotheses predict a lower frequency of the McGurk effect in Chinese participants, but we found a higher (though nonsignificant) frequency of the McGurk effect in Chinese participants. Of course, we cannot rule out differ-ences in the direction predicted by the linguistic and cul-tural hypotheses for other groups, such as native Japanese speakers (Sekiyama and Tohkura 1991, 1993).

Another possible reason for the observed difference between our work and earlier studies (Sekiyama and Tohkura 1991, 1993) is the different generations being sampled. Our sample of Chinese listeners is younger and grew up in a different societal context than those in stud-ies from the late twentieth century. Because of increasing globalization, younger individuals in a rapidly modernizing country may be less susceptible to the mores and customs of previous generations and more in tune with a global youth culture (de Sousa 2011). Thus, the face avoidance hypothesis may still be viable for some portion of the Chi-nese population, but not within the young adults tested in the current study.

Individual differences in the McGurk effect are related to differences in the pattern of eye movements made when viewing talking faces (Gurler et al. 2015), and the fre-quency of the McGurk effect correlates with an individual’s visual speech reading ability (Strand et al. 2014). Reduced visual abilities such as those found in amblyopia are linked to reduced frequency of the McGurk effect in chil-dren (Burgmeier et al. 2015) and adults (Narinesingh et al. 2014). Even in healthy subjects, responses to the McGurk effect may depend on task instructions. For instance, the instructions “what did the talker say” might be more likely to elicit the effect than “what did you hear, ignoring the talker’s face.”

Conclusion

Without a better understanding of what stimulus features are most important for evoking the McGurk effect (Jiang and Bernstein 2011), a model of how these stimulus fea-tures are used (Ma et al. 2009; Magnotti and Beauchamp

2014), and a clear hypothesis about why individuals from different groups might be more or less sensitive to those features (Hazan et al. 2010), it remains difficult to interpret reports of greater or lesser frequencies of McGurk percep-tion in any given culture, especially when only a few stim-uli are used. These concerns also apply to studies that com-pare McGurk perception across different groups, whether the groups are defined by age (Hockley and Polka 1994; McGurk and MacDonald 1976; Rosenblum et al. 1997), gender (Aloufy et al. 1996; Irwin et al. 2006; Traunmüller and Öhrström 2007), or clinical diagnosis (de Gelder et al. 2003; Delbeuck et al. 2007; Mongillo et al. 2008). Our results illustrate two important points. First, high individual variability in the McGurk effect necessitates large sample sizes to estimate group differences precisely. Second, the high variability across stimuli requires testing with varied stimuli to measure across-stimulus differences and interac-tions between group and stimulus.

Acknowledgments This research was supported by NIH R01NS065395 to MSB.

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