REVIEW OF HEYMAN'S ADDICTION: A DISORDER OF CHOICE

Gene Heyman's Addiction: A Disorder of Choice (2009) advances the important, albeit controversial, view that addiction is not a chronic, relapsing brain disease, but instead is an example of typical everyday choice that is both voluntary and self‐destructive. This review highlights Heyman's arguments for conceptualizing addiction as choice and discusses the utility of the treatment implications that are derived from the melioration model in which Heyman frames addiction. Self‐control and behavioral economics are presented as additional complementary frameworks for understanding addiction as choice, from which pragmatic, evidence‐based treatments for addiction (e.g., contingency management) might more easily be derived.     

Quadriceps Torque,Peak Variability and Strength Endurance in Patients after Anterior Cruciate Ligament Reconstruction: Impact of Local Muscle Fatigue

Abstract

We tested if ACL-reconstructed participants show a decreased quadriceps torque, a lower muscle endurance capacity and a higher peak torque variability compared to unimpaired control participants prior to and following local muscle fatigue. Participants (n?=?19, 10 women; 25?±?5yrs.) with unilateral hamstrings autograft ACL-reconstruction and a matched unimpaired control group were recruited. Participants performed two maximal isometric voluntary force (MIVF) contractions of the knee extensors. In between, standardized local muscle fatigue was induced. ACL-reconstructed knees display a lower peak torque of the knee extensors in comparison to the contralateral limb (3.2?±?.3Nm/kg vs. 3.5?±?.3 Nm/kg). Peak torque variability and fatigue resistance were not affected by local muscle fatigue (p > .05). Participants with ACL-reconstructed knees show a persistent quadriceps muscle dysfunction. This dysfunction and lower limb side asymmetries might be risk factors for ACL re-ruptures.     

Corralling the Ingroup: Deviant Derogation and Perception of Group Variability

ABSTRACT

Two experiments investigated the relationship between the evaluation of a deviant group member and the perceived group variability among participants with varying degrees of ingroup identification. In Experiment 1 (N?=?79) ingroup identification was negatively associated with perceived ingroup variability following the presentation of a deviant ingroup member. This relationship was mediated by ratings of the deviant: the stronger the identification, the more negatively the deviant was evaluated, and the more homogeneous the ingroup was perceived. These effects were replicated in Experiment 2 (N?=?169), which also showed that there was no association between ingroup identification and the representation of the outgroup following exposure to a deviant outgroup member. The findings suggest that deviant derogation may serve to isolate undesirable members from the rest of the ingroup and protect the group's identity.     

SAVING THE BEST FOR LAST? A CROSS-SPECIES ANALYSIS OF CHOICES BETWEEN REINFORCER SEQUENCES

Two experiments were conducted to compare choices between sequences of reinforcers in pigeon (Experiment 1) and human (Experiment 2) subjects, using functionally analogous procedures. The subjects made pairwise choices among 3 sequence types, all of which provided the same overall reinforcerment rate, but differed in their temporal patterning. Token reinforcement schedules were used in both experiments and the type of exchange schedule varied across blocks of sessions. Some conditions permitted immediate exchange of tokens for consumable reinforcers (food for pigeons, video access for humans); in other conditions, tokens accumulated and were exchanged for consumable reinforcers only at the end of the sequence. Choice patterns in the immediate-exchange conditions were generally similar across species, with both pigeons and humans preferring sequences with the shortest delay to the initial reinforcer in the series. The results are broadly consistent with models of temporal discounting expanded to include the impact of sequences of delayed reinforcers acting in parallel from the time of the choice. Preferences were less consistent with discounting models in the delayed exchange conditions. Questionnaire data gathered at the end of the experiment were consistent with prior results of questionnaire studies, but showed no straightforward relation to the observed choice patterns, urging caution in the extrapolation of results from one decision-making domain to the other.     

