Abstract # 2752 Event # 25:

Scheduled for Saturday, September 19, 2009 10:45 AM-10:55 AM: Session 3 (Del Mar Room) Oral Presentation


WORD RECOGNITION IN THE ABSENCE OF TRADITIONAL ACOUSTIC CUES BY A LANGUAGE-TRAINED CHIMPANZEE (PAN TROGLODYTES)

L. A. Heimbauer1,2, M. J. Beran1,2 and M. J. Owren1,2
1Georgia State University, Lisa A. Heimbauer, Department of Psychology, P. O. Box 5010, Atlanta, GA 30302-5010, USA, 2The Language Research Center
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The human ability to understand even incomplete or distorted speech is argued to be evidence of specialized, species-specific processing. Two experiments therefore tested for this capability in Panzee, a 22-year-old language-trained chimpanzee. Panzee was of particular interest because she was reared from infancy by human caregivers who spoke to her as they would to a human infant, and because she can identify more than 100 spoken words using graphical symbols (lexigrams). Tests were conducted via computer with two different sets of 24 familiar words presented one-per-trial in either natural versus an incomplete, “voiced-only” synthetic form (Experiment 1), or natural versus a strongly distorted “noise-vocoded” synthetic form (Experiment 2). Each session included 4 blocks of 24 trials, with 16 natural and 8 synthetic words in each block. Each word set was tested for 3 sessions, systematically varying the synthetic words presented. When hearing a word, Panzee chose the corresponding lexigram from among four alternatives. One-tailed t-tests showed that mean percentage-correct with natural words exceeded the chance rate of 25% correct in each experiment, including 87% [t(23)=14.7; p<0.001] and 86% [t(23)=18.9; p<0.001], respectively. Performance with voiced-only and noise-vocoded words was also statistically above chance, 80% [t(23)=15.4; p<0.001] and 53% [t(23)=6.72; p<0.001], respectively. Results show that experience with speech can produce functional perception in the absence of traditional acoustic cues, and that specialized processing mechanisms are unnecessary.