Choice of extinction-signalling stimuli by rats

Rats in a two-lever situation were exposed to alternating periods of intermittent reinforcement and extinction. Extinction periods were either unsignalled or were signalled by a response-produced stimulus. The signal was sometimes a stimulus paired with food delivery in the reinforcement periods and sometimes a stimulus that occurred only in extinction periods. Both kinds of signal accelerated extinction relative to the unsignalled condition. When the signal was the stimulus paired with food in reinforcement periods, the rats tended to prefer the lever that gave that signal even though the signal accelerated extinction. There was no comparable effect for the stimulus that occurred only in extinction periods; when this signal was contingent on only one of the two levers, the rats either avoided it (Experiment 3) or were indifferent (Experiment 4). It is concluded that a stimulus can be a “secondary reinforcer” as measured by preference, even though it decreases resistance to extinction; the implications are discussed with reference to formal theories of choice behavior.     

Operants

The definition of an operant as a response class each of whose members possesses the property upon which reinforcement is contingent is not broad enough to cover the units that are supposed in Skinner's accounts of extinction, superstition, and transfer of learning. A broader definition is suggested. Finally, properties defining operants are discussed.     

THE EFFECT OF SPACED VS. MASSED PRESENTATION OF AGGRESSION ITEMS ON VERBAL AGGRESSIVE RESPONSES OF CHILDREN

A story completion test was constructed and administered to 99 ten-year-old boys. The main results were: (1) The average number of aggressive responses tends to be lower when the aggression items are presented in a 'spaced' manner than when they are 'massed'. (2) There is a spread effect from aggression items to neutral items. Aggression and neutral items presented in mixed order give a stronger effect. (3) A relatively consistent factor structure of aggression responses was shown in the test. Aggression towards peers and authority were independent of each other, and seem to be influenced differently by the manner of presentation of stimuli.     

Innovations in Assessing ADHD: Development, Psychometric Properties, and Factor Structure of the ADHD Symptoms Rating Scale (ADHD-SRS)

This research involved the development of a behavior rating scale designed to measure ADHD and the investigation of the scale's psychometric properties and factor structure. This scale, the ADHD Symptoms Rating Scale (ADHD-SRS), was developed for the assessment of ADHD in the school-age (K–12) population. Participants were 1006 children and adolescents (in grades K–12) who were rated by their parents and/or teachers. The results indicate that the ADHD-SRS possesses strong internal consistency reliability and test–retest reliability and moderate cross-informant reliability. The data also suggest that the ADHD-SRS has strong content validity. Convergent validity of this instrument was also high, as demonstrated by correlations with three previously validated behavior rating scales. Significant age and gender differences in ADHD symptoms were found with both the parent and teacher respondent populations. Finally, the factor analysis of the ADHD-SRS suggested a two factor oblique rotation as the best fit for both the parent and the teacher data. After a visual inspection of the items which loaded on each factor, Factor 1 was named Hyperactive-Impulsive and Factor 2 was named Inattention. These two factors, along with the items which loaded on each factor, appear to be remarkably similar to the two categories listed in the DSM-IV for ADHD. Directions for future research, as well as clinical implications and limitations of the research are discussed.     

Categorization of natural movements by pigeons: visual concept discrimination and biological motion

In three experiments, pigeons were exposed to a discriminated autoshaping procedure in which categories of moving stimuli, presented on videotape, were differentially associated with reinforcement. All stimuli depicted pigeons making defined responses. In Experiment 1, one category consisted of several different scenes of pecking and the other consisted of scenes of walking, flying, head movements, or standing still. Four of the 4 birds for which pecking scenes were positive stimuli discriminated successfully, whereas only 1 of the 4 for which pecking was the negative category did so. In the pecking-positive group, there were differences between the pecking rates in the presence of the four negative actions, and these differences were consistent across subjects. In Experiment 2, only the categories of walking and pecking were used; some but not all birds learned this discrimination, whichever category was positive, and these birds showed some transfer to new stimuli in which the same movements were represented only by a small number of point lights (Johansson's “biological motion” displays). In Experiment 3, discriminations between pecking and walking movement categories using point-light displays were trained. Four of the 8 birds discriminated successfully, but transfer to fully detailed displays could not be demonstrated. Pseudoconcept control groups, in which scenes from the same categories of motion were used in both the positive and negative stimulus sets, were used in Experiments 1 and 3. None of the 8 pigeons trained under these conditions showed discriminative responding. The results suggest that pigeons can respond differentially to moving stimuli on the basis of movement cues alone.     

Perception of object unity in chicks: A comparison with the human infant

Newly hatched chicks (Gallus gallus) were imprinted on a display consisting of two rod pieces that moved above and below a central occluder. On test trials, the chicks approached a complete rod in preference to two rod pieces. This finding, supported by those from control coditions, suggests that chicks, soon after hatching, perceive object unity. The results are compared with those from human infants.     

Long-term stability in the Big Five personality traits in adulthood

This study investigated the stability of the Big Five personality traits in adulthood from age 33 to 42. Participants (89 men, 103 women) were drawn from the ongoing Jyväskylä Longitudinal Study of Personality and Social Development. The results showed that the mean‐level of Neuroticism decreased whereas the mean‐level of Extraversion, Openness to Experience, Agreeableness, and Conscientiousness increased from age 33 to 42. The Structural Equation Modeling analyses revealed both gender differences and similarities in the rank‐order stability of the Big Five: Neuroticism and Extraversion were more stable in men than in women, whereas Openness to Experience, Agreeableness, and Conscientiousness were as stable in men as in women. Stability coefficients for the Big Five personality traits across 9 years were moderate to high, ranging from 0.73 to 0.97 in men and from 0.65 to 0.95 in women. The highest gender‐equal stability was found for Openness to Experience and the lowest for Conscientiousness.     

Parental monitoring moderates the importance of genetic and environmental influences on adolescent smoking

Although there is a substantial literature on the role of parenting in adolescent substance use, most parenting effects have been small in magnitude and studied outside the context of genetically informative designs, raising debate and controversy about the influence that parents have on their children (D. C. Rowe, 1994). Using a genetically informative twin-family design, the authors studied the role of parental monitoring on adolescent smoking at age 14. Although monitoring had only small main effects, consistent with the literature, there were dramatic moderation effects associated with parental monitoring: At high levels of parental monitoring, environmental influences were predominant in the etiology of adolescent smoking, but at low levels of parental monitoring, genetic influences assumed far greater importance. These analyses demonstrate that the etiology of adolescent smoking varies dramatically as a function of parenting.