MONAURAL PHASE DISCRIMINATION BY MACAQUE MONKEYS - USE OF MULTIPLE CUES

Research examining the discrimination of monaural phase change has sug gested that temporal envelope shape, which varies with phase, may be a n important cue. Much of that research employed stimuli consisting of three components, a center frequency (F-c,), which is varied in phase, and an upper and lower sideband separated from the carrier by some fr equency (Delta F). As the phase of the center component is varied, bot h temporal envelope and temporal fine structure change. The present re search explored the salience of both envelope and fine structure as cu es in a phase discrimination task. Monkeys were trained to report dete ction of a change from a three-tone complex with 90 degrees starting p hase for the center component to one in which the starting phase was s maller. In general, for the values of F-c, tested, thresholds for phas e change decreased as Delta F increased. When tested with comparison s timuli that had a temporal envelope closely matched to that of the sta ndard, but 0 degrees starting phase, subjects had difficulty discrimin ating these stimuli from the standard for smaller Delta F, but readily discriminated them at larger Delta F values. These findings suggest t hat temporal envelope is a critical cue in discrimination of three-ton e complexes on the basis of the starting phase of the center component at small values of Delta F, but that other cues are used at larger De lta F values. (C) 1998 Acoustical Society of America.