Voluntary action influences visual competition

Converging lines of evidence point to a strong link between action and perception. In this study, we show that this linkage plays a role in controlling the dynamics of binocular rivalry, in which two stimuli compete for perceptual awareness. Observers dichoptically viewed two dynamic rival stimuli while moving a computer mouse with one hand. When the motion of one rival stimulus was consistent with observers' own hand movements, dominance durations of that stimulus were extended and, remarkably, suppression durations of that stimulus were abbreviated. Additional measurements revealed that this change in rivalry dynamics was not attributable to observers' knowledge about the condition under test. Thus, self-generated actions can influence the resolution of perceptual conflict, even when the object being controlled falls outside of visual awareness.     

Voluntary action alters the perception of visual illusions

Attention, Perception, & Psychophysics - “Intentional binding” refers to the finding that people judge voluntary actions and their effects as having occurred closer together in time...     

Voluntary saccadic control in dyslexia

The role of eye-movement control in dyslexia is still unclear. Recent studies, however, confirmed that dyslexics show poor saccadic control in single and sequential target tasks. In the present study we investigated whether dyslexic subjects are impaired on an antisaccade task requiring saccades against the direction of a stimulus. Altogether, 620 subjects between the ages of 7 and 17 years were classified as dyslexics (N = 506) or control subjects (N = 114) on the grounds of the discrepancy between their intellectual abilities and reading/spelling achievements. All subjects performed an overlap prosaccade and a gap antisaccade task with 100 trials to each side of stimulation in random order. Variables analysed were the overall saccadic reaction time of both tasks; and from the antisaccade task the number of errors (prosaccades), the number of corrected errors, and the number of trials in which the subjects still failed to reach the side opposite the stimulus even after two saccades. An analysis of variance was carried out taking into account the development of saccadic behaviour with age and the differences between the groups. The results confirm development of saccade control with age, especially in the voluntary component (a frontal-lobe function) for both groups, but indicate that the antisaccade task performance, as measured by the error and the correction rate, is significantly worse in the dyslexic group at ages above 8 years. Up to 50% of the dyslexics performed the antisaccade task 1.5 standard deviations below the mean of the controls.     

Erratum to: Voluntary action alters the perception of visual illusions

Attention, Perception, & Psychophysics -     

Voluntary and automatic attentional control of visual working memory

Previous studies of attention-directing cues have focused largely on the effects of cuing on perceptual processes, but cuing may also influence the transfer of perceptual representations into visual working memory. In the present study, we examined this potential role of cues, using both predictive and nonpredictive cues in the context of a visual working memory task. Each trial began with a cue, followed by an array of six colored squares, a delay interval, and then a probe square presented at the location of one of the squares in the previous array. The subjects were required to indicate whether the color of the probe square was the same as the color of the square that had previously been presented at the same location. Performance on this working memory task was more accurate when the cued location was probed than when an uncued location was probed, even when the cued location was no more likely to be probed than any of the uncued locations. An additional experiment using the abrupt-onset paradigm of Yantis and Jonides (1984) yielded similar results. Thus, visual transients may automatically influence the transfer of perceptual representations into visual working memory.     

Sociomotor action control

Our actions affect the behavior of other people in predictable ways. In the present article, we describe a theoretical framework for action control in social contexts that we call sociomotor action control. This framework addresses how human agents plan and initiate movements that trigger responses from other people, and we propose that humans represent and control such actions literally in terms of the body movements they consistently evoke from observers. We review evidence for this approach and discuss commonalities and differences to related fields such as joint action, intention understanding, imitation, and interpersonal power. The sociomotor framework highlights a range of open questions pertaining to how representations of other persons’ actions are linked to one’s own motor activity, how specifically they contribute to action initiation, and how they affect the way we perceive the actions of others.     

Persistent behavior maintained by unavoidable shocks

Squirrel monkeys were trained on a multiple schedule in which 10-min periods on a continuous shock avoidance schedule, indicated by a yellow light, alternated with 10-min periods on a 1.5-min variable interval schedule of food reinforcement (VI 1.5). A white light indicated that VI 1.5 was in effect, except for the middle 2 min of the period on VI 1.5, in which a blue light appeared and terminated with the delivery of a 0.5-sec unavoidable shock. Stable response rates developed in the avoidance and VI 1.5 components. However, the highest response rates occurred in the blue, preshock stimulus. A series of experiments showed that responding in the blue stimulus persisted even when responding had been extinguished on both the VI schedule of food reinforcement and the shock avoidance schedule. Responding in the blue stimulus ceased when the blue stimulus terminated without shock or when it terminated with a response-contingent shock. Each time responding ceased, it was restored by terminating the blue stimulus with an unavoidable shock. When the blue stimulus was on throughout each session and unavoidable shocks were delivered at regular 10-min intervals, responding was well maintained. These results show that in monkeys that have been trained on a continuous avoidance schedule, unavoidable shocks can maintain responding even under conditions where responses have no programmed consequences.     

