mirror neuron systems became activated as the primate learned to use the hammer to crack nuts. However, when the primate was not presented with a social learning opportunity, the mirror neuron systems did not activate and learning did not occur. Similar studies with humans also show similar evidence to the human mirror neuron system activating when observing another person perform a physical task. The activation of the mirror neuron system is thought to be critical for the understanding of goal directed behaviors and understanding their intention. Although still controversial, this provides a direct neurological link to understanding social cognition. Applications Criminology Social learning theory has been used to explain the emergence and maintenance of deviant behavior, especially aggression. Criminologists Ronald Akers and Robert Burgess integrated the principles of social learning theory and operant conditioning with Edwin Sutherland's differential association theory to create a comprehensive theory of criminal behavior. Burgess and Akers emphasized that criminal behavior is learned in both social and nonsocial situations through combinations of direct reinforcement, vicarious reinforcement, explicit instruction, and observation. Both the probability of being exposed to certain behaviors and the nature of the reinforcement are dependent on group norms. Developmental psychology In her book Theories of Developmental Psychology, Patricia H. Miller lists both moral development and gender-role development as important areas of research within social learning theory. Social learning theorists emphasize observable behavior regarding the acquisition of these two skills. For gender-role development, the same-sex parent provides only one of many models from which the individual learns gender-roles. Social learning theory also emphasizes the variable nature of moral development due to the changing social circumstances of each decision: "The particular factors the child thinks are important vary from situation to situation, depending on variables such as which situational factors are operating, which causes are most salient, and what the child processes cognitively. Moral judgments involve a complex process of considering and weighing various criteria in a given social situation." For social learning theory, gender development has to do with the interactions of numerous social factors, involving all the interactions the individual encounters. For social learning theory, biological factors are important but take a back seat to the importance of learned, observable behavior. Because of the highly gendered society in which an individual might develop, individuals begin to distinguish people by gender even as infants. Bandura's account of gender allows for more than cognitive factors in