Tactile-Based Pantomime Grasping: Knowledge of Results is Not Enough to Support an Absolute Calibration

Tactile-based pantomime-grasping requires that a performer use their right hand to ‘grasp’ a target previously held in the palm of their opposite hand – a task examining how mechanoreceptive (i.e., tactile) feedback informs the motor system about an object property (i.e., size). Here, we contrasted pantomime-grasps performed with (H+) and without (H?) haptic feedback (i.e., thumb and forefinger position information derived from the grasping hand touching the object) with a condition providing visual KR (VKR) related to absolute target object size. Just-noticeable-difference (JND) scores were computed to determine whether responses adhered to – or violated – Weber's law. JNDs for H+ trials violated the law, whereas H? and VKR trials adhered to the law. Accordingly, results demonstrate that haptic feedback – and not KR – supports an absolute tactile-haptic calibration.     

Assessing preference for reinforcers using demand curves, work-rate functions, and expansion paths

Much research has focused on the effects of environmental variability on foraging decisions. However, the general pattern of preference for variability in delay to reward and aversion to variability in amount of reward remains unexplained a either a mechanistic or a functional level. Starlings' preferences between a fixed and a variable option were studied in two treatments, A and D. The fixed option was the same in both treatments (20-s fixed-interval delay, five units food). In Treatment A the variable option gave two equiprobable amounts of food (20-s delay, three or seven units) and in D it gave two equiprobable delays to food (2.5-s or 60.5-s delays, five units). In both treatments the programmed ratio [amount/(intertrial interval+latency+delay)] in the fixed option equaled the arithmetic mean of the two possible ratios in the variable option (ITI = 40 s, latency = 1 s). The variable option was strongly preferred in Treatment D and was weakly avoided in Treatment A. These results are discussed in the light of two theoretical models, a form of constrained rate maximization and a version of scalar expectancy theory. The latter accommodates more of the data and is based on independently verifiable assumptions, including Weber's law.     

Temporal discrimination and a free-operant psychophysical procedure.

Pigeons were presented a series of keylight time periods (separated by blackouts) during which two response keys were lit, one by blue light and the other either by orange or green. Blue-key responses changed the color on the other key. Orange-key responses sometimes produced food during the first half of a time period; green-key responses sometimes produced food during the second half. In three experiments, the probability of a green-key response increased as a function of elapsed time. Experiment 1 compared performance when the duration of the keylight periods was varied across a wide range. Discrimination of performance was similar across the range of durations. Experiment 2 varied both relative reinforcement rate and the local reinforcement rate for orange-key and green-key responses. These manipulations produced changes in response bias but not discrimination sensitivity. Experiment 3 varied the local temporal placement of reinforcers within time periods and demonstrated that choice behavior was affected by differential reinforcement at different points during the time periods. The results were consistent with previous research on duration discrimination that used psychophysical trials procedures.     

Action‐semantic and syntactic deficits in subjects at risk for Huntington's disease

Frontostriatal networks play critical roles in grounding action semantics and syntactic skills. Indeed, their atrophy distinctively disrupts both domains, as observed in patients with Huntington's disease (HD) and Parkinson's disease, even during early disease stages. However, frontostriatal degeneration in these conditions may begin up to 15 years before the onset of clinical symptoms, opening avenues for pre‐clinical detection via sensitive tasks. Such a mission is particularly critical in HD, given that patients’ children have 50% chances of inheriting the disease. Against this background, we assessed whether deficits in the above‐mentioned domains emerge in subjects at risk to develop HD. We administered tasks tapping action semantics, object semantics, and two forms of syntactic processing to 18 patients with HD, 19 asymptomatic first‐degree relatives, and sociodemographically matched controls for each group. The patients evinced significant deficits in all tasks, but only those in the two target domains were independent of overall cognitive state. More crucially, relative to controls, the asymptomatic relatives were selectively impaired in action semantics and in the more complex syntactic task, with both patterns emerging irrespective of the subjects’ overall cognitive state. Our findings highlight the relevance of these dysfunctions as potential prodromal biomarkers of HD. Moreover, they offer theoretical insights into the differential contributions of frontostriatal hubs to both domains while paving the way for innovations in diagnostic procedures.     

Child Safety in Australian Family Law: Responsibilities and Challenges for Social Science Experts in Domestic Violence Cases

Understanding the potentially adverse effects of exposure to domestic violence on children is increasing in the Western world. However, in Australian family law, there remain challenges in centralising the special needs of these children in cases before the family courts in the determination of their best interests. This article draws on some key findings of a small qualitative study to highlight and discuss some of the barriers that need to be overcome in order for social science experts to enhance the courts' capacity to protect child subjects of proceedings from possible future harm.     

Endings as gain: The capacity to end and its role in creating space for growth

The paper describes an application of child psychotherapy in a paediatric setting. It examines the crucial part that attention to endings played in a clinical intervention where the phantasy of going on for ever threatened to inhibit growth. Case material is used to illustrate the different meanings and functions of endings and their significance in terms of parenting issues and developmental tasks. In this context the concept of negative elasticity is put forward as a useful tool for exploring the nature of boundaries. The final part of the paper focuses on the value of the external-reality experience of ending, its relationship to potential professional omnipotence and the importance of sustaining a tension between inner- and outer-world factors.