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Active gaze control improves optic flow-based segmentation and steering.

Raudies F, Mingolla E, Neumann H - PLoS ONE (2012)

Bottom Line: To support our suggestion we derive an analytical model that shows: Tangentially fixating the outer surface of an obstacle leads to strong flow discontinuities that can be used for flow-based segmentation.Fixation of the target center while gaze and heading are locked without head-, body-, or eye-rotations gives rise to a symmetric expansion flow with its center at the point being approached, which facilitates steering toward a target.We conclude that gaze control incorporates ecological constraints to improve the robustness of steering and collision avoidance by actively generating flows appropriate to solve the task.

View Article: PubMed Central - PubMed

Affiliation: Center of Excellence for Learning in Education, Science, and Technology, Boston University, Boston, Massachusetts, United States of America. fraudies@bu.edu

ABSTRACT
An observer traversing an environment actively relocates gaze to fixate objects. Evidence suggests that gaze is frequently directed toward the center of an object considered as target but more likely toward the edges of an object that appears as an obstacle. We suggest that this difference in gaze might be motivated by specific patterns of optic flow that are generated by either fixating the center or edge of an object. To support our suggestion we derive an analytical model that shows: Tangentially fixating the outer surface of an obstacle leads to strong flow discontinuities that can be used for flow-based segmentation. Fixation of the target center while gaze and heading are locked without head-, body-, or eye-rotations gives rise to a symmetric expansion flow with its center at the point being approached, which facilitates steering toward a target. We conclude that gaze control incorporates ecological constraints to improve the robustness of steering and collision avoidance by actively generating flows appropriate to solve the task.

Show MeSH
Illustration of two tasks that generate two strategies for gaze control.a) If humans approach a target they fixate the center and align heading with gaze. b) To avoid an obstacle the outer edge is fixated and gaze points to a direction that is different from the direction of heading. This outer edge is an apical edge. These two sketches are based on the findings reported by Rothkopf & Ballard [14] and Fajen & Warren [15]. c) These strategies are embedded in a larger set of possible control strategies that depend on gaze and heading, the point of fixation, and the role of the faced object to be either target or obstacle. The control strategies from a) and b) are used by humans. Our derived model provides a flow-based analysis of all four possible strategies that does not include the detection of an object to be target or obstacle, e.g. by a color cue as in the experiment.
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pone-0038446-g001: Illustration of two tasks that generate two strategies for gaze control.a) If humans approach a target they fixate the center and align heading with gaze. b) To avoid an obstacle the outer edge is fixated and gaze points to a direction that is different from the direction of heading. This outer edge is an apical edge. These two sketches are based on the findings reported by Rothkopf & Ballard [14] and Fajen & Warren [15]. c) These strategies are embedded in a larger set of possible control strategies that depend on gaze and heading, the point of fixation, and the role of the faced object to be either target or obstacle. The control strategies from a) and b) are used by humans. Our derived model provides a flow-based analysis of all four possible strategies that does not include the detection of an object to be target or obstacle, e.g. by a color cue as in the experiment.

Mentions: Eye-tracking data shows that active gaze control is used by humans. Gaze is actively controlled in ordinary daily tasks [11], e.g. the making of a cup of tea [12] or steering a vehicle on the road during driving [13]. When preparing a peanut butter and jelly sandwich, humans deploy an orchestrated sequence of eye-movements that are astonishingly similar between participants when given the same abstract instruction [11]. Eye-tracking data shows that humans are actively selecting gaze points that are related to the current task [11], [12]. During a visual navigation task humans fixate the center of targets while they prefer to fixate the edge of obstacles [14]. An illustration is shown in Figure 1. What generates this task-dependent difference in gaze behavior? Why do we not use one of the other possible control strategies? For instance we could fixate the center of an obstacle or the edge of a target, as shown in Figure 1c.


Active gaze control improves optic flow-based segmentation and steering.

Raudies F, Mingolla E, Neumann H - PLoS ONE (2012)

Illustration of two tasks that generate two strategies for gaze control.a) If humans approach a target they fixate the center and align heading with gaze. b) To avoid an obstacle the outer edge is fixated and gaze points to a direction that is different from the direction of heading. This outer edge is an apical edge. These two sketches are based on the findings reported by Rothkopf & Ballard [14] and Fajen & Warren [15]. c) These strategies are embedded in a larger set of possible control strategies that depend on gaze and heading, the point of fixation, and the role of the faced object to be either target or obstacle. The control strategies from a) and b) are used by humans. Our derived model provides a flow-based analysis of all four possible strategies that does not include the detection of an object to be target or obstacle, e.g. by a color cue as in the experiment.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375264&req=5

pone-0038446-g001: Illustration of two tasks that generate two strategies for gaze control.a) If humans approach a target they fixate the center and align heading with gaze. b) To avoid an obstacle the outer edge is fixated and gaze points to a direction that is different from the direction of heading. This outer edge is an apical edge. These two sketches are based on the findings reported by Rothkopf & Ballard [14] and Fajen & Warren [15]. c) These strategies are embedded in a larger set of possible control strategies that depend on gaze and heading, the point of fixation, and the role of the faced object to be either target or obstacle. The control strategies from a) and b) are used by humans. Our derived model provides a flow-based analysis of all four possible strategies that does not include the detection of an object to be target or obstacle, e.g. by a color cue as in the experiment.
Mentions: Eye-tracking data shows that active gaze control is used by humans. Gaze is actively controlled in ordinary daily tasks [11], e.g. the making of a cup of tea [12] or steering a vehicle on the road during driving [13]. When preparing a peanut butter and jelly sandwich, humans deploy an orchestrated sequence of eye-movements that are astonishingly similar between participants when given the same abstract instruction [11]. Eye-tracking data shows that humans are actively selecting gaze points that are related to the current task [11], [12]. During a visual navigation task humans fixate the center of targets while they prefer to fixate the edge of obstacles [14]. An illustration is shown in Figure 1. What generates this task-dependent difference in gaze behavior? Why do we not use one of the other possible control strategies? For instance we could fixate the center of an obstacle or the edge of a target, as shown in Figure 1c.

Bottom Line: To support our suggestion we derive an analytical model that shows: Tangentially fixating the outer surface of an obstacle leads to strong flow discontinuities that can be used for flow-based segmentation.Fixation of the target center while gaze and heading are locked without head-, body-, or eye-rotations gives rise to a symmetric expansion flow with its center at the point being approached, which facilitates steering toward a target.We conclude that gaze control incorporates ecological constraints to improve the robustness of steering and collision avoidance by actively generating flows appropriate to solve the task.

View Article: PubMed Central - PubMed

Affiliation: Center of Excellence for Learning in Education, Science, and Technology, Boston University, Boston, Massachusetts, United States of America. fraudies@bu.edu

ABSTRACT
An observer traversing an environment actively relocates gaze to fixate objects. Evidence suggests that gaze is frequently directed toward the center of an object considered as target but more likely toward the edges of an object that appears as an obstacle. We suggest that this difference in gaze might be motivated by specific patterns of optic flow that are generated by either fixating the center or edge of an object. To support our suggestion we derive an analytical model that shows: Tangentially fixating the outer surface of an obstacle leads to strong flow discontinuities that can be used for flow-based segmentation. Fixation of the target center while gaze and heading are locked without head-, body-, or eye-rotations gives rise to a symmetric expansion flow with its center at the point being approached, which facilitates steering toward a target. We conclude that gaze control incorporates ecological constraints to improve the robustness of steering and collision avoidance by actively generating flows appropriate to solve the task.

Show MeSH