Sources of behavioral deviation modeled by early color preferences in quail. I. Behavioral synergism and systemic instability.

Differences between population-typical norms of individual variability were studied in five genetic lines of Japanese quail (Coturnix coturnix japonica); two (BL and RL) were bidirectionally selected for early approach preference between blue and red stimuli, two (Hi and Lo) for high and low imprintabilities to the same stimuli, and the fifth (CL) was an unselected genetic control line. Selection resulted in reliably divergent extreme choice performances and imprintabilities and in progressively increasing choice variances in the BL x RL hybrids and the Hi imprintability line. Experimentation tested and rejected the hypotheses that correlated selection of synergistically acting but otherwise extraneous stimulus influences, social interaction effects, or phototactic and short-term learning effects may have been responsible for the observed large variance increases. An alternative interpretation is discussed, according to which directional selection relaxes the genetic buffering and the variance increases reflect the resulting developmental instability of the trait.