Accurate visual memory of colors in controlling the pecking behavior of quail chicks

Animals are predisposed to memorize specific features of objects they encou nter, and to link them with behavioral outputs in a selective manner. In th is study, we examined whether chicks memorize objects by colors, and how th ey exploit the memorized color cues for selective pecking in 1- to 2-days-o ld quail chicks (Coturnix japonica). Ball-shaped beads painted in green (G) , yellowish green (YG) and the intermediate color (YGG) were used. Repetiti ve presentation of a bead (interval: 4.5 min) resulted in gradually fewer p ecks (habituation). Subsequent presentation of a different color caused pro portionately more pecks (dishabituation); e.g., after habituation to the G bead, the YG bead caused a stronger dishabituation than the YGG bead did. T he dishabituation appeared symmetric; e.g., the YG bead caused as strong di shabituation after the G-habituation, as was caused by the G bead after the YG-habituation. Number of pecks could thus reveal the memory-based color p erception in chicks. Similar discrimination of beads by memorized color cue s was found after one-trial passive avoidance training, where chicks learne d to avoid a bitter-tasting object without any differential pre-training ex periences. However, proportion of the chicks that discriminated between dif ferent colors became progressively smaller at test 15 min, 1 hr, and 24 hr post-training. On the other hand, proportion of chicks that distinguished b eads by non-color cues remained unchanged. Chicks may primarily form an acc urate memory of colors, but gradually change the link between the color mem ory and the pecking behavior.