Misperception in sentences but not in words: Speech perception and the phonological buffer

Abstract

We report two case studies of aphasic patients with a working-memory impairment due to reduced storage in the phonological buffer. The two patients display excellent performance in phonological discrimination tasks as long as the tasks do not involve a memory load. We then show that their performance drops when they have to maintain fine-grained phonological information for sentence comprehension: They are impaired at mispronunciation detection and at comprehending sentences involving minimal word pairs. We argue that the phonological buffer plays a role in sentence perception during the phonological analysis of the speech stream: It sustains the temporary storage of phonological input in order to check and resolve phonological ambiguities, and it also allows reexamination of the phonological input if necessary.

We thank Anne Christophe, Isabelle Darcy, Lisa Feigenson, and Gayaneh Szenkovits for their help with this work, and Sophie Scott, Narly Golestani, and Jonas Obleser for proofreading the article. We are also grateful to Randi Martin and two anonymous reviewers for their many helpful comments on earlier versions of this paper. This work was supported by ESRC, the Fyssen Foundation, and the INSERM through an Interface grant, and an Avenir grant.

Notes

¹ This estimated span was computed by regressing the average recall rate across sequence length with a nonlinear sigmoid function. This was done in SPSS by fitting the data of each individual participant using the nonlinear model.

² We also used babble noise mask of 3,000 ms instead of 1,000 ms in order to make the AX discrimination task more difficult but patients' performance was as good as without any mask. A.T. and F.L. discriminated correctly 96% of the items.