Brightness effects on color pecking preferences in dark-hatched domestic chicks

Color pecking preferences in day-old, dark-hatched domestic chicks of 2 breeds were studied as a function of (1) target luminance (dim, medium, or bright) when testing was in darkness and in the light (Experiments I and II): (2) method of equilibrating target brightnesses (i.e., objectively or subjectively: Experiments III and IV); and (3) ambient brightness (dim, medium, or bright; Experiment IV). White Leghorns were found to peck sooner and more often than New Hampshires. Under all conditions of target and ambient brightness, results revealed the previously reported bimodal (V-shaped) color preference function with peak preferences in the blue-violet and orange regions of the spectrum and minimal at green. The only brightness factor that affected the V-shaped function was dark-adapted vs light-adapted viewing, that is, the chicks showed a slight shift away from red and/or a slightly more negative slope with light adaptation.