Abstract

The ability to detect sudden changes in the environment is critical for survival. Hearing is hypothesized to play a major role in this process by serving as an “early warning device,” rapidly directing attention to new events. Here, we investigate listeners' sensitivity to changes in complex acoustic scenes—what makes certain events “pop-out” and grab attention while others remain unnoticed? We use artificial “scenes” populated by multiple pure-tone components, each with a unique frequency and amplitude modulation rate. Importantly, these scenes lack semantic attributes, which may have confounded previous studies, thus allowing us to probe low-level processes involved in auditory change perception. Our results reveal a striking difference between “appear” and “disappear” events. Listeners are remarkably tuned to object appearance: change detection and identification performance are at ceiling; response times are short, with little effect of scene-size, suggesting a pop-out process. In contrast, listeners have difficulty detecting disappearing objects, even in small scenes: performance rapidly deteriorates with growing scene-size; response times are slow, and even when change is detected, the changed component is rarely successfully identified. We also measured change detection performance when a noise or silent gap was inserted at the time of change or when the scene was interrupted by a distractor that occurred at the time of change but did not mask any scene elements. Gaps adversely affected the processing of item appearance but not disappearance. However, distractors reduced both appearance and disappearance detection. Together, our results suggest a role for neural adaptation and sensitivity to transients in the process of auditory change detection, similar to what has been demonstrated for visual change detection. Importantly, listeners consistently performed better for item addition (relative to deletion) across all scene interruptions used, suggesting a robust perceptual representation of item appearance.

Highlights

  • The ability to detect and quickly respond to new events in the environment is critical to an organism’s struggle for survival

  • There is a remarkable difference in performance for CA versus CD stimuli: while subjects remained at ceiling performance for CA stimuli for all scene sizes, there was a sharp decrease in CD hit rates as scenes became more populated (Figure 3A)

  • To examine the interaction, repeated measures ANOVA demonstrated an effect of scene size for both CA (F(1.994,11.964) = 11.03; p = 0.002) and CD (F(1.836,11.014) = 14.88; p = 0.001) stimuli, with the observed interaction indicating a sharper slope in the case of CD trials

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Summary

Introduction

The ability to detect and quickly respond to new events in the environment is critical to an organism’s struggle for survival. Accumulating evidence has demonstrated that the visual system is highly sensitive to local transients (rapid changes in luminance/colour in a small section of the retinal image) such as would be generated by the abrupt appearance, disappearance or movement of objects within the scene. These events automatically draw attention towards the locations where they occur [3] resulting in perceptual ‘pop-out’ of the changing element. The auditory system is commonly assumed to play a key role in the brain’s changedetection network by serving as an ‘early warning device’, rapidly directing attention to new events in the scene [7,8]

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