Enhancement of pigeons’ conditional discrimination performance by expectancies of reinforcement and nonreinforcement

Prior work has shown that when the separate correct responses of a conditional discrimination are followed by different reinforcing outcomes, performance is enhanced relative to that obtained under the conventional, single-reinforcer procedure. Four experiments with pigeons yielded the analogous finding when the different outcomes were reinforcement and explicit nonreinforcement. Controls indicated that the results could not be attributed to the effects of intermittent reinforcement, to possible differences in cue duration, or to a variety of potential sources of conditioned reinforcement. An interpretation in terms of expectancy learning is proposed.     

Deviant Peer Factors During Early Adolescence: Cause or Consequence of Physical Aggression?

This study investigated reciprocal relations between adolescents' physical aggression and their perceptions of peers' deviant behaviors and attitudes. Analyses were conducted on four waves of data from 2,290 adolescents (ages 10–16) from three urban middle schools. Autoregression models revealed reciprocal relations between peer factors (i.e., friends' problem behavior, peer pressure for fighting, friends' support for fighting) and adolescents' reporting of their aggressive behavior. Bidirectional relations were also found between peer pressure for fighting and adolescents' frequency of physical aggression based on teacher ratings. Findings were consistent across sex, grade, and time. Findings suggest that multiple dimensions of peers' behaviors uniquely play a role in the development of adolescents' aggression and have important implications for interventions to reduce problem behaviors.