Looking Ahead: Questions for and About Behavioral Scientists and Practitioners

In this article Robin B. Jarrett reflects on the early years in which female investigators were a minority in the field and on her participation in the Trailblazers' panel discussion at the Association for Behavioral and Cognitive Therapies on November 29, 2009. Dr. Jarrett writes these reflections in the form of a letter to current and future professionals (of all demographics) dedicated to behavioral science and its practice; she poses questions about what the future may hold.     

Increasing perceived variability reduces prejudice and discrimination

We examined whether increasing individuals' perceived variability of an out-group reduces prejudice and discrimination toward its members. In a series of 4 laboratory and field experiments, we attracted participants' attention to either the homogeneity or the heterogeneity of members of an out-group, and then measured their attitudes or behaviors. Perceived variability was manipulated by making subgroups salient, by portraying the out-group members as having diverse opinions, by making salient that out-group members have different characteristics, or by asking participants to think about differences among out-group members. Prejudice and discrimination were measured in terms of self-reported attitudes, distribution of rewards, helping an out-group confederate, and evaluation of an out-group candidate in a simulated hiring decision. In all experiments, perceived variability decreased prejudice and discrimination. This effect may be due to the fact that perceived variability decreases the role of group membership in the production of attitudes and behaviors toward other individuals.     

Reinforcing saccadic amplitude variability

Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we reinforced the least frequent saccadic amplitudes to increase variability, and then reinforced the central part of the amplitude distributions to reduce variability. The target was placed at a constant distance from the fovea after the saccade to maintain the postsaccadic visual signal constant and an auditory reinforcement was delivered depending on saccadic amplitude. The second experiment tested the effects of the contingency. We reinforced high levels of variability in 4 participants, whereas 4 other participants were assigned to a yoked control group. On average, saccadic amplitude standard deviations were doubled while the medians remained mostly unchanged in the experimental participants in both experiments, and variability returned to baseline level when low variability was reinforced. In the control group no consistent changes in amplitude distributions were observed. These results, showing that variability can be reinforced, challenge the idea of a stochastic neural noise. We instead propose that selection processes constrain saccadic amplitude distributions.     

Contextual influences on resistance to disruption in children with intellectual disabilities

Training context can influence resistance to disruption under differing reinforcement schedules. With nonhumans, when relatively lean and rich reinforcement schedules are experienced in the context of a multiple schedule, greater resistance is found in the rich than the lean component, as described by behavioral momentum theory. By contrast, when the schedules are experienced in separated blocks of sessions (i.e., as single schedules), resistance is not consistently greater in either component. In the current study, two groups of 6 children with intellectual disabilities responded to stimuli presented in relatively lean or rich components. For both, reinforcers were delivered according to the same variable-interval reinforcement schedule; additionally, the rich component included the delivery of response-independent reinforcers. The Within group was trained on a multiple schedule in which lean and rich components alternated regularly within sessions; the Blocked group was trained on two single schedules in which sessions with either the lean or rich schedule were conducted in successive blocks. Disruption tests presented a concurrently available alternative stimulus disrupter signaling the availability of tangible reinforcers. All 6 Within participants showed greater resistance to disruption in the rich component, consistent with behavioral momentum theory. By contrast, there was no consistent or significant difference in resistance for Blocked participants. This finding is potentially relevant to the development of interventions in applied settings, where such interventions often approximate single schedules and include response-independent reinforcers.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

Individuals differ in the attentional blink: Mental speed and intra-subject stability matter

The failure to correctly report two targets (“T₁”, “T₂”) that follow each other in close temporal proximity has been called the “attentional blink” (AB). The AB has, so far, mainly been studied using experimental approaches. The present studies investigated individual differences in AB performance, revealing (among further findings) a high positive correlation between the accuracies of detecting the two targets correctly (r = 0.69); and between T₂∣T₁ accuracy and psychometric intelligence (0.41 ≤ r ≤ 0.43) and RT variability in short-term and working memory (− 0.38 ≤ r ≤ − 0.45). Together, these results support important aspects of major theoretical accounts of the AB from an individual differences perspective and introduce intelligence and intra-subject stability as contributing factors in AB performance.