Davood G. Gozli

Hand position alters vision by biasing processing through different visual pathways

The present study investigated the mechanisms responsible for the difference between visual processing of stimuli near and far from the observers hands. The idea that objects near the hands are immediate candidates for action led us to hypothesize that vision near the hands would be biased toward the action-oriented magnocellular visual pathway that supports processing with high temporal resolution but low spatial resolution. Conversely, objects away from the hands are not immediate candidates for action and, therefore, would benefit from a bias toward the perception-oriented parvocellular visual pathway that supports processing with high spatial resolution but low temporal resolution. We tested this hypothesis based on the psychophysical characteristics of the two pathways. Namely, we presented subjects with two tasks: a temporal-gap detection task which required the high temporal acuity of the magnocellular pathway and a spatial-gap detection task that required the spatial acuity of the parvocellular pathway. Consistent with our prediction, we found better performance on the temporal-gap detection task and worse performance on the spatial-gap detection task when stimuli were presented near the hands compared to when they were far from the hands. These findings suggest that altered visual processing near the hands may be due to changes in the contribution of the two visual pathways.

Reduced Temporal Fusion in Near-Hand Space

Object-substitution masking (OSM) is thought to reflect a failure of object individuation. That is, a briefly presented target surrounded by four dots is perceptually fused with the four-dot mask when the mask is visible after the target has disappeared, thereby obscuring the visibility of the target. If OSM depends on the inability to temporally segregate objects, then increasing the temporal precision of the visual system should reduce OSM. In the study reported here, we manipulated temporal precision by varying the proximity of participants’ hands to visual stimuli, because stimuli in near-hand space have been found to enjoy enhanced attentional processing, and attention is known to speed visual processing. Hand placement was indeed found to affect OSM: Placing participants’ hands near the visual stimuli reduced the magnitude of the masking. This finding demonstrates that object individuation can be facilitated by increasing the temporal resolution of vision via increasing the proximity of visual stimuli to the hands.

The cost and benefit of implicit spatial cues for visual attention.

Processing concepts with implicit spatial meaning or metaphorical spatial association has been shown to engage visuospatial mechanisms, causing either facilitation or interference with concurrent visual processing at locations compatible with the concepts. It is, however, unclear when interference or facilitation should be expected. It is possible that both effects result from the same processes that interact differently with different visual tasks (e.g., facilitating detection and interfering with discrimination). Alternatively, the 2 effects might represent different temporal stages of the same kind of processes, which can interfere with a congruent visual task at early stages but can cause facilitation at later stages. Finally, the 2 effects might be due to the differences in the underlying representations of concepts, particularly the differences between abstract and concrete concepts. Results of the present study are consistent with the view that interference and facilitation represent 2 temporal stages of the same kind of processes. In addition, the results reveal the unexpected importance of using multiple conceptual categories (as opposed to a single category) in observing the time course of the effects.

Valence and vertical space: Saccade trajectory deviations reveal metaphorical spatial activation

Concepts of positive and negative valence are metaphorically structured in space (e.g., happy is up, sad is down). In fact, coupling a conceptual task (e.g., evaluating words as positive or negative) with a visuospatial task (e.g., identifying stimuli above or below fixation) often gives rise to metaphorical congruency effects. For instance, after reading a positive concept, visual target processing is facilitated above fixation. However, it is possible that tasks requiring upwards and downwards attentional orienting artificially strengthen the link between vertical space and semantic valence. For this reason, in the present study the vertical axis was uncoupled from the response axis. Participants made eye movements along the horizontal axis after reading positive or negative affect words, while their saccade movement trajectories were recorded. Based on previous research on saccade trajectory deviation, we predicted that fast saccade trajectories curve towards the salient segment of space, whereas slow saccade trajectories would curve away from the salient segment. Examining saccadic trajectories revealed a pattern of deviations along the vertical axis consistent with the metaphorical congruency account, although this pattern was mainly driven by positive concepts. These results suggest that semantic processing of valence can automatically recruit spatial features along the vertical axis.

The effect of action video game playing on sensorimotor learning: Evidence from a movement tracking task.

Research on the impact of action video game playing has revealed performance advantages on a wide range of perceptual and cognitive tasks. It is not known, however, if playing such games confers similar advantages in sensorimotor learning. To address this issue, the present study used a manual motion-tracking task that allowed for a sensitive measure of both accuracy and improvement over time. When the target motion pattern was consistent over trials, gamers improved with a faster rate and eventually outperformed non-gamers. Performance between the two groups, however, did not differ initially. When the target motion was inconsistent, changing on every trial, results revealed no difference between gamers and non-gamers. Together, our findings suggest that video game playing confers no reliable benefit in sensorimotor control, but it does enhance sensorimotor learning, enabling superior performance in tasks with consistent and predictable structure.

Reduced visual feature binding in the near-hand space.

