Date on Senior Honors Thesis

5-2022

Document Type

Senior Honors Thesis

Degree Name

B.S.

Department

Psychological and Brain Sciences

Degree Program

College of Arts and Sciences

Author's Keywords

acoustic onset edges; neural oscillatory entrainment; signal-to-noise ratio; spatial release from masking; intrinsic cues; extrinsic cues; phase locking; voice onset time

Abstract

Speech perception is a very relevant concept occurring every day. Acoustic context effects such as temporal contrast effects (TCEs) influence perception significantly. For instance, when a faster context sentence is spoken, the participant should perceive the following target word as slower and more like /t/ in “tier”; when a slower context sentence is spoken, the participant should perceive the following target sound as faster and more like /d/ in “deer”. Recent work by Bosker et al. (2020) concluded that selective attention (directing attention to a specific stimulus while ignoring surrounding stimuli) had no effect on TCEs, suggesting they were automatic and low-level. However, their paradigm was not an ideal test; the voices heard contained different talkers with one presented to each ear, making them easy to perceptually separate. Here, the paradigm was designed to eliminate talker variability (acoustic variability among talkers) by using the same male talker speaking one sentence to both ears, two sentences simultaneously to both ears (diotically) or one to each ear (dichotically). Two experiments tested these effects of presentation mode on TCEs. In each experiment, TCE magnitudes were similar across presentation modes. These results are consistent with Bosker et al.’s (2020) claims of TCEs being automatic and low-level. Potential neural mechanisms contributing to TCEs are discussed.

Lay Summary

Speech perception and auditory processing of surrounding sounds or stimuli is something humans experience daily. It is very important to understand the acoustic properties of sound and how those properties influence perception of those sounds whether it's to communicate or to simply survive in the environment. The experiments conducted for this thesis were designed to test speech perception and how the mode of presentation of sounds influence perception of specific target words. Participants were provided with stimuli presented as sentences spoken at fast or slow rates, and either combined or stand-alone. By measuring acoustic context effects, it can be determined how major or minor perception can be affected.

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