Filtering Reveals Form in Temporally Structured Displays
E.H. Adelson and H. Farid
Science, 286:2231, 1999

In a recent report [Science, 284:1165-1168, 1999], Lee and Blake asked whether the visual system could use temporal microstructure to bind image regions into unified objects, as has been proposed in some neural models. This work has already generated much excitement.

They presented two regions of dynamic texture. The elements of the target region changed in synchrony according to a random sequence, while the elements of the background region changed at independent times. Subjects were readily able to distinguish the shape of the target region. Lee and Blake posited the existence of new visual mechanisms ``exquisitely sensitive to the rich temporal structure contained in these high-order stochastic events.''

We believe the effects can be explained with well-known mechanisms. The filtering properties of early vision can convert the task into a simple static or dynamic texture discrimination problem. A sustained cell (temporal lowpass) will emphasize static texture through the mechanisms of visual persistence; a transient cell (temporal bandpass) will emphasize texture that is flickering or moving. These cues probably suffice to explain the perception of form in the experiments.

The response from Lee and Blake.