Preference for less segmented fixed-time components in concurrent-chain schedules of reinforcement

A concurrent-chain procedure was used to examine choice between segmented and less segmented response-independent schedules of reinforcement. A pair of independent, concurrent variable-interval 60-s schedules were presented in the initial link, along with a 1.5-s changeover delay. A chained fixed-interval fixed-time and its corresponding tandem schedule constituted the terminal links. The length of the fixed-interval schedule in the terminal link was varied between 5 s and 30 s while that of the fixed-time schedule was kept at 5 s over conditions. The first components of both terminal-link schedules were accompanied by the same stimulus. Except in the baseline condition, the onset of the second component of the terminal-link chained schedule was accompanied by either a localized (key color) or a nonlocalized (dark houselight) stimulus change. Stimulus conditions were constant during the terminal-link tandem schedule. With three exceptions, pigeons demonstrated a slight preference for the tandem over the chained schedule in the terminal link. Furthermore, this preference varied inversely with the length of the first component. In general, these results are consistent with previous studies that reported an adverse effect on choice by segmenting an interval schedule into two or more components, but they are inconsistent with studies that reported preference for signaled over unsignaled delay of reinforcement.     

Effects of surface texture on weight perception when lifting objects with a precision grip

In this paper, we show that, when lifting an object using a precision grip with the distal pads of the thumb and index finger at its sides, the perceived weight depends on the object’s surface texture. The smoother the surface texture, the greater the perceived weight. We suggest that a smoother object is judged to be heavier because the grip force, normal to the surface, required to prevent it from slipping is greater. The possibility of there being an influence of surface texture per se is excluded by a second experiment that employed a variant of the precision grip in which the thumb supports the weight of the object from underneath. With the grip oriented in this way, there is no need to match grip force to surface texture and, under these conditions, there is no effect of surface texture on weight perception. In the first two experiments, the test and comparison weights were lifted successively by the same hand. In a third experiment, the effect of surface texture was replicated for sequential lifts made with separate hands. Thus, the effect is not restricted to comparisons made with the same hand.     

Effects of household sex composition on the salience of one's gender in the spontaneous self-concept

It was hypothesized that being a boy or a girl becomes more salient in a child's self-concept to the extent the other sex numerically predominates in the child's household. This prediction was based upon an information-processing, distinctiveness postulate that a person contemplating a complex stimulus (such as the self) selectively notices and encodes its more distinctive, information-rich aspects. The spontaneous self-concept elicited by nondirective “Tell us about yourself” interviews of 560 school children were scored for spontaneous mention of one's gender. As predicted, boys spontaneously mentioned their maleness more often when they came from households where females were in the majority; girls mentioned their femaleness more often when from households with male majorities; boys mentioned their maleness more often when from father-absent than from father-present homes. Incidental findings are that gender is more salient in the negation self-concept (“Tell us what you are not”) than in the affirmation self-concept (“Tell us about yourself”) especially for girls and that gender becomes increasingly salient as the child grows older.     

Age-related changes in grip force and dynamics of hand movement

The authors investigated whether older adults (n = 16; mean age = 65 years) increased grip force to compensate for load force fluctuations during up and down movements more than young adults did (n = 16; mean age = 24 years) and whether older and young adults exhibited similar adaptation of grip force to alterations in friction associated with changes in object surface texture. As previously reported, older adults used a higher level of grip force than young adults during static holding. Increased grip force was observed in the older group during movement. The increase was appropriate to the lower coefficient of friction estimated for the older group. In both groups, grip force was greater with a smooth than with a rough surface (the latter having the higher coefficient of friction) during static holding and during movement. Moreover, grip force modulation was equally well synchronized with load force fluctuation during movement in the two groups. The authors concluded that changes in organization of grip force with age are well adapted to change in hand-object interface properties. Elevated grip force in older adults does not necessarily signify a fundamental change in synchronizing grip force modulation with load force fluctuation.     

Risk and Prisoner's Dilemma: A Reinterpretation of Coombs' Re‐parameterization

We propose a model to measure risk in a prisoner's dilemma based on Coombs' (1973) re‐parameterization of the game as an individual risk decision‐making task that chooses between a gamble of cooperation and another gamble of defection. Specifically, we propose an index, r, to represent the risk associated with cooperation relative to defection. In conjunction with Rapoport's (1967) index of cooperation (K), our formulation of risk allows us to construct games that vary in risk (as indexed by r) while controlling for cooperativeness (as indexed by K). Following utility analysis that models risk seeking as a convex utility function and risk averse as a concave function, we predict that risk‐seeking people cooperate more in games that the cooperation choice is more risky, whereas risk‐averse people cooperate more in games that the cooperation choice is less risky. In the three studies that we varied game parameters, used different measures of risk orientation and prosocial orientation and used different experimental procedures, we found robust results supporting our predictions. Theoretical analysis of our formulation further suggests that risk and cooperativeness of a prisoner's dilemma game is not entirely independent. Games that have a higher cooperativeness index are necessarily more risky. Copyright © 2011 John Wiley & Sons, Ltd.     

Psychological correlates of violent and non-violent Hong Kong juvenile probationers

There is little known about Hong Kong juvenile offenders on probation. The purpose of this study was to compare Hong Kong juvenile violent with non-violent probationers on static demographic and psychological variables. The study comprised 109 male juvenile probationers aged 14-20 years (M = 16.97, SD = 1.44) in community transitional housing; 34 were adjudicated for violent offenses, while 75 were non-violent. The Rosenberg Self-Esteem Scale (RSES), Satisfaction with Life Scale (SWLS), Social Bonding Scale-Theft (SBS-T), Social Bonding Scale-Violent Crime (SBS-VC), Positive and Negative Affect Scales (PANAS), Impulsiveness Scale-Short Form (IS-SF) and CRIME-PICS II were administered to measure self-esteem, life satisfaction, social bond, positive and negative affect, impulsivity, pro-offending attitudes, and self-perceived life problems. Data on onset age of delinquent behavior, age of first adjudication, number of prior adjudications, and frequency of self-reported delinquency in the past year were also collected. t-tests were consistent with significant differences for violent offenders including higher self-esteem (p < 0.05). Non-violent offenders self-reported significantly more theft (p < 0.05) with a tendency to deny victim hurt more often (p < 0.01); 76.5% of violent offenders self-reported both violent and non-violent crime, while 58.7% of non-violent offenders reported only non-violent crime. For violent and non-violent offenders, the onset of delinquency was inversely related to the frequency of self-reported delinquency. Using ordinary least-squares (OLS) regression analyses, self-anticipated violent reoffending risk was predicted by age of onset, frequency of self-reported delinquency, social bond (inversely), and impulsivity, while non-violent reoffending risk was predicted by the number of prior convictions and self-reported delinquency. Only two psychological correlates, social bond and impulsivity, were related to violent delinquency; interventions are suggested.