Toxicosis affects instrumental behaviour in rats

Three experiments examined the effect of toxicosis on instrumental responding. These studies were prompted by Morrison and Collyer's (1974, Experiment 1) finding that the induction of toxicosis after an instrumental conditioning session produces greater response suppression if the response is reinforced by a novel saccharin solution rather than familiar water during conditioning. Experiments 1 and 2 investigated whether this suppression was mediated by the Pavlovian contingency between the contextual cues and the saccharin solution or the instrumental relationship between the response and the reward. A role for the instrumental contingency was indicated by the greater suppression of the response producing novel saccharin rather than water when the context of both responses was equally associated with the saccharin and illness. Experiment 3 found that extinction of the aversion to a novel reinforcer following aversive conditioning would re-establish an action previously associated with that reinforcer, in contrast to an action whose reinforcer remained aversive. This result was a further indication that the instrumental contingency between the response and reward contributes to response suppression.     

Thoughts of Death and Suicide in Early Adolescence

The prevalence and persistence of thoughts of death and suicide during early adolescence were estimated in a community‐based cohort. A latent class approach was used to identify distinct subgroups based on endorsements to depression items administered repeatedly over 24 months. Two classes emerged, with 75% in a low ideation class across four assessments. Less than 2% persisted in the high ideation class over three or more assessments. African American and Asian American adolescents were more likely than European Americans to belong to the high ideation class. No members of the low ideation class endorsed “thought about killing myself,” while “thoughts of death and dying” was endorsed by members of both classes. Implications for interpreting meanings of death and suicide ideation in early adolescence are discussed.     

Intelligence, Callous-Unemotional Traits, and Antisocial Behavior

Research has consistently shown that children with severe conduct problems often exhibit intellectual deficits, especially in their verbal abilities. We investigated whether or not this finding only applies to certain subgroups of children with severe conduct problems. In a sample of 117 clinic-referred children between the ages of 6 and 13, we assessed for Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD) symptoms using a structured diagnostic interview with each child's parent and teacher, callous and unemotional traits using parent and teacher ratings, and intellectual functioning using a standard individually administered intelligence test. Children with an ODD or CD diagnosis who did not show callous and unemotional traits showed a deficit on subtests measuring verbal reasoning ability relative to a clinic control group. Children with an ODD or CD diagnosis who also showed callous and unemotional traits did not show a verbal deficit and, in fact, showed a trend toward having weaker nonverbal abilities. These results highlight the importance of recognizing distinct subgroups of children with severe conduct problems when studying potential intellectual deficits in these children.     

Listener: A tool for client-side investigation of hypermedia navigation behavior

Behavioral researchers have employed hypermedia-based software applications in their experiments for some time. More recently, interest in the World-Wide Web has developed among researchers in the social sciences, and popular use of this new medium continues to grow at an incredible rate. This paper describes Listener, a tool developed to log users’ hypermedia and World-Wide Web navigation behavior using Apple Macintosh computers in a laboratory setting. Listener is able to capture navigation actions through cached documents, overcoming some of the problems associated with analyzing standard web server logs.     

Neuropsychological performance and suicidal behavior in adult psychiatric inpatients.

Although various studies have shown that suicidal persons exhibit greater cognitive deficiencies than both normals and other psychiatric patients, researchers as yet have been unable to account for the source(s) of the differences. Some of these differences (e.g., cognitive rigidity and impaired problem solving) hint of possible organic involvement. This study explored the relationship of neuropsychological functioning to suicidal behavior by comparing 20 suicidal and 27 nonsuicidal psychiatric inpatients on several tests of neuropsychological functioning. Although results showed no significant differences between the two groups on most measures, both groups showed evidence of notably high levels of cortical dysfunction relative to test norms. Thirty-five percent of suicidal patients and 44% of nonsuicidal patients scored in the impaired range. Implications of this high frequency of impairment for the treatment of suicidal and nonsuicidal psychiatric patients are discussed.