Parametric study of onset effects in lateralization

Abstract

When lateralization signals made up of trains of high‐frequency clicks (n per train), optimum usage of the information carried in each click results in binaural thresholds that decrease at the rate 1/n. However, when the interclick interval (ICI) is short, the relation between threshold and n is best described by raising n to the exponent k [where 0 ⩽ k ⩽ 1 and k = f(ICI)]. This implies that shorter ICIs produce greater dependence on information contained in the signal's onset, with k = 0 meaning that no information is derived beyond the first click in the train while k = 1 means that each click is equally effective. Based on discriminations of interaural differences of time (IDT), it will be shown that the relation between k and ICI is reasonably linear, ranging from a k of 0.0 for ICIs of 1–2 ms to k equal 1.0 for ICIs of about 11–13 ms. Interestingly, if the ICIs are made even longer, the k remains at 1.0 but the absolute performance grows worse. It is what one might expect if the internal jitter added to each sample of IDT was increased for widely spaced clicks but the observer was still able to integrate across the entire train. [Work supported by NINCDS.]