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.     

Functional structure in sentences: A performance analysis

Two experiments are reported which attempt to define the groupings of component words within sentences which subjects have committed to memory. The structural groupings are indexed by judgement latencies for pairs of words and these serve as the input matrix for a hierarchical clustering (HC) analysis. It is concluded that when subjects make judgements concerning the forward order of pairs of words, the latencies imply the presence of a hierarchical organization. Although the tree structures obtained do not follow in any detail the surface structures of the sentence types in either experiment, nonetheless when constituent analysis indicates no difference it is accompanied by identical performance structures, and when a surface distinction is called for, an appropriate difference is found in the tree diagrams produced by cluster analysis. Deep structure differences involving the rearrangement of component words are not found in the hierarchical structure subjects imposed. The pausing patterns followed by subjects when reading the sentences are shown to relate to the structural diagrams generated by the HC analysis.     

Aftereffect of inspection of a perspectival stimulus for slant depth: A new normalization effect

The Ss made judgments of the frontoparallel plane monocularly and binocularly by adjusting the position of a rotatable thin luminous line viewed in darkness. The judgments were made before and after a 10-min period of monocular inspection of a luminous outline frontoparallel trapezoid which was the projection of a rectangle rotated in depth. Verbal reports indicated normalization of perspectival slant depth, i.e., the inspection figure appeared less rotated, and the line settings exhibited an aftereffect bf normalization. These findings may contribute toward an account of certain previously unexplained observations reported in an earlier study by Epstein and Morgan-Paap (1974) dealing with adaptation to uniocular image magnification.