There is evidence that one group is associated with assimilation among its parts and an increase in visibility (IV) of at least one of its parts: the 1 group-assimilation-IV position. The present research supports this position using physically identical stimuli, hence eliminating differences in features. This was accomplished by comparing the effects of large and small backgrounds on responding to physically identical stimuli that appeared on these backgrounds. Compared to the small background, the large background produced a stronger two-line group according to a closure measure of grouping, more assimilation between two lines according to a same-different measure of perceived similarity, and a greater IV of one of two lines according to context+target versus context relative to target versus background discriminations. The large background was much larger than the two small lines, suggesting that it functioned as an anchor.