the effects of three levels of food deprivation, and shift in reinforcement patterns were investigated in selectively bred high-(rha/lu) and low( rla/lu) avoidance strains. the high-avoidance strain responded to the appetitive drive to a greater extent than the low-avoidance strain whereas the low-avoidance strain responded to change in reinforcement pattern more strongly than the high-avoidance strain. the males and females of both the rha/lu and rla/lu strain responded differently to the change in food deprivation pattern. the rha/lu females and the rla/lu males yielded an inverted u-shaped function over the three food deprivation levels.