SIMULTANEITY IN THE TERNUS CONFIGURATION - PSYCHOPHYSICAL DATA AND A COMPUTER-MODEL

The Ternus configuration is an apparent motion display, which is typic ally described as being bistable; subjects usually describe seeing eit her element motion or group motion, depending upon temporal properties of the display. The results of an experiment are reported in which su bjects are also permitted to report seeing four stationary display ele ments (simultaneity). It was found that simultaneity was produced when both frame durations and interstimulus intervals (ISIs) were brief. A weaker than expected effect of stimulus onset asynchrony (SOA) was re vealed because this third type of judgment was obtained. Furthermore, statistical analyses indicated that SOA was not by itself the best pre dictor of judgment type. The interaction between duration and ISI was also an important predictor. This suggested that a complete account of the Ternus configuration requires two mechanisms: a visible persisten ce mechanism, governed by an SOA law, and a motion correspondence mech anism, governed by an ISI law. These two mechanisms were added to Daws on's (1991) [Psychological Review, 98, 569-603] autoassociative networ k for motion correspondence processing. The resulting model could gene rate each of the three interpretations of the Ternus configuration at appropriate combinations of frame duration and ISI.