Contrastive adaptation effects along a voice-nonvoice continuum

Adaptation to sentences and melodies when making judgments along a voice-nonvoice continuum

Adaptation to constant or repetitive sensory signals serves to improve detection of novel events in the environment and to encode incoming information more efficiently. Within the auditory modality, contrastive adaptation effects have been observed within a number of categories, including voice and musical instrument type. A recent study found contrastive perceptual shifts between voice and instrument categories following repetitive presentation of adaptors consisting of either vowels or instrument tones. The current study tested the generalizability of adaptation along a voice-instrument continuum, using more ecologically valid adaptors. Participants were presented with an adaptor followed by an ambiguous voice-instrument target, created by generating a 10-step morphed continuum between pairs of vowel and instrument sounds. Listeners' categorization of the target sounds was shifted contrastively by a spoken sentence or instrumental melody adaptor, regardless of whether the adaptor and the target shared the same speaker gender or similar pitch range (Experiment 1). However, no significant contrastive adaptation was observed when nonspeech vocalizations or nonpitched percussion sounds were used as the adaptors (Experiment 2). The results suggest that adaptation between voice and nonvoice categories does not rely on exact repetition of simple stimuli, nor does it solely reflect the result of a sound being categorized as being human or nonhuman sourced. The outcomes suggest future directions for determining the precise spectro-temporal properties of sounds that induce these voice-instrument contrastive adaptation effects.

Contrastive adaptation effects along a voice-nonvoice continuum

Adaptation to the environment is a universal property of perception across all sensory modalities. It can enhance the salience of new events in an ongoing background and helps maintain perceptual constancy in the face of variable sensory input. Several contrastive adaptation effects have been identified using sounds within the categories of human voice and musical instruments. The present study investigated whether such contrast effects can occur between voice and nonvoice stimulus categories. A 10-step continuum between "voice" (/a/, /o/, or /u/ vowels) and "instrument" (bassoon, horn, or viola) sounds was generated for each of the nine possible pairs. In each trial, an adaptor, either a voice or instrument, was played four times and was followed by a target from along the appropriate continuum. When trials with voice and instrumental adaptors were grouped into separate blocks, strong contrastive adaptation effects were observed, with the target more likely to be identified as a voice following instrumental adaptors and vice versa (Experiment 1). The effects were not observed for visual image adaptors (Experiment 2). The effects were somewhat larger when the adaptors and the target were presented to the same than to different ears, but significant adaptation was observed in both conditions, suggesting contributions of central mechanisms, following binaural integration (Experiment 3). The effect accumulated when the same type of adaptor was presented consecutively and persisted following the end of the adaptors (Experiment 4). The discovery of voice-nonvoice contrastive pairs opens the possibility of studying perceptual or neuronal voice selectivity while keeping acoustic features constant. (PsycInfo Database Record (c) 2024 APA, all rights reserved).