A Double Dissociation Between Action and Perception in the Context of Visual Illusions

Ganel, Tzvi; Tanzer, Michal; Goodale, Melvyn A.

doi:10.1111/j.1467-9280.2008.02071.x

Cited by 127 publications

(101 citation statements)

References 22 publications

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“…A few previous studies have documented oppositely directed perceptions and actions that do not arise from opposite illusions, but rather from the experimental conditions chosen for comparison (Ganel et al 2008;Grandy and Westwood 2006). In one such study (Grandy and Westwood 2006), grip forces associated with alternate rapid lifting of a small, lighter object (2.7 N) and a large, heavier one (3.2 N) from a table were measured.…”

Section: Opposite Illusions Versus Opposite Behaviormentioning

confidence: 99%

Bayesian and “Anti-Bayesian” Biases in Sensory Integration for Action and Perception in the Size–Weight Illusion

Brayanov

Smith

2010

Journal of Neurophysiology

101

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Brayanov JB, Smith MA. Bayesian and "anti-Bayesian" biases in sensory integration for action and perception in the size-weight illusion. J Neurophysiol 103: 1518 -1531, 2010. First published January 20, 2010 doi:10.1152/jn.00814.2009. Which is heavier: a pound of lead or a pound of feathers? This classic trick question belies a simple but surprising truth: when lifted, the pound of lead feels heavier-a phenomenon known as the size-weight illusion. To estimate the weight of an object, our CNS combines two imperfect sources of information: a prior expectation, based on the object's appearance, and direct sensory information from lifting it. Bayes' theorem (or Bayes' law) defines the statistically optimal way to combine multiple information sources for maximally accurate estimation. Here we asked whether the mechanisms for combining these information sources produce statistically optimal weight estimates for both perceptions and actions. We first studied the ability of subjects to hold one hand steady when the other removed an object from it, under conditions in which sensory information about the object's weight sometimes conflicted with prior expectations based on its size. Since the ability to steady the supporting hand depends on the generation of a motor command that accounts for lift timing and object weight, hand motion can be used to gauge biases in weight estimation by the motor system. We found that these motor system weight estimates reflected the integration of prior expectations with real-time proprioceptive information in a Bayesian, statistically optimal fashion that discounted unexpected sensory information. This produces a motor sizeweight illusion that consistently biases weight estimates toward prior expectations. In contrast, when subjects compared the weights of two objects, their perceptions defied Bayes' law, exaggerating the value of unexpected sensory information. This produces a perceptual size-weight illusion that biases weight perceptions away from prior expectations. We term this effect "anti-Bayesian" because the bias is opposite that seen in Bayesian integration. Our findings suggest that two fundamentally different strategies for the integration of prior expectations with sensory information coexist in the nervous system for weight estimation.

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Section: Opposite Illusions Versus Opposite Behaviormentioning

confidence: 99%

Bayesian and “Anti-Bayesian” Biases in Sensory Integration for Action and Perception in the Size–Weight Illusion

Brayanov

Smith

2010

Journal of Neurophysiology

101

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“…Certain objects such as tools, for example, demand that we grasp Figure 3. The Ponzo illusion experiment by Ganel et al [47]. The top diagram shows the experimental display.…”

Section: Interactions Between the Two Streamsmentioning

confidence: 99%

“…As it turns out, a more recent study has been able to demonstrate a double dissociation between perception and action. Ganel et al [47] rspb.royalsocietypublishing.org Proc. R. Soc.…”

Section: Evidence For a Perception-action Dissociation From Behaviourmentioning

confidence: 99%

How (and why) the visual control of action differs from visual perception

Goodale

2014

Proc. R. Soc. B.

Self Cite

131

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Vision not only provides us with detailed knowledge of the world beyond our bodies, but it also guides our actions with respect to objects and events in that world. The computations required for vision-for-perception are quite different from those required for vision-for-action. The former uses relational metrics and scene-based frames of reference while the latter uses absolute metrics and effector-based frames of reference. These competing demands on vision have shaped the organization of the visual pathways in the primate brain, particularly within the visual areas of the cerebral cortex. The ventral 'perceptual' stream, projecting from early visual areas to inferior temporal cortex, helps to construct the rich and detailed visual representations of the world that allow us to identify objects and events, attach meaning and significance to them and establish their causal relations. By contrast, the dorsal 'action' stream, projecting from early visual areas to the posterior parietal cortex, plays a critical role in the real-time control of action, transforming information about the location and disposition of goal objects into the coordinate frames of the effectors being used to perform the action. The idea of two visual systems in a single brain might seem initially counterintuitive. Our visual experience of the world is so compelling that it is hard to believe that some other quite independent visual signal-one that we are unaware of-is guiding our movements. But evidence from a broad range of studies from neuropsychology to neuroimaging has shown that the visual signals that give us our experience of objects and events in the world are not the same ones that control our actions.

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“…Thus, both tasks were performed in a visual Bclosedl oop. d The experimental protocol was designed (1) to parse variance in the response into the effect of the real difference in target length and the magnitude of an illusory bias induced by the Ponzo display, and (2) to allow us to operationalize the timing for each of these effects by binning adjacent groups of four consecutive trials for temporal analysis targets immediately after each estimate (e.g., Ganel, Tanzer, & Goodale, 2008).…”

Section: Experimental Designmentioning

confidence: 99%

Rapid decrement in the effects of the Ponzo display dissociates action and perception

et al. 2015

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It has been demonstrated that pictorial illusions have a smaller influence on grasping than they do on perceptual judgments. Yet to date this work has not considered the reduced influence of an illusion as it is measured repeatedly. Here we studied this decrement in the context of a Ponzo illusion to further characterize the dissociation between vision for perception and for action. Participants first manually estimated the lengths of single targets in a Ponzo display with their thumb and index finger, then actually grasped these targets in another series of trials, and then manually estimated the target lengths again in a final set of trials. The results showed that although the perceptual estimates and grasp apertures were equally sensitive to real differences in target length on the initial trials, only the perceptual estimates remained biased by the illusion over repeated measurements. In contrast, the illusion's effect on the grasps decreased rapidly, vanishing entirely after only a few trials. Interestingly, a closer examination of the grasp data revealed that this initial effect was driven largely by undersizing the grip aperture for the display configuration in which the target was positioned between the diverging background lines (i.e., when the targets appeared to be shorter than they really were). This asymmetry between grasping apparently shorter and longer targets suggests that the sensorimotor system may initially treat the edges of the configuration as obstacles to be avoided. This finding highlights the sensorimotor system's ability to rapidly update motor programs through error feedback, manifesting as an immunity to the effects of illusion displays even after only a few trials.

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A Double Dissociation Between Action and Perception in the Context of Visual Illusions

Cited by 127 publications

References 22 publications

Bayesian and “Anti-Bayesian” Biases in Sensory Integration for Action and Perception in the Size–Weight Illusion

Bayesian and “Anti-Bayesian” Biases in Sensory Integration for Action and Perception in the Size–Weight Illusion

How (and why) the visual control of action differs from visual perception

Rapid decrement in the effects of the Ponzo display dissociates action and perception

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