Perceptual learning for speech: Is there a return to normal?

Recent work on perceptual learning shows that listeners' phonemic representations dynamically adjust to reflect the speech they hear (Norris, McQueen, & Cutler, 2003). We investigate how the perceptual system makes such adjustments, and what (if anything) causes the representations to return to their pre-perceptual learning settings. Listeners are exposed to a speaker whose pronunciation of a particular sound (either /s/ or /integral/) is ambiguous (e.g., halfway between /s/ and /integral/). After exposure, participants are tested for perceptual learning on two continua that range from /s/ to /integral/, one in the Same voice they heard during exposure, and one in a Different voice. To assess how representations revert to their prior settings, half of Experiment 1's participants were tested immediately after exposure; the other half performed a 25-min silent intervening task. The perceptual learning effect was actually larger after such a delay, indicating that simply allowing time to pass does not cause learning to fade. The remaining experiments investigate different ways that the system might unlearn a person's pronunciations: listeners hear the Same or a Different speaker for 25 min with either: no relevant (i.e., 'good') /s/ or /integral/ input (Experiment 2), one of the relevant inputs (Experiment 3), or both relevant inputs (Experiment 4). The results support a view of phonemic representations as dynamic and flexible, and suggest that they interact with both higher- (e.g., lexical) and lower-level (e.g., acoustic) information in important ways.     

The duration component of the stress effect in stuttering

The purpose of the present study was to investigate whether there is a relationship between stuttering on stressed syllables and the duration of these syllables. Sixteen adults who stutter read a text consisting of 226 syllables. The relative stress of each syllable was rated, and syllables were categorized into long- and short-stressed syllables, unstressed syllables and intermediate syllables lying in-between. In order to isolate effects caused by within-word position from those caused by linguistic stress, syllables in initial and in subsequent positions were analyzed separately. In both word position categories stressed syllables were stuttered more often than unstressed syllables. Stuttering frequency of intermediate syllables seems to be in-between stressed and unstressed syllables, just as their stress level is rated in-between. Results regarding the duration of stressed syllables do not allow final conclusions.

Educational objectives: The reader will learn about and be able to describe (1) language factors related with stuttering events, (2) the stress effect in adults who stutter, and (3) methods to control for its confounding variables.     

When repeating aloud enhances episodic memory for spoken words: interactions between production- and perception-derived variability

We demonstrate that the phonetic detail of an original speaker’s pronunciation for a word can be detected with a memory measure even when a participant listens to and then repeats that word aloud (production). At study, native English participants heard English words pronounced by a native speaker of American-English or by a Chinese national. For half of the words they listened. For the others, they produced it. In both recall and old/new recognition tests in Experiment 1, production improved performance relative to listening alone. Effects of accent were present only in recognition and only in interaction with production. In Experiment 2, a source-monitoring recognition test where participants identified whether the speaker of a word changed from study to test, effects of accent and production were additive indicating that hearing an unfamiliar accent increased memory irrespective of production. An exemplar account including both production- as well as perception-derived experience describes the outcome.     

Exposing Individuals to Foreign Accent Increases their Trust in What Nonnative Speakers Say

People are more likely to believe things that are easier to process. Foreign-accented speech is relatively difficult to process, and prior research shows that, correspondingly, people believe information less when it is delivered in a foreign accent rather than a native accent. Here we show that a short exposure to foreign accent can reduce this bias, and that the reduction in bias is due to improvement in the processing of the accent. These results demonstrate how cognitive aspects of language processing can influence attitudes. The results also suggest that ensuring exposure to foreign accent can reduce discrimination against nonnative speakers.