Object-based inhibition of return in static displays

After attention has been oriented to a location, inhibition mechanisms prevent the return of attention shortly afterward. This inhibition can be associated with an object in such a way that after cuing attention to the object, inhibition can move with the object to a new location. Recent research has noted that the object-based inhibition of return effect in moving displays is much smaller than the effect observed in static displays, and hence may be of little functional utility. However, we demonstrate that, on the contrary, the large effects observed in static displays are produced precisely because of the existence of object-based frames, which can be additive with location-based frames of reference.     

Fathering and Early Onset Conduct Problems: Positive and Negative Parenting, Father–Son Attachment, and the Marital Context

Research literature linking negative and positive aspects of the father–child relationship with early onset conduct problems is reviewed. Evidence from the Preschool Families Project, a longitudinal study of clinic-referred preschool boys at risk for conduct disorder, is presented, including previously unpublished data on father–child attachment. Both negative (e.g., harsh, angry, and physically punitive) and positive (involvement, warmth, and secure attachment) dimensions of fathering, as well as aspects of the marital relationship, appear to be associated with the emergence of early onset conduct problems.     

Visual attention in infants with perinatal brain damage: Evidence of the importance of anterior lesions

Shifts of visual attention can be studied in adults and infants by cueing responses to a particular spatial location. Earlier studies have shown that by seven months of age normal infants show a similar pattern of facilitation and inhibition to a cued spatial location as adults. In this study we report data from infants with perinatal lesions that include or exclude the left anterior quadrant. Results indicate that infants with left anterior lesions do not show facilitation to a cued spatial location in this task. In contrast, infants with posterior lesions showed the same pattern of performance as healthy subjects. While these findings differ from those obtained with adults, they are consistent with previous studies of children with perinatal lesions, and with findings from ERP studies with normal infants.     

Visual inertia of rotating 3-D objects

Five experiments were designed to determine whether a rotating, transparent 3-D cloud of dots (simulated sphere) could influence the perceived direction of rotation of a subsequent sphere. Experiment 1 established conditions under which the direction of rotation of a virtual sphere was perceived unambiguously. When a near-far luminance difference and perspective depth cues were present, observers consistently saw the sphere rotate in the intended direction. In Experiment 2, a near-far luminance difference was used to create an unambiguous rotation sequence that was followed by a directionally ambiguous rotation sequence that lacked both the near-far luminance cue and the perspective cue. Observers consistently saw the second sequence as rotating in the same direction as the first, indicating the presence of 3-D visual inertia. Experiment 3 showed that 3-D visual inertia was sufficiently powerful to bias the perceived direction of a rotation sequence made unambiguous by a near-far luminance cue. Experiment 5 showed that 3-D visual inertia could be obtained using an occlusion depth cue to create an unambiguous inertia-inducing sequence. Finally, Experiments 2, 4, and 5 all revealed a fast-decay phase of inertia that lasted for approximately 800 msec, followed by an asymptotic phase that lasted for periods as long as 1,600 msec. The implications of these findings are examined with respect to motion mechanisms of 3-D visual inertia.     

A Search for the Optimal Stimulus

How do stimulus size and item number relate to the magnitude and direction of error on center estimation and line cancellation tests? How might this relationship inform theories concerning spatial neglect? These questions were addressed by testing twenty patients with right hemisphere lesions, eleven with left hemisphere lesions and eleven normal control subjects on multiple versions of center estimation and line cancellation tests. Patients who made large errors on these tests also demonstrated an optimal or pivotal stimulus value, i.e., a particular size center estimation test or number of lines on cancellation that either minimized error magnitude relative to other size stimuli (optimal) or marked the boundary between normal and abnormal performance (pivotal). Patients with right hemisphere lesions made increasingly greater errors on the center estimation test as stimuli were both larger and smaller than the optimal value, whereas those with left hemisphere lesions made greater errors as stimuli were smaller than a pivotal value. In normal subjects, the direction of errors on center estimation stimuli shifted from the right of true center to the left as stimuli decreased in size (i.e., the crossover effect). Right hemisphere lesions exaggerated this effect, whereas left hemisphere lesions diminished and possibly reversed the direction of crossover. Error direction did not change as a function of stimulus value on cancellation tests. The demonstration of optimal and pivotal stimulus values indicates that performances on center estimation and cancellation tests in neglect are only relative to the stimuli used. In light of other studies, our findings indicate that patients with spatial neglect grossly overestimate the size of small stimuli and underestimate the size of large stimuli, that crossover represents an “apparent” shift in error direction that actually results from normally occurring errors in size perception, and that the left hemisphere is specialized for one aspect of size estimation, whereas the right performs dual roles.     

A study of a bimanual synergy associated with holding an object

The task of supporting an object with one or two hands was used to test the applicability of the notion of synergy. Subjects sat with their dominant forearm supported up to the wrist while holding a cylindrical “cup” between their thumb and fingers. Force transducers recorded the grip force applied normal to the cup's side by the thumb and the force applied normal to the cup bottom. On different series, a supporting force was added to and released from the bottom of the cup by the subject's non-dominant hand or by the experimenter. As predicted, the results indicated feedforward adjustments of the grip force, and of the EMGs, and significant correlations between grip force and supporting force when they were produced by two hands of one person, and the lack of such closely tied changes when the two forces were produced by two different persons. In the latter case, different subjects could demonstrate grip force changes in different directions. The findings suggest that grip force adjustments represented peripheral patterns of a single central process (a single synergy) rather than being separately controlled focal and postural components of the action.PsycINFO classification: 2330