Relative damping improves linear mass-spring models of goal-directed movements

A limitation of a simple linear mass-spring model in describing goal directed movements is that it generates rather slow movements when the parameters are kept within a realistic range. Does this imply that the control of fast movements cannot be approximated by a linear system? In servo-control theory, it has been proposed that an optimal controller should control movement velocity in addition to position. Instead of explicitly controlling the velocity, we propose to modify a simple linear mass-spring model. We replaced the damping relative to the environment (absolute damping) with damping with respect to the velocity of the equilibrium point (relative damping). This gives the limb a tendency to move as fast as the equilibrium point. We show that such extremely simple models can generate rapid single-joint movements. The resulting maximal movement velocities were almost equal to those of the equilibrium point, which provides a simple mechanism for the control of movement speed. We further show that peculiar experimental results, such as an 'N-shaped' equilibrium trajectory and the difficulties to measure damping in dynamic conditions, may result from fitting a model with absolute damping where one with relative damping would be more appropriate. Finally, we show that the model with relative damping can be used to model subtle differences between multi-joint interceptions. The model with relative damping fits the data much better than a version of the model with absolute damping.     

Too proud to let go: narcissistic entitlement as a barrier to forgiveness

Narcissistic entitlement impedes forgiveness in ways not captured by other robust predictors (e.g., offense severity, apology, relationship closeness, religiosity, Big Five personality factors), as demonstrated in 6 studies. Narcissistic entitlement involves expectations of special treatment and preoccupation with defending one's rights. In Study 1, entitlement predicted less forgiveness and greater insistence on repayment for a past offense. Complementary results emerged from Study 2, which used hypothetical transgressions, and Study 3, which assessed broad forgiveness dispositions. Study 4 examined associations with the Big Five, and Study 5 extended the findings to a laboratory context. Study 6 demonstrated that entitlement predicted diminished increases in forgiveness over time. Taken together, these results suggest that narcissistic entitlement is a robust, distinct predictor of unforgiveness.     

The dual effect of context on memory of related and unrelated themes: Discrimination at encoding and cue at retrieval

The influence of contextual factors on encoding and retrieval in recognition memory was investigated using a retroactive interference paradigm. Participants were randomly assigned to four context conditions constructed by manipulating types of presentation modality (pictures vs words) for study, interference, and test stages, respectively (ABA, ABB, AAA, & AAB). In Experiment 1 we presented unrelated items in the study and interference stages, while in Experiment 2 each stage contained items from the same semantic category. The results demonstrate a dual role for context in memory processes-at encoding as well as at retrieval. In Experiment 1 there is a hierarchical order between the four context conditions, depending on both target-test and target-interference contextual similarity. Adding a categorical context in Experiment 2 helped to specify each list and therefore better distinguish between target and interferer information, and in some conditions compensated for their perceptual similarity.     

Buffering against weight gain following dieting setbacks: An implicit theory intervention

Research on implicit theories suggests that incremental beliefs—that attributes are malleable—can help buffer people against the adverse effects of setbacks on goal achievement. We conducted a longitudinal experiment to examine whether an incremental beliefs intervention could help dieters manage their body weight in the face of severe dieting setbacks. To explore the efficacy of our incremental beliefs intervention, we randomly assigned individuals to a control, a knowledge, or an incremental beliefs condition. In addition to examining the main effect of intervention condition on weight-loss across a 12-week period, we also tested the hypothesis that although participants assigned to the control or knowledge intervention condition would gain more weight as dieting setbacks became more severe, participants assigned to the incremental beliefs condition would not. Results supported this hypothesis: Incremental beliefs protected against setback-related weight-gain. Implications for integrating implicit beliefs interventions with obesity relapse prevention programs are discussed.     

Putting the brakes on aggression toward a romantic partner: the inhibitory influence of relationship commitment

Why do people behave aggressively toward romantic partners, and what can put the brakes on this aggression? Provocation robustly predicts aggression in both intimate and nonintimate relationships. Four methodologically diverse studies tested the hypothesis that provocation severity and relationship commitment interact to predict aggression toward one's romantic partner, with the aggression-promoting effects of provocation diminishing as relationship commitment increases. Across all four studies, commitment to one's romantic relationship inhibited aggression toward one's partner when individuals were severely (but not mildly) provoked. Study 4 tested the hypothesis that this Partner Provocation × Commitment interaction effect would be strong among individuals high in dispositional tendencies toward retaliation but weak (perhaps even nonexistent) among individuals low in such tendencies. Discussion emphasizes the importance of understanding instigating, impelling, and inhibiting processes in the perpetration of aggression toward intimate partners.     

The evolutionary armistice: attachment bonds moderate the function of ovulatory cycle adaptations

Natural selection modified the attachment-behavioral system to bond adult mating partners in early members of the genus Homo, thus facilitating increased investment, especially paternal investment, in offspring. Previously existing adaptations that fostered intersexual conflict (e.g., ovulatory adaptations) could have threatened attachment bonds; therefore, the attachment-behavioral system might have evolved the ability to mute or refocus such adaptations for the purpose of strengthening the bond. Two studies offer support for this prediction. Women who were strongly attached to their romantic partner revealed positive associations of fertility with reports of romantic physical intimacy, but these associations were negative among unbonded women. This moderational effect of attachment bond strength was robust beyond dispositional attachment anxiety and avoidance, relationship satisfaction, relationship commitment, and partner physical attractiveness, none of which revealed robust moderational effects. Findings highlight how researchers can use the timeline of hominid evolution (i.e., phylogeny) as a tool to complement functional, adaptationist hypotheses.     

Analysis of methods to determine the latency of online movement adjustments

When studying online movement adjustments, one of the interesting parameters is their latency. We set out to compare three different methods of determining the latency: the threshold, confidence interval, and extrapolation methods. We simulated sets of movements with different movement times and amplitudes of movement adjustments, all with the same known latency. We applied the three different methods in order to determine when the position, velocity, and acceleration of the adjusted movements started to deviate from the values for unperturbed movements. We did so both for averaged data and for the data of individual trials. We evaluated the methods on the basis of their accuracy and precision, and according to whether the latency was influenced by the intensity of the movement adjustment. The extrapolation method applied to average acceleration data gave the most reliable estimates of latency, according to these criteria.     

The bisection point across variants of the task

Bisection tasks are used in research on normal space and time perception and to assess the perceptual distortions accompanying neurological disorders. Several variants of the bisection task are used, which often yield inconsistent results, prompting the question of which variant is most dependable and which results are to be trusted. We addressed this question using theoretical and experimental approaches. Theoretical performance in bisection tasks is derived from a general model of psychophysical performance that includes sensory components and decisional processes. The model predicts how performance should differ across variants of the task, even when the sensory component is fixed. To test these predictions, data were collected in a within-subjects study with several variants of a spatial bisection task, including a two-response variant in which observers indicated whether a line was transected to the right or left of the midpoint, a three-response variant (which included the additional option to respond “midpoint”), and a paired-comparison variant of the three-response format. The data supported the model predictions, revealing that estimated bisection points were least dependable with the two-response variant, because this format confounds perceptual and decisional influences. Only the three-response paired-comparison format can separate out these influences. Implications for research in basic and clinical fields are discussed.