N-Methyl-D-aspartate receptors (NMDARs) mediate certain forms of synaptic plasticity and learning. We used a touchscreen system to assess NR2A subunit knockout mice (KO) for (1) pairwise visual discrimination and reversal learning and (2) acquisition and extinction of an instrumental response requiring no pairwise discrimination. NR2A KO mice…

Small deviations from bilateral symmetry (fluctuating asymmetries) are cues to fitness differences in some animals. Therefore, researchers have considered whether animals use these small asymmetries as visual cues to determine appropriate behavioral responses (e.g., mate preferences). However, there have been few systematic studies of animals'…

Two normal and two mentally retarded children were trained to earn pennies by pressing a key according to a multiple variable-interval extinction schedule of reinforcement. Retarded children differed from normal children by producing more positive than negative discriminative stimuli. (Author/DB)

Experiment 1 supported in part by National Institute of Mental Health (NIMH) Research Grant M2232. Experiment 2 submitted as the senior author's PhD dissertation at the University of Miami and supported by NIMH grant MH-14914.