Agus, T. 1, 2 & Pressnitzer, D. 1, 2
1 Laboratoire Psychologie de la Perception, UMR 8158, CNRS & U. Paris Descartes
2 Ecole normale supérieure, 29 rue d’Ulm, 75005 Paris, France
One basic goal of auditory perception is to recognize the plausible physical causes of incoming sensory information. In order to do so, listeners must learn recurring features of complex sounds and associate them with sound sources. However, how memories emerge from everyday auditory experience with arbitrary complex sounds is currently largely unknown. We will describe a novel psychophysical paradigm designed to observe the formation of new auditory memories [Agus, Thorpe, & Pressnitzer, Neuron, 2010]. The behavioral measure was based on the detection of repetitions embedded in 1s-long noises. Unbeknownst to the listeners, some noise samples re occurred randomly throughout an experimental block. In line with our hypothesis, repetitions in these re-occurring noises were detected more frequently, showing that repeated exposure could induce learning of otherwise meaningless sounds. The learning displayed several striking features: it was unsupervised and resilient to interference from other task-relevant noises. When memories where formed, they emerged rapidly, performance became abruptly near-perfect, and multiple noises were remembered for several weeks. The acoustic transformations to which recall was tolerant suggest that the learnt features were local in time and generalizable over a range of frequencies. We will also present new results: in subsequent experiments, listeners were presented learnt noises but without a within-trial repetition. They often mistakenly reported that these stimuli were repeated, suggesting that they relied to some extent on noise recognition, rather than repetition detection. Listeners were also able to learn sounds in the absence of within-trial repetitions, showing that the auditory learning mechanism could function at larger interstimulus intervals. Based on these results, we hypothesize that the ubiquitous rapid plasticity we observed could be key to the efficient formation of auditory memories. As the noise-learning paradigm uses totally meaningless sounds, it is well-suited to studying the effect of auditory learning on low-level perception.