Cite as:
Chukova S V, Kaiander I N, Ahumada A J Jr, 2001, "Is apparent motion real or really apparent?" Perception 30 ECVP Abstract Supplement

Is apparent motion real or really apparent?

S V Chukova, I N Kaiander, A J Ahumada Jr

Discrimination thresholds for separation between two vertical lines presented with a short delay are much lower than for those presented with a long delay (Chukova and Gauzelman, 1997 Perception 26 Supplement, 115 - 116). At short interstimulus intervals (ISIs) (0.05 - 0.2 s), all observers report the stimuli to be 'moving'; however, this perception disappears at the 2 s ISI. To look for possible effects of apparent motion, we hypothesised different thresholds for 'moving away' (reference wider than comparison, R > T) and 'approaching' (R < T) stimuli. If the apparent motion affects discrimination, then at short ISIs the number of correct responses for R > T and R < T might differ. Furthermore, if the apparent motion does improve discrimination, the improvement should occur whichever method is used for measuring threshold [classical method of constant stimuli (MCS), using a single reference, or modified MCS, using mixed references]. For classical MCS, at short ISIs (0.05 and 0.2 s), regression analysis shows no difference between the correct responses for 'moving away' and 'approaching' in 75% of the cases. In contrast, for long ISI (2 s), the difference is highly significant (p < 0.05 in 75% cases). For modified MCS, the difference between 'moving away' and 'approaching' is significant in 88% of the cases, independent of ISI. The results suggest that the apparent motion has no obvious effect on size discrimination, suggesting rather that the retrieval processes might be more important determinants of discrimination performance.[Supported by Russian Foundation for

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