It is widely acknowledged that a precondition for the perception of the world of objects and events is an early process of organization, and it has generally been assumed that such organization is based on the Gestalt laws of grouping. However, the stage at which such grouping occurs, whether early or late, is an empirical question. It is demonstrated in two experiments that grouping by similarity of neutral color is based not on similarity of absolute luminance at the level of the proximal stimulus, but on phenomenal similarity of lightness resulting from the achievement of lightness constancy. An alternative explanation of such grouping based on the equivalence of luminance ratios between elements and background is ruled out by appropriate control conditions.
The present experiments assessed poison-based aversion learning and retention in freely feeding and drinking domestic chicks whose drinking water was colored blue and adulterated with LiCl for a 24-hr period. The amount of LiCl self-administered by 11-day-old chicks and their subsequent avoidance of unadulterated water of the same color was examined. The results of four experiments demonstrated that chicks self-administered large and often lethal doses of the LiCl solution. Chicks subsequently avoided blue water during two-bottle preference tests administered 3 to 7 days but not 14 days after exposure. These data indicate that neophobia alone is insufficient to prevent nondeprived chicks from ingesting large quantities of a toxin during their initial encounter with it. The lack of long-term retention in the present experiments indicates that naturally occurring aversions based on visual and illness cues, while effective in the short term, may not be a major factor in the choices made by freely feeding and drinking chicks over the long term.
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