A Comparison of Cues for Auditory Motion Judgments Raymond M. Stanley1,2 & Nestor Matthews1 Department of Psychology, Denison University, Granville OH 43023 USA1 Department of Psychology, Georgia Institute of Technology, Atlanta GA 30332 USA2 Purpose Results Discussion In principle, a listener could discriminate and identify the speeds of moving sounds without being sensitive to auditory motion, per se. This is because non-motion cues, such as amplitude modulation and positional information, co-vary with speed. Here we investigated the extent to which people can use these non-motion cues when judging auditory-motion stimuli. Exp 1: The Effect of Monaural, Diotic & Dichotic Stimulation The data from Exp 1 indicate that discriminability based on IID’s significantly exceeded discriminability based on amplitude modulation. This finding occurred even though, in principle, either cue was sufficient for discrimination. One possible explanation for this finding is that the neuronal response to amplitude modulation is more variable than the neuronal response to IID-defined motion. The data from Exp 2 indicate that the precision with which participants used IIDs depended significantly on motion coherence. This behavioral finding is consistent with recent single-cell recordings from the cortices of awake, rhesus monkeys; Stimulus position alone was not sufficient to predict single-cell firing rates -the sequence of positions over time was required (Malone, Scott & Semple, 2002). Relatedly, when listeners are misinformed about the sequence of IID-defined positions, auditory motion detection is significantly impaired (Stanley & Matthews, 2003). Finally, the significant position-by-direction interaction in Exp 2 suggests that we may be better at differencing the end-points of two trajectories (same direction, certain S.P. condition), than at differencing the starting and ending trajectory points (uncertain or opposite direction, certain S.P. condition). Physically, the slopes of the ‘ramps’ and ‘damps’ were the same across the 3 conditions. Motion discrimination depended significantly on stimulus condition: Monaural < Diotic < Dichotic. Method On each trial, 2 tones (500 Hz, 500 ms) were sequentially presented. Exp 1 - The first tone was always amplitude modulated, and was presented monaurally, diotically, or dichotically, randomly across trials (schematized below). The second tone was either the same as the first, or contained no amplitude modulation. On each trial, participants judged the tones to be the “same” or “different”. Exp 2: The Effect of Motion Coherence, Positional Certainty & Directional Certainty (Left) The precision of the judgments depended significantly on coherence & starting-position certainty: Scrambled < Uncertain S.P. < Certain S.P.. References (Right) There was a significant interaction between starting-position certainty & direction of motion: Opposite Dir < Same Dir, only when S.P. was certain. Malone, Scott & Semple (2002). Journal of Neuroscience, 22(11), 4625-4638. Stanley & Matthews (2003) Perception, 32(6), 731-740. Exp 2 - Participants judged whether the second tone moved “faster” or “slower” than the first, while the IID-defined positions in the stimuli changed contiguously or randomly. Also, when the positions changed contiguously, we systematically manipulated the certainty of the starting position, and the relative direction of motion (same versus opposite). This poster can be viewed and downloaded at http://denison.edu/~matthewsn/audtiorymotioncuescns2004.html