Affordance, proper function, and the physical basis of perceived heaviness

The physical basis of perceived heaviness requires consideration of the haptic perceptual system's role in controlling actions (the system's proper function) and the relation of an object's inertial properties to properties of the human movement system (the object's affordance). We show that the mass of a wielded object and particular scalar variables calculated from the object's inertia tensor combine linearly in determining perceived heaviness. The tensor-derived scalars reflect the symmetry and volume of the corresponding inertia ellipsoid. These measures bear directly on the object's wieldability, that is, on the patterning and level of muscular forces required to move the object in a controlled fashion.     

The norm of self-interest

The self-interest motive is singularly powerful according to many of the most influential theories of human behavior and the layperson alike. In the present article the author examines the role the assumption of self-interest plays in its own confirmation. It is proposed that a norm exists in Western cultures that specifies self-interest both is and ought to be a powerful determinant of behavior. This norm influences people's actions and opinions as well as the accounts they give for their actions and opinions. In particular, it leads people to act and speak as though they care more about their material self-interest than they do. Consequences of misinterpreting the "fact" of self-interest are discussed.     

Posttraumatic stress disorder in a national sample of female and male Vietnam veterans: risk factors, war-zone stressors, and resilience-recovery variables

Relationships among pretrauma risk factors (e.g., family instability, childhood antisocial behavior), war-zone stressors (e.g., combat, perceived threat), posttrauma resilience-recovery variables (e.g., hardiness, social support), and posttraumatic stress disorder (PTSD) symptom severity were examined. Data from a national sample of 432 female and 1,200 male veterans were analyzed using structural equation modeling. For both genders, direct links to PTSD from pretrauma, war-zone, and posttrauma variable categories were found; several direct associations between pretrauma and posttrauma variables were documented. Although war-zone stressors appeared preeminent for PTSD in men, posttrauma resilience-recovery variables were more salient for women. Researchers, policymakers, and clinicians are urged to take a broad view on trauma and its sequelae, especially regarding possible multiple exposures over time and the depletion and availability of important resources.     

Sex, competitiveness, and intimacy in same-sex friendship in Hong Kong adolescents

One of the alleged reasons that males report lower intimacy in same-sex friendships than females is that males tend to be more competitive than females, but this assumption has not been empirically tested. In the current study, 121 Hong Kong adolescents filled out Chinese versions of the Intimate Friendship Scale and the Competitiveness Index. As predicted, females reported having more intimate same-sex relationships than males, and they scored lower on competitiveness than males. However, the correlations between scores on the Competitiveness Index and the Intimate Friendship subscales were small and nonsignificant, suggesting that the sex difference in intimacy was not a function of competitiveness.     

Stability and change in longitudinal water-level task performance.

Three longitudinal samples of children (N = 481), 8 to 16 years old, were assessed 3 times at yearly intervals on 8 water-level items. The within-child change in task performance over age is viewed as a stochastic process of the child changing or remaining in 1 of 3 latent (strategy) states: (a) bottom-parallel responders, (b) random responders, or (c) accurate responders. A random-effects binomial mixture distribution is used to model performance at each age. Change over age is gauged by a stochastic transition model. Although there was improvement in task performance over age, the more general finding is that strategy stability, not change, is most typical.     

Are Reaching Movements Planned to be Straight and Invariant in the Extrinsic Space? Kinematic Comparison Between Compliant and Unconstrained Motions

Two main questions were addressed in the present study. First, does the existence of kinematic regularities in the extrinsic space represent a general rule? Second, can the existence of extrinsic regularities be related to specific experimental situations implying, for instance, the generation of compliant motion (i.e. a motion constrained by external contact)? To address these two questions we studied the spatio-temporal characteristics of unconstrained and compliant movements. Five major differences were observed between these two types of movement: (1) the movement latency and movement duration were significantly longer in the compliant than in the unconstrained condition; (2) whereas the hand path was curved and variable according to movement direction for the unconstrained movements, it was straight and invariant for the compliant movements; (3) whereas the movement end-point distribution was roughly circular for the unconstrained movements, it was consistently elongated and typically oriented in the movement direction for the compliant movements; (4) whereas constant errors varied as a function of target eccentricity for the unconstrained movements, they were independent of this factor for the compliant movements; (5) the instruction to move the final effector along a straight line path influenced the characteristics of the unconstrained movements but not the characteristics of the compliant movements. When considered together, the previous observations suggest that compliant and unconstrained movements involve different planning strategies. Our data support the hypothesis that unconstrained motions, unlike compliant motions, are not programmed to follow a straight line path in the extrinsic space. This observation provides a theoretical frame of reference within which some apparently contradictory results reported in the movement generation literature may be explained.     

Behavioral Research on the Severe and Persistent Mental Illnesses

We are honored to introduce the special series highlighting behavioral research on the severe and persistent mental illnesses (SPMIs) that appears in this issue of Behavior Therapy. We begin this series by providing a succinct overview of this category of disorders, noting briefly their impact, cost, etiology, and management. We then identify four recent advances in the care of persons living with a SPMI, and provide an overview of the six articles that appear in this series. The series recognizes and showcases outstanding behavioral research, and seeks to encourage new and continuing participation by behavior therapists in the care of persons living with a SPMI.     

The mutual effects between job resources and mental health: a prospective study among Dutch youth

The current study construes the relation between job resources (such as job autonomy, skill utilization, and variety) and mental health as a reciprocal process. Following conservation of resources theory (S. E. Hobfoll, 1989), the author expected job resources to have a positive effect on mental health. Poor mental health was assumed to impede workers' attempts to maintain or enhance their job resources either by changing the content of their jobs or attempting to find another (less distressing) job. Longitudinal data from a representative sample of 699 Dutch youth were analyzed with analysis of variance and covariance structure modeling. The results provided good support for the proposition that job resources and mental health mutually influence each other. Limitations and implications of the study are discussed.     

The role of vocabulary ability during visual word recognition in younger and older adults

The role that vocabulary ability plays in adult age differences in word recognition was investigated. In Experiment 1, 44 older adults (ages 61-93 years) were compared with 44 younger adults (ages 18-39 years) on a standard lexical-decision task, with ambiguous words, unambiguous words, and pseudowords serving as stimuli. In Experiment 1, the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981) vocabulary performance was uncontrolled across the younger and older adults, and the older adults had higher WAIS-R scores. There was no Group x Stimulus interaction. In Experiment 2, the data from the same 44 older adults were compared with data from a new sample of 44 younger adults (ages 18-44). Both groups were then matched on WAIS-R performance. Results revealed a significant Group x Stimulus interaction. Reaction time differences between the younger and older groups on the ambiguous words and unambiguous words were identical. The differences in reaction times for words and pseudowords were greater in the older adults. The importance of vocabulary ability during word recognition and lexical processing is discussed.     

Parenting characteristics and adolescent psychological well-being: a longitudinal study in a Chinese context

In this longitudinal study, the relationships between perceived parenting characteristics and adolescent psychological well-being were examined in a sample of Hong Kong Chinese adolescents (N = 378). The results indicated that global parenting styles and specific parenting behaviors are concurrently related to hopelessness, life satisfaction, self-esteem, purpose in life, and general psychiatric morbidity at Time 1 and Time 2. Longitudinal and prospective analyses (Time 1 predictors of Time 2 criterion variables) suggested that the relations between parenting characteristics and adolescent psychological well-being are bidirectional in nature. The results indicated that the strengths of association between perceived parenting characteristics and adolescent psychological well-being are stronger in female than in male adolescents. Relative to maternal parenting characteristics, paternal parenting was found to exert a stronger influence on adolescent psychological well-being.