Evidence for an error deadzone in compensatory tracking

Humans and monkeys show intermittent arm movements while tracking moving targets. This intermittency has been explained by postulating either a psychological refractory period after each movement and/or an error deadzone, an area surrounding the target within which movements are not initiated. We present a technique to detect and quantify the size of this deadzone, using a compensatory tracking paradigm that distinguishes it from a psychological refractory period. An artificial deadzone of variable size was added around a visual target displayed on a computer screen. While the subject was within this area, he received visual feedback that showed him to be directly on target. The presence of this artificial deadzone could affect tracking performance only if it exceeded the size of his intrinsic deadzone. Therefore, the size of artificial deadzone at which performance began to be affected revealed the size of the intrinsic deadzone. Measured at the subjects' eye, the deadzone was found to vary between 0.06 and 0.38 degrees, depending on the tracking task and viewing conditions; on the screen, this range was 1.3 mm to 3.3 mm. It increased with increasing speed of the target, with increasing viewing distance, and when the amplitude of the movement required was reduced. However, the deadzone size was not significantly correlated with the subjects' level of performance. We conclude that an intrinsic deadzone exists during compensatory tracking, and we suggest that its size is set by a cognitive process not simply related to the difficulty of the tracking task.     

Backward walking: a simple reversal of forward walking?

The purpose of this study was to determine whether backward walking represented a simple temporal reversal of forward walking and, hence, could be controlled by a reversed cycling of the same group of neurons. Electromyographic (EMG), joint angle, joint moment, and joint muscle power patterns were compared for forward and backward walking, in 6 subjects. The joint angle patterns with the time-base of the backward walking reversed were similar, with the exception of the ankle. The moment patterns were similar except for the knee, whereas the joint muscle powers were almost reversed-polarity images of each other. This suggests that somewhat similar muscle activation patterns could be used to produce both modes of locomotion, but the temporal cycling of muscle contraction would be reversed: Concentric muscle activity in forward walking would become eccentric activity in backward walking, and visa versa. The EMG results generally supported these findings.     

A personal experience of supervision

TTte author's personal experience and perspective as a feminist counsellor and supervisee is explored. Some key boundary issues are identified which have brought about some important learning for her. These examples illustrate the crucial importance of an awareness of gender issues within both the counselling and the supervisory relationship.     

Two-dimensional reward evaluation in mice

Animal Cognition - When choosing among multi-attribute options, integrating the full information may be computationally costly and time-consuming. So-called non-compensatory decision rules only...     

Intonation does aid serial recall after all

Psychonomic Bulletin & Review - A sequence of spoken digits is easier to recall if the digits are grouped into smaller chunks (e.g., through the insertion of pauses). It has been claimed that...     

Situating social influence processes: dynamic, multidirectional flows of influence within social networks.

Social psychologists have studied the psychological processes involved in persuasion, conformity, and other forms of social influence, but they have rarely modeled the ways influence processes play out when multiple sources and multiple targets of influence interact over time. However, workers in other fields from sociology and economics to cognitive science and physics have recognized the importance of social influence and have developed models of influence flow in populations and groups-generally without relying on detailed social psychological findings. This article reviews models of social influence from a number of fields, categorizing them using four conceptual dimensions to delineate the universe of possible models. The goal is to encourage interdisciplinary collaborations to build models that incorporate the detailed, microlevel understanding of influence processes derived from focused laboratory studies but contextualized in ways that recognize how multidirectional, dynamic influences are situated in people's social networks and relationships.     

The nature of intrusive memories after trauma: the warning signal hypothesis

Individuals who had experienced a range of different traumas were asked to describe the quality and content of their intrusive memories. Visual intrusions were the most common, and thoughts were uncommon. Intrusion quality varied little with type of trauma. Intrusive memories commonly consisted of stimuli that were present immediately before the traumatic event happened or shortly before the moments that had the largest emotional impact (i.e., when the meaning of the event became more traumatic). It is suggested that intrusive memories are about stimuli that through temporal association with the trauma acquired the status of warning signals, i.e., stimuli that if encountered again would indicate impending danger. This explains why intrusive memories are accompanied by a sense of serious current threat. The warning signal hypothesis may be useful in guiding therapists in identifying the moments with the largest emotional impact that will need reprocessing in treatment, and in educating patients about the nature of reexperiencing symptoms.     

Personal Constructs of Mind-Body Identity in People Who Experience Medically Unexplained Symptoms

“Medically unexplained symptoms” (MUS) refers to chronic physical symptoms without a clear medical cause, which produce significant levels of distress and functional impairment. This project modified the repertory grid technique to explore how twenty participants experiencing MUS construed self and others in bodily and psychological ways. Findings suggested that symptoms are well integrated within participants' wider mind–body construct systems. Increased distance between how self in general is construed compared to self when symptoms are worst was associated with reduced anxiety. Measuring intrapersonal and interpersonal implicative dilemmas suggested that moral and relational construing of identity is affected by MUS.     

Resource control and status as stimuli for arousing power motivation: An American-Chinese comparison

In this paper, we analyze power motivation from a cross-cultural perspective. Power motivation has been mainly studied within the Western culture. However, previous research suggests that some contours and nuances of power and power motivation may be culturally specific. In this article, we analyze cultural differences between American and Chinese students in how power motivation is aroused. Drawing from the cross-cultural literature, we propose that having decision-making control over resources increases levels of power motivation among Americans but not Chinese, whereas status-elevation increases power motivation among both Americans and Chinese. These hypotheses were tested experimentally with resource-control, status-elevation, and neutral conditions. The first hypothesis was fully supported, but the second one was only partially supported. Levels of power motivation in the neutral condition (i.e., dispositional power motives) were similar for American and Chinese participants, but power motivation arousal was greater for Americans than Chinese, in both power arousal conditions. These findings contribute to our understanding of the power motivation construct in a non-Western context.