Attention orienting near the hand following performed and imagined actions.

Recent studies have documented that the hand's ability to perform actions affects the visual processing and attention for objects near the hand, suggesting that actions may have specific effects on visual orienting. However, most research on the relation between spatial attention and action focuses on actions as responses to visual attention manipulations. The current study examines visual attention immediately following an executed or imagined action. A modified spatial cuing paradigm tested whether a brief, lateralized hand-pinch performed by a visually hidden hand near the target location, facilitated or inhibited subsequent visual target detection. Conditions in which hand-pinches were fully executed (action) were compared to ones with no hand-pinch (inaction) in Experiment 1 and imagined pinches (imagine) in Experiment 2. Results from Experiment 1 indicated that performed hand pinches facilitated rather than inhibited subsequent detection responses to targets appearing near the pinch, but target detection was not affected by inaction. In Experiment 2, both action and imagined action conditions cued attention and facilitated responses, but along differing time courses. These results highlight the ongoing nature of visual attention and demonstrate how it is deployed to locations even following actions.

Top-down influences mediate hand bias in spatial attention.

Spatial attention can be biased to locations near the hand. Some studies have found facilitated processing of targets appearing within hand-grasping space. In this study, we investigated how changing top-down task priorities alters hand bias during visual processing. In Experiment 1, we used a covert orienting paradigm with nonpredictive cues and emphasized the location of the hand relative to the target. Hands or visual anchors (boards) were placed next to potential target locations, and responses were made with the contralateral hand. Results indicated a hand-specific processing bias: Hand location, but not board location, speeded responses to targets near the hand. This pattern of results replicated previous studies using covert orienting paradigms with highly predictive cues. In Experiment 2, we used the same basic paradigm but emphasized the location of the response hand. Results now showed speeded responses to targets near response locations. Together these experiments demonstrated that top-down instructional sets (i.e., what is considered to be most relevant to task performance) can change the processing priority of hand location by influencing the strength of top-down, as compared with bottom-up, inputs competing for attention resources.

Implied body action directs spatial attention.

Research confirms that the body influences perception, but little is known about the embodiment of attention. We investigated whether the implied actions of others direct spatial attention, using a lateralized covert-orienting task with nonpredictive central cues depicting static, right/left-facing bodies poised in midaction. Validity effects (decreased response times for validly compared with invalidly cued trials) indicated orienting in the direction of the implied action. In Experiment 1, we compared action (running, throwing) with nonaction (standing) cues. Only the action cues produced validity effects, suggesting that implied action directs attention. The action cues produced faster responses overall, suggesting that action cues prime motor responses. In Experiment 2, we determined whether action cues shifted attention in a specific direction rather than to a general side of space: Two cues had similar action speed and motor effort but differed in implied direction (jumping, vertical; throwing, horizontal). Validity effects were found only for the throw cues for which the implied motion direction was consistent with lateralized target locations. In Experiment 3, we compared block-like stimuli to the throwing action stimuli to examine whether lower level perceptual information could account for the attention effects alone. Validity effects were found only for the human-action stimuli. Overall, the results suggest that predictive simulations of action shift attention in action-consistent directions.

Grab it! Biased attention in functional hand and tool space.

This study explored whether functional properties of the hand and tools influence the allocation of spatial attention. In four experiments that used a visual-orienting paradigm with predictable lateral cues, hands or tools were placed near potential target locations. Results showed that targets appearing in the hand's grasping space (i.e., near the palm) and the rake's raking space (i.e., near the prongs) produced faster responses than did targets appearing to the back of the hand, to the back of the rake, or near the forearm. Validity effects were found regardless of condition in all experiments, but they did not interact with the target-in-grasping/raking-space bias. Thus, the topology of the facilitated space around the hand is, in part, defined by the hand's grasping function and can be flexibly extended by functional experience using a tool. These findings are consistent with the operation of bimodal neurons, and this embodied component is incorporated into a neurally based model of spatial attention.

Walking reveals trunk orientation bias for visual attention.

Our trunks influence where we perform actions in space. Thus, trunk direction may define a region of spacethat is accorded special treatment by the attention system. We investigated conditions under which a trunk orientation bias for attention might be relevant for healthy adults. Three experiments compared visual detection performance for participants standing and walking on a treadmill. Together, the experiments disambiguate the relative contributions of motor activity, motor load, and cognitive load on trunk orientation biases. In Experiment 1, trunk orientation biases (i.e., faster target detection for targets in front of the body midline) were observed in both forward and sideways walking conditions, but not in standing conditions. In Experiment 2, we ruled out the notion that the trunk orientation bias arose from increased motor activity; in fact, the bias was greatest when participants walked at an unusually slow pace. In Experiment 3, we directly compared motor load with cognitive load in a dual-task paradigm; cognitive load influenced overall performance speed, but only motor load produced trunk orientationbias. These results suggest that a trunk orientation bias emerges during walking and motor load conditions.

A neuropsychological examination of the underlying deficit in attention deficit hyperactivity disorder: frontal lobe versus right parietal lobe theories.

A neuropsychological approach was used to examine the frontal lobe and right parietal lobe theories of attention deficit hyperactivity disorder (ADHD). Considerable attempts were made to select as pure a group of ADHD boys as possible. The performance of 10-14-year-old ADHD boys (n = 22), both on and off stimulant medication, was compared with the performance of non-ADHD control boys (n = 22) on tasks purported to assess frontal lobe functioning (Stopping Task, Antisaccade Task, Tower of Hanoi) and right parietal lobe functioning (Visual-Spatial Cuing Task, Turning Task, Spatial Relations). Three important findings emerged: (a) unmedicated ADHD boys exhibited performance deficits on tasks in both frontal and parietal domains compared with control boys, (b) unmedicated ADHD boys appeared to be more severely impaired on the frontal tasks than on the parietal tasks, and (c) medicated ADHD boys performed better in both task domains compared with unmedicated ADHD boys. Several alternative interpretations of the results are discussed.