Growing evidence suggests that visual information is processed differently in the near-hand space, relative to the space far from the hands. To account for the existing literature, we recently proposed that the costs and benefits of hand proximity may be due to differential contributions of the action-oriented magnocellular (M) and the perception-oriented parvocellular (P) pathways. Evidence suggests that, relative to the space far from the hands, in near-hand space the contribution of the M pathway increases while the contribution of the P pathway decreases. The present study tested an important consequence of this account for visual representation. Given the P pathway’s role in feeding regions in which visual representations of unified objects (with bound features) are formed, we predicted that hand proximity would reduce feature binding. Consistent with this prediction, two experiments revealed signs of reduced feature binding in the near-hand space, relative to the far-hand space. We propose that the higher contribution of the M pathway, along with the reduced contribution of the P pathway, shifts visual perception away from an object-based perceptual mode toward a feature-based mode. These results are discussed in light of the distinction between action-oriented and perception-oriented vision.

A touchy subject: advancing the modulated visual pathways account of altered vision near the hand

Abstract A growing body of evidence demonstrates that human vision operates differently in the space near and on the hands; for example, early findings in this literature reported that rapid onsets are detected faster near the hands, and that objects are searched more thoroughly. These and many other effects were attributed to enhanced attention via the recruitment of bimodal visual-tactile neurons representing the hand and near-hand space. However, recent research supports an alternative account: stimuli near the hands are preferentially processed by the action-oriented magnocellular visual pathway at the expense of processing in the parvocellular pathway. This Modulated Visual Pathways (MVP) account of altered vision near the hands describes a hand position-dependent trade-off between the two main retinal-cortical visual pathways between the eye and brain. The MVP account explains past findings and makes new predictions regarding near-hand vision supported by new research.

Ideomotor perception modulates visuospatial cueing

The ideomotor theory of action posits that the cognitive representation of an action includes the learned perceptual effects of the action. Support for this theory has come from studies demonstrating how perceptual features that match the outcome of a response can facilitate selection of that response. We investigated another, complementary implication of ideomotor theory: would a bias toward selecting a response result in a perceptual bias toward the known effect of the response? In other words, would an action tendency direct attention to the anticipated perceptual features? Through an initial acquisition phase, participants learned that two possible responses (left/right keypress) consistently produced two distinct colors. Next, in a test phase, we manipulated response bias at the beginning of each trial, using an uninformative spatial prime presented at the left or right periphery. We then examined the extent to which color transients that either matched or mismatched the induced response bias can orient participants’ visual attention. Results revealed a perceptual bias toward the color effect of the primed response, manifested in a stronger visual orienting toward this color. Thus, biasing response selection can bias perception. These findings extend the scope of the ideomotor theory to visual perceptual processes.

Seeing while acting: Hand movements can modulate attentional capture by motion onset

The onset of new motion has been shown to be a very robust cause of attentional capture, generating a processing advantage for the location of motion onset regardless of the observer’s concurrent goal. The present study, motivated by the common-coding account of action and perception, examined whether the effect of motion onset on visual attention can be modulated by the observer’s mode of action. Specifically, the common-coding account predicts that preparing an action can render the features that are used in the action plan less available for visual processes. Consistent with this hypothesis, in Experiment 1 the magnitude of attentional capture caused by a single motion onset was reduced when this motion was similar to the observer’s response (i.e., along the same axis). Similarly, in Experiment 2 the onset of a response-different motion gained a processing advantage over the response-similar motion onset when the two were presented simultaneously. Since both types of motion were present in every trial, the results of Experiment 2 suggest that response similarity affected visual-attentional processes rather than motor processes. Together, these results suggest that the processes of attentional prioritization caused by motion onset can be modulated by the observer’s concurrent action.

Acting and anticipating: impact of outcome-compatible distractor depends on response selection efficiency

Action selection is thought to involve selection of the actions sensory outcomes. This notion is supported when encountering a distractor that resembles a learned response-outcome biases response selection. Some evidence, however, suggests that a larger contribution of stimulus-based response selection leaves little role for outcome-based selection, especially in forced-choice tasks with easily identifiable target stimuli. In the present study, we asked whether the contribution of outcome-based selection depends on the ease and efficiency of stimulus-based selection. If so, then efficient stimulus-based response selection should reduce the impact of an irrelevant distractor that resemble a response-outcome. We manipulated efficiency of stimulus-based selection by varying the spatial relationship between stimulus and response (Experiment 1) and by varying stimulus discriminability (Experiments 2). We hypothesized that with efficient stimulus-based selection, outcome-based processes will play a weaker role in response selection, and performance will be less susceptible to outcome-compatible or -incompatible distractors. By contrast, when stimulus-based selection is relatively inefficient, outcome-based processes will play a stronger role in response selection, and performance should be more susceptible to outcome-compatible or -incompatible distractors. Confirming our predictions, our results showed stronger impact of the distractors when stimulus-based response selection was relatively inefficient. Finally, results of a control experiment (Experiment 3) suggested that learning the consistent response-outcome mapping is necessary for obtaining the effect of these distractors. We conclude that outcome-based processes do contribute to response selection in forced-choice tasks, and that this contribution varies with the efficiency of stimulus-based response selection. (PsycINFO Database Record