Poor sensitivity to sound statistics impairs the acquisition of speech categories in dyslexia

ABSTRACT

Accumulative studies suggest that people with dyslexia have impaired categorical perception of speech. However, the origin of this deficit remains unknown. We now propose that impaired sensitivity to distributional statistics in dyslexia underlies this deficit. This proposal is based on the following rationale. The literature on acquiring speech categories in the general population attributes a major role to learning distributional statistics. Sensitivity to the statistics of stimuli used in perceptual discrimination tasks is impaired in dyslexia. Specifically, dyslexics’ implicit memory of previous stimuli decays faster than that of good readers and their stimulus-specific adaptation processes are shorter. Their faster decay may limit the temporal window over which they implicitly calculate stimulus distributions, and yield slightly impoverished speech categories. Since impaired sensitivity to stimulus statistics and impaired categorisation in dyslexia are domain general, we further propose that impaired categorical speech perception is one manifestation of a broader deficit in distributional learning.

KEYWORDS:

• Reading
• speech perception
• adaptation processes
• anchoring hypothesis
• skill acquisition
• Bayesian inference

Acknowledgements

We thank Bracha Nir for comments and discussion of the ideas presented in this review.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported an Israel Science Foundation (ISF 112/13) grant to Karen Banai and Rachel Yifat, a Canada–Israel ISF grant to Robert Zatorre and Merav Ahissar and a German-Israeli Foundation for Scientific Research and Development grant to Stefan Koelsch and Merav Ahissar.