Abstract
Two fundamental properties of perception are selective attention and perceptual contrast, but how these two processes interact remains unknown. Does an attended stimulus history exert a larger contrastive influence on the perception of a following target than unattended stimuli? Dutch listeners categorized target sounds with a reduced prefix “ge-” marking tense (e.g., ambiguous between gegaan-gaan “gone-go”). In ‘single talker’ Experiments 1–2, participants perceived the reduced syllable (reporting gegaan) when the target was heard after a fast sentence, but not after a slow sentence (reporting gaan). In ‘selective attention’ Experiments 3–5, participants listened to two simultaneous sentences from two different talkers, followed by the same target sounds, with instructions to attend only one of the two talkers. Critically, the speech rates of attended and unattended talkers were found to equally influence target perception – even when participants could watch the attended talker speak. In fact, participants’ target perception in ‘selective attention’ Experiments 3–5 did not differ from participants who were explicitly instructed to divide their attention equally across the two talkers (Experiment 6). This suggests that contrast effects of speech rate are immune to selective attention, largely operating prior to attentional stream segregation in the auditory processing hierarchy.
Highlights
Two fundamental properties of perception are selective attention and perceptual contrast, but how these two processes interact remains unknown
In a slow context, syllables can disappear from perception[9,10]. This acoustic context effect induced by the surrounding speech rate, known as a temporal contrast effect or rate normalization, has been shown to influence a wide range of different duration-based phonological cues such as voice onset time (VOT; 11,12), formant transition duration[13], vowel duration[14,15], lexical stress[16], and word segmentation[17,18]
The categorization results (Fig. 2) demonstrate that slow context sentences resulted in fewer ‘prefix present’ responses than fast sentences, indicating that slow speech rates made the prefix in the target ‘disappear’ (p = 0.004), thereby replicating previous findings of temporal contrast effects
Summary
Two fundamental properties of perception are selective attention and perceptual contrast, but how these two processes interact remains unknown. These two fundamental processing principles are thought to play a critical role in the ability of biological systems to survive in their typically highly variable environments by allowing them to recognize meaningful items despite variability in their appearance and despite various forms of background noise[4] Both contrast enhancement and selective attention have been found to operate on a range of perceptual features such as brightness, hue, pitch, loudness, and temperature, to name a few. Whether temporal contrast effects are modulated by selective attention remains unknown It is unclear whether the speech rate of unattended stimuli does or does not induce contrastive effects on the perception of a following attended target. Acoustic context effects in general appear when listeners perform demanding concurrent tasks in the visual domain[29]
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