Prehension in children and adults: The effects of object size

Studies of visually goal-directed arm movements in adults have shown that various task constraints such as intention, context, and object properties affect different kinematic characteristics of the movement components (Jeannerod, 1984; MacKenzie et al., 1987; Marteniuk et al., 1987, 1990; Paulignan et al., 1991; Soechting, 1984). The purpose of the present study was to compare the effects of varying object size on the kinematics of reaching and grasping in both children and adults. Five children aged 9–10 years and five adults aged 18–24 years reached for and grasped three different sized cubes. Results revealed that object size had the same effect on the planning and control of reaching and grasping movements in children as in adults. Unlike adults, however, children in this age range spent more time in deceleration and reached peak aperture much later in the movement trajectory. The results were interpreted as immature integration of the visual and proprioceptive systems in 9–10 year olds. The implications of these findings for further examining developmental trends in prehension are discussed.PsycINFO classification: 2330     

时间顺序信息加工的实验研究

该研究运用Ｇｌｕｃｋｓｂｅｒｇ和ＭｃＣｌｏｓｋｅｙ（１９８１）的问答模型,通过两个实验检查了项目的时序信息是通过项目学习时的时序编码获得的,还是在项目提取时建构的;时序加工是自动的,还是控制的两个问题。结果表明：项目的时序信息是通过项目学习时的时序编码获得的,而不是在项目提取时建构的;时序信息的编码是控制的。     

The role of somatosensory stimulation in social phobia—An analysis of hand coordination in patients and therapeutic dyads during psychodynamic psychotherapy

In the psychotherapeutic treatment of social phobia, the hand movement behaviour exhibited during the interaction provides information about the success of the therapy. In particular, the degree of mutual somatosensory stimulation of the hands (hands moving on each other, as a unit, apart) appears to be relevant regarding the patient's mental state. To test this hypothesis, the present study investigates hand coordination in the course of psychotherapy in patients with and without symptom improvement and in the corresponding therapeutic dyads. Forty-two videos of patient–therapist dyads consisting of 21 patients (n = 11 non-improved; n = 10 improved; according to Liebowitz Social Anxiety Scale self-assessment) from the Social Phobia Research Network project were investigated in early psychotherapy sessions and in pre-last sessions. Hand movements of four randomised video sequences per dyad were analysed with NEUROGES^®-ELAN. Patients with non-improved symptoms displayed shorter act apart coordination and more act on each other coordination than patients with improved symptoms. Patients displayed more act apart and act on each other and less act as a unit coordination than therapists. In therapeutic dyads, act on each other coordination in early sessions, as well as short act apart coordination, was significantly related to non-improvement. Patients with non-improved symptoms are characterised by more hand coordination associated with a high degree of somatosensory stimulation serving self-regulation (act on each other), as well as short complex gestural expressions (act apart). Thus, hand coordination constitutes a progression and outcome parameter informing on somatosensory stimulation.     

Anticipation of ball location in low and high-skill performers: a developmental perspective

Objectives: To study how visual anticipatory capabilities develop in high and low-skill tennis players and the role of years of practice (i.e. experience). It was expected that with accumulated experience differences will increase with skill-level, in particular under conditions of fast visual exposure which results in minimal environmental information exposure.Method: Eighty tennis players divided into 4 age categories and 2 skill levels (high and low) were selected according to 4 criterion which ensured appropriate representation of skill-level and experience in tennis. Age categories were 8–11, 11–14, 14–18, and >18. Years of experience in the game were 2.12, 4.17, 6.5, and 12.4 years respectively. Players observed filmed segments of tennis strokes on a monitor, which varied in temporal occlusion conditions from −480 ms prior to ball-racquet contact to 320 ms after contact. After each exposure they were asked to indicate the final ball location. The radial, lateral, and depth distances were averaged for age and skill level.Design: A temporal occlusion paradigm was used in this study. The film was prepared with a camera positioned in the receiver's court. Eight strokes which best represent the game of tennis were chosen. Forty-eight segments were viewed and errors were calculated for each exposure.Result: High-skill tennis players gained more from practice and experience in developing visual anticipatory skills, but their perceptual advantage was not consistent across all stroke conditions, being at its greatest number in conditions of maximal temporal constraints.Conclusions: Differences in visual anticipatory capabilities exist between different skill levels at the outset of their development. These differences increase with experience, mainly after 6–7 years. Greater knowledge base does not always guarantee a superior anticipation of upcoming events and choosing the best decision.     

