Stimulus Onsets and Offsets (Dick Pastore )

Subject: Stimulus Onsets and Offsets
From:    Dick Pastore  <pastore%bingvmb.bitnet(at)UTCS.UTORONTO.CA>
Date:    Tue, 30 Jun 1992 12:13:46 -0400

Al: I returned from vacation to find an interesting E-mail discussion on the importance of stimulus onset. We have several older studies (all published in Perception & Psychophysics) which looked at different aspects of stimulus onset and offset. In one series of studies we were interested in the possible role played by stimulus change in non-simultaneous masking. The motivation for the study was (1) the apparent salience of stimulus change in the electrophysiological encoding of sensory information, (2) the importance of spatial and temporal contours (change) in a number of different sensory systems, and (3) the increased masking of gated over continuous maskers (work of Rabb and Green). In one of our articles (P & P, 1975, 17, 445-449) we report on a potential contribution of stimulus change to backward masking. In a later study (P & P, 1980, 28, 547-549) we report on an interaction between backward and forward masking based upon both cuing and attentional properties of stimulus onsets and offsets. In our work on temporal order identification, we included an evaluation of the abruptness of stimulus onset (P & P, 1988, 44, 257-271). For stimuli with abrupt onsets (10 ms or less), temporal order identification threshold is independent of stimulus rise time. For stimuli with more gradual onsets, the temporal order identification threshold is a function of stimulus rise time, thus paralleling findings reported for speech stimuli. Finally, we also have looked at temporal order identification for stimulus offset (P & P, 1983, 33, 54-62). I hope that some of this information is useful to you and others interested in the perceptual organization of stimuli. I look forward to the continuing dialogue on this topic. Dick Pastore

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Electrical Engineering Dept., Columbia University