Abstract
Early experimental accounts of learning assumed that reinforcement strengthened associative bonds whereas nonreinforcement weakened them. Strengthening-weakening models explain the adjustment of nonmammalian species to downshifts in incentive magnitude, but fail to explain a mammalian phenomenon known as successive negative contrast (SNC). In SNC, exposure to incentive downshift leads to poorer performance than that of unshifted controls. SNC forced the development of new learning models emphasizing the acquisition of expectancies and the induction of emotional responses when expectancies are violated. Comparative research suggests a distinction between allocentric learning (tracking changes in the environment) and egocentric learning (remembering the emotional response to environmental changes). Recent research shows that egocentric learning in the SNC situation is modulated by the opioid system. Similar modulation is observed in situations involving physical pain, fear, and social exclusion. An evolutionary hypothesis about the evolution of egocentric learning mechanisms suggests deep connections between the brain circuits controlling fear, frustration, and possibly grief.
