There is an ability to map acoustic stimuli to phonetic categories when based on timing differences in voiced information, both early and late in schizophrenia, a new study suggests. Researchers measured categorical processing of artificial syllables that varied in voice-onset time (VOT), and how sensory biasing impacts categorical perception. Participants chose whether a syllable sounded more like /ba/ or /pa/. 22 individuals with long-term schizophrenia (Sz) were compared to 21 controls (HCSz), and 17 individuals at their first-episode of schizophrenia (FE) were compared to 19 controls (HCFE). Among the findings:
- All groups showed categorial perception and category shifts during biased conditions.
- Sz and FE were statistically indistinguishable from controls in the point of categorical shift, slope of their response function, and the VOT needed to reliably perceive /pa/.
Haigh SM, Laher RM, Murphy TK, et al. Normal categorical perception to syllable-like stimuli in long term and in first episode schizophrenia. [Published online ahead of print April 11, 2019]. Schizophr Res. doi:10.1016/j.schres.2019.03.028.