Voluntary control of pelvic frontal rotations in belly dance experts

The present study investigated how belly dance experts perform the “hip shimmy”, a complex rhythmic dance movement consisting in a voluntary oscillation of the pelvis exclusively in the frontal plane with maximised amplitude, with no movement of the upper trunk. The aims of this study were to 1) assess whether the amplitude and stability of the pelvic movement can be maximised in certain postural and frequency conditions; and 2) investigate in a 1 to 3 Hz range whether it is indeed possible to oscillate the pelvis only in the frontal plane and to dissociate this one-axis pelvic rotation from potential spontaneous upper-trunk oscillations. Nineteen belly dance experts performed this task in three frequencies and three knee bending postures. Eight joint angles were calculated using the kinematic data of 20 markers over the entire body collected with a motion capture system. Mean amplitude, frequency, and spatial and temporal variability of frontal pelvic oscillations were analysed to characterise motor performance and movement stability. Five Continuous Relative Phases (CRP) were computed to identify the modes and stability of coordination patterns. The results showed that a low posture enhances amplitude performance and that the pelvic oscillation amplitude tended to decrease at 3 Hz, although between-condition differences remained small. Temporal stability was highest at 2 Hz and significant inter-individual differences emerged at 3 Hz. CRP analysis revealed an unpreventable coupling between pelvis and upper-trunk oscillations in the frontal and transversal planes. A consistent antiphase coordination between transversal pelvis and upper-trunk may have been caused by anatomical and counter-balancing constraints. In the frontal plane, multiple stable pelvis-upper trunk patterns including inphase, out-of-phase and antiphase evolved to antiphase predominance and inphase disappearance upon reaching 3 Hz. In sum, increasing frequency highlighted the concomitance of two control phenomena: the inter-individual differentiation in performance and standardisation of the possible pelvis-upper-trunk patterns.     

Discriminated punishment: avoidable and unavoidable shock

Warning stimuli for two punishment conditions were alternated with periods of appetitive responding by rats. In either warning stimulus, the first response produced a brief shock, terminated the stimulus, and started an interval during which the baseline appetitive schedule was in effect. Not responding resulted in stimuli of random duration, which terminated with a shock under one condition and without a shock under the other. Each subject was exposed to several shock intensities, with trials for the two conditions programmed during alternate portions of the session. In general, response frequency in the warning signal for either condition decreased with increasing intensity; however, at a given intensity, responding was more frequent in the stimulus invariably terminating with shock than in the stimulus terminating without shock when no response was made. The frequency difference was greatest at intensities intermediate between those producing minimal and maximal suppression.     

Visual control of hand action

Recent investigations in normal and brain-damaged individuals have begun to identify the types of visual information used to plan and guide reaches. Binocular visual cues have been shown to be important for both movement planning and on-line guidance of hand movements, while emerging evidence suggests that dynamic visual analysis of the moving limb may provide a rich source of information for precise control of the hand in flight. Reaching movements appear to be planned to follow what is perceived to be a straight trajectory in peripersonal space. Furthermore, the process of selecting visual targets appears to influence hand trajectories, with hand movements curving away from non-target objects. This behaviour may be explained most effectively by a dynamic representation of space which is sculpted by attentional mechanisms into selected (target) and inhibited (non-target) regions. The role of attention in movement planning in individuals with attentional disorders is controversial. Patients with visual neglect have impairments of visuomotor control including reaches that, under certain conditions, are significantly more curved than those of normal individuals. The representations of space that neglect patients use to plan reaches may be distorted by impairments in the mechanisms that normally act to select target regions and inhibit non-target zones.     

The clinician-investigator: unavoidable but manageable tension

The "difference position" holds that clinical research and therapeutic medical practice are sufficiently distinct activities to require different ethical rules and principles. The "similarity position" holds instead that clinical investigators ought to be bound by the same fundamental principles that govern therapeutic medicine--specifically, a duty to provide the optimal therapeutic benefit to each patient or subject. Some defenders of the similarity position defend it because of the overlap between the role of attending physician and the role of investigator in a research trial. This overlap is maximal when the same physician occupies both roles with respect to a particular patient-subject. We address the ethical tensions inherent in that role conflict and argue that the tensions are real but manageable. The difference position provides a sound ethical framework within which to manage those tensions, while the similarity position is unsatisfactory because it seeks to deny the existence of the tensions.