Influence of perceived emotion and gender on social motor coordination

Theorists have long postulated that facial properties such as emotion and sex are potent social stimuli that influence how individuals act. Yet extant scientific findings were mainly derived from investigations on the prompt motor response upon the presentation of affective stimuli, which were mostly delivered by means of pictures, videos, or text. A theoretical question remains unaddressed concerning how the perception of emotion and sex would modulate the dynamics of a continuous coordinated behaviour. Conceived in the framework of dynamical approach to interpersonal motor coordination, the present study aimed to address this question by adopting the coupled-oscillators paradigm. Twenty-one participants performed in-phase and anti-phase coordination with two avatars (male and female) displaying three emotional expressions (neutral, happy, and angry) at different frequencies (100% and 150% of the participant's preferred frequency) by executing horizontal rhythmic left-right oscillatory movements. Time to initiate movement (TIM), mean relative phase error (MnRP), and standard deviation of relative phase (SDRP) were calculated as indices of reaction time, deviation from the intended pattern of coordination, and coordination stability, respectively. Results showed that in anti-phase condition at 150% frequency, MnRP was lower with the angry and the female avatar. In addition, coordination was found to be more stable with the male avatar than the female one when both displaying neutral emotion. But the happy female avatar was found to elicit more stable coordination than the neutral female avatar. These results implied that individuals are more relaxed to coordinate with the female than the male, and the sensorimotor system becomes more flexible to coordinate with an angry person. It is also suggested social roles influence how people coordinate, and individuals attend more to interact with a happy female. In sum, the present study evidenced that social perception is embodied in the interactive behaviour during social interaction.     

Effect of Stroke on Joint Control during Reach-to-Grasp: A Preliminary Study

Abstract

We investigated changes in control of inter-segmental dynamics underlying upper extremity dyscoordination caused by stroke. Individuals with stroke and healthy individuals performed a natural reach-to-grasp movement. Kinetic analysis revealed that both groups rotated the shoulder by muscle torque and used interaction torque to rotate the elbow. However, individuals with stroke used interaction torque less than healthy individuals, actively suppressing a substantial portion of it. This resulted in inefficient use of active control and dyscoordination of the upper extremity. The degree of interaction torque suppression and inefficiency of active control at the elbow positively correlated with stroke severity. The increased interaction torque suppression can be a strategy used by individuals with stroke to compensate for deficient feedforward control of this torque.     

Decision by sampling

We present a theory of decision by sampling (DbS) in which, in contrast with traditional models, there are no underlying psychoeconomic scales. Instead, we assume that an attribute's subjective value is constructed from a series of binary, ordinal comparisons to a sample of attribute values drawn from memory and is its rank within the sample. We assume that the sample reflects both the immediate distribution of attribute values from the current decision's context and also the background, real-world distribution of attribute values. DbS accounts for concave utility functions; losses looming larger than gains; hyperbolic temporal discounting; and the overestimation of small probabilities and the underestimation of large probabilities.     

Reactivity of Tic Observation Procedures to Situation and Setting

Tic frequency was assessed and compared across home and clinic as well as three experimentally-manipulated situations in order to assess the phenomenon of tic reactivity. Forty-three youngsters with chronic tic disorder recruited from two geographically-distinct sites were videotaped over three weekly laboratory visits under each of the following conditions: (1) alone/camera present, (2) other present/camera present, and (3) alone/camera hidden. Contrary to expectation, more tics were observed during overt as compared to covert observation, while the presence of another person had no overall impact on tic expression. Mean tic counts obtained from clinic observation did not significantly differ from those obtained at home collected either one day before or after. Tic frequency counts were remarkably stable over the three weekly assessments both at home and clinic. Study findings are consistent with past observations that tic expression can be influenced by environmental factors and suggest the stability of tic frequency may exhibit greater temporal and setting stability than previously thought. The clinical and research implications of these results are discussed.     

Ageing effects on the attention demands of walking

Attention demands of walking were determined in six male and six female young adults (mean 26.3 yr) and 12 gender-matched healthy, active older adults (mean 71.1 yr) using a dual task procedure with a reaction time (RT) secondary task. In three conditions an auditory stimulus, a visual stimulus and both stimuli (auditory/visual) were presented. Relative to no-walking baselines, increased RT was found in all conditions revealing an attentional cost of normal walking. When participants traversed the laboratory walkway and also positioned one of their feet within a target area on the ground, attention demands were greater than in unconstrained walking. In the targeting task, RTs to the visual stimulus were longer than for the auditory stimulus due to the interference associated with viewing both the stimulus monitor and the foot-target. Older participants' RTs in the visual and auditory/visual conditions, but not in the auditory condition, were significantly longer than for the young group in both walking tasks but RTs for young and older adults were not different in no-walking baseline trials. Inspection of mean RT functions at time intervals following gait initiation (0-3000 ms from the first step) suggested a fluctuating attentional cost of walking with increased demands associated with contingencies requiring step length regulation. The findings have applied significance in demonstrating the possibility of increased falls and pedestrian accident risk in older individuals in dual task situations such as road crossing.