STIMULUS FAMILIARITY AND ATTENTIONAL EFFECTS ON THE NEURAL ORGANIZATION OF AUDITORY CATEGORICAL PERCEPTION

Breya Walker B.A.2,3 & Gavin M. Bidelman Ph.D.1,2

University of Memphis School of Communication Sciences & Disorders1, Institute for Intelligent System2,Department of Psychology3

INTRODUCTION

REFERENCES

CONCLUSIONSMETHODS

RESULTS DISCUSSION

Participants: 10 adult participants • N=10 (1 male); mean years of training 0.6; mean age of onset

4.1 yrsStimuli and behavioral recording• Speech stimuli

• /u/ to /a/ continuum; 5 tokens (Bidelman et al, 2014)• 100 ms duration

• Music stimuli • Minor (m3) to Major 3rd (M3) interval continuum; 5 tokens• 100 ms duration

• Presentation:• Block design by stimulus set (speech vs. music stimuli)• Block design by listening condition (active vs. passive listening)

Procedure• Subjects identify stimuli during active listening • Subject ignore stimuli during passive listening

Analyses• Mixed model ANOVA: random effect of subject and fixed effect of listening

condition and stimulus category• Paired sample t-test: Assess reaction times (RT) for each stimulus set• Independent samples t-test: assess beta 1 values derived from logistic

function

In the present study, we investigated the influence of attentional state and stimulus

familiarity on the neural and behavioral organization of categorical perception (CP). It has

been shown that behaviorally, CP is evident only when individuals engage with speech stimuli

rather than music. Moreover, reaction times are faster when individuals are more familiar with

a particular stimulus set (i.e., speech). Additionally, brain activity is able to distinguish the

difference between true and ambiguous sound categories. Furthermore, neural activity was

shown to predict individuals’ categorization identification precision during active listening only.

Previous research has reported conflicting results regarding the expression of CP with

researchers indicating CP is exhibited during times of active listening (Bidelman et al., 2013)

and during times of passive listening (Chang et al., 2010). Our results demonstrate that CP is

only exhibited during times of active listening, thus supporting prior research (Bidelman et.

al., 2013). Furthermore, the salience of CP is dependent upon an individuals’ familiarity with a

particular stimulus set. Thus, individuals who lack familiarity with a stimulus set will not have

the ability to make a comparative judgment between contrasting sounds within that domain.

Our results imply that categorical perception exists during times of active engagement with

sounds that are more familiar to a listener.

Werker, J.F., Tees, R.C. (1987). Speech perception in severely disabled and average reading children. Canadian Journal of Psychology, 41, 48–61.

Winkler, I., Kujala, T., Titinen, H., Sivonen, P., Alku, P., Lehtokoski, A., … Näätänen, R. (1999). Brain responses reveal the learning of foreign language phonemes. Psychophysiology, 36, 638-642.

Kuhl, P.K., Williams, K.A., Lacerda, F., Stevens, K.N., Lindblom, B., (1992). Linguistic experience alters phonetic perception in infants by 6 months of age. Science 255, 606–608.

Hillyard, S. A., Hink, R. F., Schwent, V. L., & Picton, T. W. (1973). Electrical signs of selective attention in the human brain. Science 182, 177–180

Zhang, Y., Kuhl, P.K., Imada, T., Kotani, M., & Tohkura, Y. (2005). Effects of language experience: Neural commitment to language-specific auditory patterns. NeuroImage, 26, 703–720.

Chang, E.F., Rieger, J.W., Johnson, K., Berger, M.S., Barbaro, N.M., Knight, R.T. (2010). Categorical speech representation in human superior temporal gyrus. Nature Neuroscience, 13, 1428–1432.

Bidelman, G.M., Moreno, S., Alain, C., (2013). Tracing the emergence of categorical speech perception in the human auditory system. Neuroimage, 79, 201-212.

1. The expression and salience of CP is contingent upon attention and stored auditory information, respectively

2. How well individuals’ perform in identifying speech or music sounds is based on their neural activity that occurs 100-200 ms after sound is presented

Categorical perception (CP) is reflective of the ability to make a comparative judgment

based on stored auditory information. Regarding audition, CP has been shown to influence

perceptual processes such as language acquisition, reading, and writing (Werker & Tees, 1984;

Winkler et. al., 1999). Prior research has shown that CP is an innate ability and its expression is

impacted by attention and familiarity with a particular stimulus category (Kuhl et. al., 1992;

Hillyard et. al., 1973; Zhang et. al., 2005). However, these factors known to impact CP (i.e.,

attention and familiarity) have been assessed separately within the literature. Due to

investigations occurring separately, conflicting research has emerged. Particularly, some

researchers suggest that the expression of CP to speech sounds requires attention (Bidelman et

al., 2013), while others suggest that CP to speech sounds occurs during passively (Chang et. al.,

2010). Moreover, there is a paucity of research that has examined CP within other stimulus

domains (i.e., music).

The current investigation served to examine the influence of stimulus familiarity and

attention on the expression and salience of CP. We acquired behavioral and neural measures in

order to assess the degree to which CP is impacted by the aforementioned factors. We

anticipated that the expression and salience of CP would be impacted by attention and familiarity,

respectively.

Mixed Model ANOVA assessing neural activity to speech sounds and attentional state

Neural activity stronger during passive vs, active listening: t (9) = -3.08, p = 0.013

Neural activity was similar to true categories regardless of listening state: t (9) = -0.52, p = 0.613

Neural activity was similar between true and ambiguous categories during passive listening: t(9) = -1.12, p = 0.2934

Paired sample t-test assessing RT to each stimulus category

RTs faster for true speech categories vs. ambiguous speech categories: t(9) = 3.49, p = 0.007 (M= 427.1, SD= 96.5 vs. M =490.1, SD =101.1)

RTs slower for true music categories vs. ambiguous music categories: t(9) = -2.96, p = 0.018 (M= 478.1, SD= 142.7 vs. M =456.2, SD =128.6)

Independent samples t-test assessing behavioral identification

Speech sounds perceived more categorically than music sounds: t (9) =26.868, p < 0.001

*No main effects of stimulus category, attention state, or interaction were seen within the music domain

Music

Time(ms)

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Token 1/5 (active)Token 3 (active)Token 1/5 (passive)Token 3 (passive)

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