The association of assimilation and an increase in visibility in perceptual grouping.

Subjects performed a series of forced-choice discriminations to determine whether both group-assimilation and group-visibility associations could be obtained from nearly identical strong and weak group patterns. The discrimination between the context+target square and the context [symbol: see text] was better than between the target- and background, as was the case for --, whose context and target components were its left and right halves, but not for [symbol: see text]. Square and -- produced a better performance when their lines (halves) were the same in color, and a poorer performance when their lines were different in color, but [symbol: see text] produced the reverse. Likewise, only square and -- produced a better performance when closed, and a poorer performance when open. These context+target etc., same-different, and closure results argue that square and -- produced a greater increase in visibility of their component --, more assimilation among their parts, and a stronger group than did [symbol: see text]. This evidence of a group-assimilation-visibility association cannot be attributed to the fortuitous occurrence of an increase in visibility with one object, assimilation with a second, and closure with a third, unlike previous evidence. This association cannot be explained by feature-based theories. Therefore, a superordinate unit is the cause of this association.