A Bayesian approach to the evolution of perceptual and cognitive systems

We describe a formal framework for analyzing how statistical properties of natural environments and the process of natural selection interact to determine the design of perceptual and cognitive systems. The framework consists of two parts: a Bayesian ideal observer with a utility function appropriate for natural selection, and a Bayesian formulation of Darwin’s theory of natural selection. Simulations of Bayesian natural selection were found to yield new insights, for example, into the co-evolution of camouflage, color vision, and decision criteria. The Bayesian framework captures and generalizes, in a formal way, many of the important ideas of other approaches to perception and cognition

Some Distributional Facts about Fricatives and a Perceptual Explanation

Across and within languages voiced sibilants tend to be disfavored relative to voiceless ones. This paper explores the claim that voicing more adversely affects the distinctive acoustic properties of sibilants than those of nonsibilants. One prediction associated with this claim is that voicing differentially lowers the amplitude of frication noise for sibilants and non-sibiliants so that amplitude differences between the two classes are reduced. Acoustic measurements confirm this prediction. A second prediction is that voicing has a greater negative effect on the identification of sibilants than nonsibilants. Perceptual results from this and previous studies are somewhat variable, but averaged data support this prediction. The findings suggest that voiced sibilants are disfavored in part for perceptual reasons

Generalizing a Neuropsychological Model of Visual Categorization to Auditory . . .

This article reports the results of an auditory vowel categorization experiment in which listeners classified 54 synthetic vowel stimuli that varied along the F2 and F3 dimensions into one of three vowel categories, /I/, /U/, and //. A successful, neuropsychologically plausible model of categorization in the visual domain, the SPC, was generalized to the auditory domain and was applied separately to each listener's data from the auditory vowel categorization task. A version of the SPC that assumed two striatal units per category, and thus piecewise linear response region partitions, provided a good description of the data, accounting on average for 97% of the variance in the data. This finding is important because it suggests that a model with a reasonable neurobiological architecture can be applied in both the visual and auditory domains. This provides an important step toward bridging the gap between visual and auditory categorization and toward a neurobiological understanding of the systems involved in these two different, but related, forms of categorization. A version of logistic regression that assumed nonlinear response region partitions (NAPP-NLLR) provided a better account of the data than a version that assumed linear partitions (NAPP-LLR). The linear versions of the SPC and NAPP provided approximately equal accounts of the data, although there was a slight but consistent advantage for the NAPP-LLR model. The nonlinear version of logistic regression (NAPP-NLLR) on the other hand provide a larger and consistent performance improvement in AIC fit over the piecewise linear version of the SPC. Despite the large AIC difference, the predictive power of the models was approximately equal. Specifically, we computed the absolute value of the deviation between predicted..

Auditory Discontinuities Interact with Categorization: Implications for Speech Perception

Behavioral experiments with infants, adults, and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by voice onset time (VOT). Here, it is investigated how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize nonspeech stimuli that mimicked certain temporal properties of VOT stimuli. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. Evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote distinctiveness among sounds within a language inventory. The present data suggest that discontinuities interact with category learning. As such, ‘‘learnability’’ may play a predictive role in selection of language sound inventories

Speech Perception

This chapter focuses on one of the first steps in comprehending spoken language: How do listeners extract the most fundamental linguistic elements— consonants and vowels, or the distinctive features which compose them—from the acoustic signal? We begin by describing three major theoretical perspectives on the perception of speech. Then we review several lines of research that are relevant to distinguishing these perspectives. The research topics surveyed include categorical perception, phonetic context effects, learning of speech and related nonspeech categories, and the relation between speech perception and production. Finally,we describe challenges facing each of the major theoretical perspectives on speech perception