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Robert G. Meyerson, Stephen E. Palmer; Change blindness in synchrony grouping. Journal of Vision 2004;4(8):496. doi: 10.1167/4.8.496.
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Synchrony grouping occurs when multiple elements within an array change at the same time, even if they do not change in the same way. It is a potent grouping factor, but its effect can be virtually eliminated simply by adding a brief blank frame between the frames that contain the elements, analogous to the effect of blank frames in the phenomenon of change blindness. Control conditions in which the blank frame was positioned within (rather than between) frames showed that these effects were not due simply to transients produced by the blank frames; they must be temporally aligned with the element changes. Drastic reductions in synchrony grouping can also be achieved without blanking the display, however, by changing the contrast of a square grid of lines that lie between each element and its neighbors, provided that the grid changes at the same time as the elements change. This shows that the “change blindness” effect is not due merely to the absence of element changes, but to the presence of other synchronous changes in the display. When contrast changes in the grid are reduced, however, the change blindness effect gradually diminishes. We studied these effects psychophysically by having observers discriminate between perceived vertical vs. horizontal borders induced by synchrony grouping within square arrays of elements. The results thus far are consistent with an account of synchrony grouping in terms of spatially and temporally localized change signals that occur whenever and wherever changes take place and with a strength that depends on the magnitude of the change. By this account synchrony grouping is disrupted by blanking and by changes in the contrast of the grid because they effectively mask the contrast changes in the to-be-grouped elements.
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