![]() ![]() ![]() Now ask them to listen for ba in your speech. They will know what you said, but will not know what the sounds were. Here's why it makes a difference: the next time you are talking to someone, stop at some point and ask them whether you uttered the syllable ba in the last sentence. No wonder all these studies find effects in the frontal lobe! What are the implications for neuroscience studies of speech perception? Well, if CP is nothing more than task effects and/or subject bias, then by using CP paradigms to map speech perception systems, all that is being mapped is task strategies and/or subject bias. His work on the topic is also worth a look. Then there's always long-time CP skeptic Dominic Massaro. paper for more critical views on the nature of categorical perception. Have a look at the papers by Lori Holt and Andrew Lotto that I highlighted in a previous post as well as the Schouten et al. Instead we see a more continuous function. We should see discontinuities in the cumulative d'. To do this you can calculate d' for each pair of adjacent stimuli (how well are Ss discriminating Stim1 from Stim2, Stim2 from Stim3, etc.). The vertical access is proportion of GA responses, and the horizontal axis is the various stimuli along the continuum. Nonetheless, use of d-prime measures shows a rather different picture to standard measures. if the nature of the task compels subjects to use a labelling strategy, categorical perception will be pretty much a foregone conclusion" (p. This is not a good task to determine whether subjects perceive speech sounds categorically because it forces them to categorize. The task is explicitly categorical: subjects are asked to decide whether a stimulus is an example of GA or DA. The graph below shows real data from a CP experiment using a GA-DA continuum. Let me illustrate very simply using some categorical perception data that I pulled from the literature. This is an interesting paper that is worth a close look. categorical perception has in practice remained an ill-defined or even undefined concept, which could be used to underpin a variety of sometimes mutually exclusive claims, for example for or against the motor theory (p. Here's another interesting quote from this paper:ĭespite an auspicious beginning with a clear experimental definition. The traditional categorical-perception experiment measures the bias inherent in the discrimination task ![]() The point of the paper is exactly was I was hinting at: perception only looks categorical because of inherent bias in the tasks used to measure it. 2003, provocatively titled "The End of Categorical Perception as We Know It". Lori Holt recently pointed me to a paper by Schouten et al. I hinted previously that the failure to use signal detection analysis methods in the context of categorical perception studies may have contaminated the whole field of CP research. Neural correlates of categorical perception in learned vocal communication. Prather JF, Nowicki S, Anderson RC, Peters S, Mooney R. Electrophysiological markers of categorical perception of color in 7-month old infants. 2009Ĭlifford A, Franklin A, Davies IR, Holmes A. Sounds: A step toward biological plausibility. Modeling the categorical perception of speech Motor representations of articulators contribute toĬategorical perception of speech sounds. Interest in categorical perception (CP) faded - except in neuroscience where the pace of CP studies seems to be accelerating. Further, perception of speech sounds was found to be continuous if listeners were asked to rate how well a stimulus represented a given category rather than asking them to make a binary decision. Categorical perception of non-speech sounds was also demonstrated. Babies too, who hadn't yet acquired the ability to articulate speech, also exhibited categorical perception. Non-human, and therefore non-speaking, animals such as chinchillas and quail, were found to exhibit categorical perception for speech sounds. Therefore we perceive speech via our motor system. Perception mirrors the categorical nature of articulation. Articulatory patterns are categorical (/b/ is always produced bilabially). Listeners appeared to perceive speech sounds differently from non-speech sounds, i.e., categorically, and this was taken as evidence for the motoric nature of the speech perception process. Back in the motor theory heyday, categorical perception was all the rage. The phenomenon of categorical perception appears to be riding the coattails of the resurgence of interest in motor theories of speech perception. Old speech phenomena don't die they just become morphed into neuroscience studies.
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