Choice with Concurrent Interval Schedules of Reinforcement: The Effects of Different Timing Procedures

Using a Findley changeover procedure, two groups of rats were exposed to various concurrent variable-time (VT) schedules of milk presentation. The rules governing the operation of the timers for the stimulus events differed for the two groups with resulting differences in the overall degree of changeover responding but not with respect to time allocation measures, which in both cases consisted of undermatching. When an interrupted VT reinforcement timer was reset upon re-entry of that component, the rats tended to emit changeover responses almost exclusively to the more favorable component. When the VT reinforcement timers were left running regardless of which components the rats selected, changeover responses were significantly more frequent and equally distributed among both the more and less favorable components. In comparing the present results with those from a similar procedure in which shock was used (Deluty & Church, 1978), it is apparent that what is basic to choice in concurrent interval schedules is not matching or some mathematical variation of it. Instead, it is a tendency to optimize on the basis of the favorability of the stimulus events and the contingencies regarding how those events are timed and administered.

     

Exploring the limits of peripheral vision for the control of movement

The role played by peripheral visual information in the control of aiming movements is not fully understood, as is indicated by the conflicting results reported in the literature. In the present study, the authors tested and confirmed the hypothesis that the source of the conflict lies in the portion of the visual peripheral field that has been under scrutiny in the different studies. Participants (N = 60) moved a computer mouse from a fixed starting position to 1 of 3 targets under varied vision conditions. The portion of the peripheral visual field that best ensured directional accuracy of a sweeping movement was found to be located between 20 degrees and 10 degrees of visual angle, whereas the area found to favor directional accuracy of an aiming movement comprised 30 degrees through 10 degrees of visual angle.     

The Effect of Culture on a Visual-Spatial Memory Task

The visual-spatial memory ability of 25 Zairian elementary school children was compared with that of 23 Scottish children, using a variation of Kearins's (1976) object placement task. The Scottish children demonstrated significantly better visual-spatial memory than the Zairian children when the easiest (small household objects) of three arrays was presented. The Scottish and Zairian children demonstrated a similar level of visual-spatial ability when the other two arrays (geometric shapes and a variety of natural pieces of wood) were presented, and there were no significant gender differences. Although the Australian Aboriginal children's performance on the visual-spatial task in Drinkwater's (1976) study was superior to the White children's performance (Kearins, 1976, 1981), the Zairian children's performance in this study was not. Perhaps the Aboriginal groups, over countless generations navigating the trackless desert of western Australia, were forced by their environment to develop an aptitude for direction finding that Zairians (whose ecological situation more closely resembles that of Europeans) have not.     

The Development of Hyperactive–Impulsive Behaviors During the Preschool Years: The Predictive Validity of Parental Assessments

The objectives of this study were to establish the different developmental trajectories of hyperactive-impulsive behaviors on the basis of both mother and father ratings at 19, 32, 50, and 63 months, and to examine the predictive validity of these trajectories with respect to later hyperactive-impulsive behaviors, as rated by teachers in the first 2 years of school. Hyperactive-impulsive behaviors were assessed in a population-based sample of 1,112 twins (565 boys and 547 girls) at 19, 32, 50, and 63 months of age. The results revealed a differentiated and consistent view of developmental trajectories of hyperactive-impulsive behaviors derived from these repeated assessments, with 7.1% of children seen by mothers (7% for fathers) as displaying high and stable hyperactive-impulsive behaviors. According to mother ratings, children on a high-chronic trajectory were more likely than other children to display hyperactive-impulsive behaviors at 72 and 84 months according to their teachers. Repeated measures over time and father-based trajectories significantly added to the prediction teacher later ratings of hyperactive-impulsive behaviors. These results support the predictive validity of parental assessment of hyperactive-impulsive behaviors during the preschool years and their use to identify children at risk for further evaluation and possible intervention.     

