Revealing the stimulus-driven component of attention through modulations of auditory salience by timbre attributes.

Attention allows the listener to select relevant information from their environment, and disregard what is irrelevant. However, irrelevant stimuli sometimes manage to capture it and stand out from a scene because of bottom-up processes driven by salient stimuli. This attentional capture effect was observed using an implicit approach based on the additional singleton paradigm. In the auditory domain, it was shown that sound attributes such as intensity and frequency tend to capture attention during auditory search (cost to performance) for targets defined on a different dimension such as duration. In the present study, the authors examined whether a similar phenomenon occurs for attributes of timbre such as brightness (related to the spectral centroid) and roughness (related the amplitude modulation depth). More specifically, we revealed the relationship between the variations of these attributes and the magnitude of the attentional capture effect. In experiment 1, the occurrence of a brighter sound (higher spectral centroid) embedded in sequences of successive tones produced significant search costs. In experiments 2 and 3, different values of brightness and roughness confirmed that attention capture is monotonically driven by the sound features. In experiment 4, the effect was found to be symmetrical: positive or negative, the same difference in brightness had the same negative effect on performance. Experiment 5 suggested that the effect produced by the variations of the two attributes is additive. This work provides a methodology for quantifying the bottom-up component of attention and brings new insights on attention capture and auditory salience.