Date on Master's Thesis/Doctoral Dissertation


Document Type

Doctoral Dissertation

Degree Name

Ph. D.


Psychological and Brain Sciences

Degree Program

Experimental Psychology, PhD

Committee Chair

Stilp, Christian

Committee Co-Chair (if applicable)

Cashon, Cara

Committee Member

Cashon, Cara

Committee Member

DeMarco, Paul

Committee Member

Miller, Sharon

Committee Member

Zahorik, Pavel

Author's Keywords

speech acoustic; context effects; speech perception; spectral contrast; talker normalization


Speech perception is influenced by context. This influence can help to alleviate issues that arise from the extreme acoustic variability of speech. Two examples of contextual influences are talker normalization and spectral contrast effects (SCEs). Talker normalization occurs when listeners hear different talkers causing speech perception to be slower and less accurate. SCEs occur when spectral characteristics change from context sentences to target vowels and speech perception is biased by that change. It has been demonstrated that SCEs are restrained when contexts are spoken by different talkers (Assgari & Stilp, 2015). However, what about hearing different talkers restrains these effects was not entirely clear. In addition, while these are both considered contextual influences on speech perception, they have never been formally related to each other. The series of studies reported here served two purposes. First, these studies sought to establish why hearing different talkers restrained SCEs. Results indicate that variability in pitch (as measured by fundamental frequency), a primary acoustic cue to talker changes, restricts the influence of spectral changes on speech perception. Second, these studies attempted to relate talker normalization and SCEs by measuring them concurrently. Talker normalization (as measured by response times) and SCEs were evident in the same task suggesting that they act on speech perception at the same time. Further, these measures of talker normalization were shown to be influenced by f0 variability suggesting that SCEs and talker normalization are both related to f0 variability. However, no relationship between individual’s SCEs and response times was found. Possible reasons why f0 variability may restrain context effects are discussed.