A longitudinal twin study of the genetic and environmental etiology of maternal hostile-reactive behavior during infancy and toddlerhood

Children's negative characteristics are thought to be a factor in evoking hostile parenting responses. This can result in genotype/environment correlations (rGE) in which children's heritable traits influence the parenting they experience. We did genetic analyses on 292 mothers' self-reported hostile-reactive behaviors toward each of their twins at 5, 18 and 30 months. Finding heritability for a parenting behavior analyzed as a child phenotype is evidence of rGE correlation. The heritability of maternal behavior was modest (29% at 5 months, 0% at 18 months, and 25% at 30 months) and longitudinal analyses indicated that genetic factors at 5 and 30 months were uncorrelated. Common environment factors, probably reflecting characteristics of the mothers, were the main source of variance at the three ages and were highly correlated through time. We concluded that children's heritable characteristics evoked maternal negative response at specific times, but were not responsible for the stability of maternal hostility from infancy to toddlerhood.     

Horse (Equus caballus) whinnies: a source of social information

Many animal species that rely mainly on calls to communicate produce individual acoustic structures, but we wondered whether individuals of species better known as visual communicants, with small vocal repertoires, would also exhibit individual distinctiveness in calls. Moreover, theoretical advances concerning the evolution of social intelligence are usually based on primate species data, but relatively little is known about the social cognitive capacities of non-primate mammals. However, some non-primate species demonstrate auditory recognition of social categories and possess mental representation of their social network. Horses (Equus caballus) form stable social networks and although they display a large range of visual signals, they also use long-distance whinny calls to maintain contact. Here, we investigated the potential existence of individual acoustic signatures in whinny calls and the ability of horses to discriminate by ear individuals varying in their degree of familiarity. Our analysis of the acoustic structure of whinnies of 30 adult domestic horses (ten stallions, ten geldings, ten mares) revealed that some of the frequency and temporal parameters carried reliable information about the caller’s sex, body size and identity. However, no correlations with age were found. Playback experiments evaluated the behavioural significance of this variability. Twelve horses heard either control white noise or whinnies emitted by group members, familiar neighbours or unfamiliar horses. While control sounds did not induce any particular response, horses discriminated the social category of the callers and reacted with a sound-specific behaviour (vigilance and attraction varied with familiarity). Our results support the existence of social knowledge in horses and suggest a process of vocal coding/decoding of information.     

Associations of Maternal Prenatal Smoking with Early Childhood Physical Aggression,Hyperactivity-Impulsivity,and Their Co-Occurrence

This study investigated associations between maternal prenatal smoking and physical aggression (PA), hyperactivity-impulsivity (HI) and co-occurring PA and HI between ages 17 and 42 months in a population sample of children born in Québec (Canada) in 1997/1998 (N=1745). Trajectory model estimation showed three distinct developmental patterns for PA and four for HI. Multinomial regression analyses showed that prenatal smoking significantly predicted children’s likelihood to follow different PA trajectories beyond the effects of other perinatal factors, parental psychopathology, family functioning and parenting, and socio-economic factors. However, prenatal smoking was not a significant predictor of HI in a model with the same control variables. Further multinomial regression analyses showed that, together with gender, presence of siblings and maternal hostile reactive parenting, prenatal smoking independently predicted co-occurring high PA and high HI compared to low levels of both behaviors, to high PA alone, and to high HI alone. These results show that maternal prenatal smoking predicts multiple behavior regulation problems in early childhood.     

The role of proactive and reactive aggression in the formation and development of boys' friendships

This study tested the hypothesis that friends are more similar in proactive aggression than in reactive aggression. Interpersonal processes that may account for this similarity (i.e., selection and mutual influence) were also examined. In the fall and spring of the school year, the friendships of 185 4th-, 5th-, and 6th-grade boys were identified. Proactive and reactive aggressive behavior were assessed with a teacher-rating instrument for each boy. The results support the general hypothesis and suggest that proactively aggressive boys tend to select proactively aggressive peers as friends; however, mutual influence between stable friends does not appear to account for similarity. These findings are discussed within the framework of G. R. Patterson, J. B. Reid, and T. J. Dishion's (1992) theory of antisocial behavior.