Visual coding for action violates fundamental psychophysical principles

Ganel, Tzvi; Chajut, Eran; Algom, Daniel

doi:10.1016/j.cub.2008.04.052

Cited by 130 publications

(218 citation statements)

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“…The SCE, Garner, and other effects reflect the operation of the second system concerned with conscious visual experience. The dissociation was recently demonstrated with the Garner effect itself, using purely perceptual and purely motor tasks (Ganel & Goodale, 2003; see also Ganel, Chajut, & Algom, 2008).…”

Section: Discussionmentioning

confidence: 84%

The role of parity, physical size, and magnitude in numerical cognition: The SNARC effect revisited

Fitousi

Shaki

Algom

2009

Perception & Psychophysics

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Is 3 an odd or even number? The time it takes one to record a response for this simple question is affected by the relative position of the response key used to indicate parity. People respond to 3 (and to other small numbers) faster with a left-hand key, and they respond to 8 (and to other larger numbers) faster with a right-hand key, regardless of the odd-even assignment of the response keys. This spatial-numerical association of response codes (SNARC; Dehaene, Bossini, & Giraux, 1993) is notable because magnitude information is not strictly needed for deciding parity. Consequently, the presence of the SNARC effect has been taken to support the idea that the meaning of numerals (i.e., numerical magnitude) is activated in an automatic fashion when numerals are presented for view for any purpose. It is this explanation of the SNARC effect that we challenge in the present study.We employed two separate tools to test the traditional explanation of the SNARC effect. The first was the size congruity effect (SCE), a potent marker of automatic activation of semantic information with numerals. The SCE documents the influence of numerical magnitude on judgments of physical size of numerals. When the relative physical sizes of numerals in a pair are compared, people respond faster for congruent pairs (e.g., 8 2) than for incongruent pairs (e.g., 8 2; Fitousi & Algom, 2006). For singly presented numerals, people react to the large physical format of 8 faster than they do to that of 2, but the reverse holds true for 8 versus 2 (Algom, Dekel, & Pansky, 1996;Choplin & Logan, 2005). The task in studies of the SCE entails a nonsemantic attribute of digits, yet irrelevant numerical value cannot be ignored and affects task performance. Do the SCE and the SNARC effect interact in processing?In order to test the relationship between the two markers of automatic activation, in the first experiment we derived the SCE and the SNARC effect on a common set of numerals for the same group of observers. The task comprised judgments of the physical size (large, small) of numerals conveyed via alternative response key assignments (large size by the left-hand key and small size by the righthand key, or large size by the right-hand key and small size by the left-hand key). If the SNARC effect taps activation of magnitude information, it should interact with the SCE, which registers the inadvertent involvement of numerical magnitude in tasks of physical size. In particular, a larger SNARC effect is expected for congruent (large numbers in large physical formats and small numbers in small physical formats) than for incongruent (numerical and physical size conflict) number stimuli. If the SCE and the SNARC effect are found to be independent of each other, a revision People indicate the physical size or the parity status of small numbers faster by a left-hand key and those of larger numbers by a right-hand key. Because magnitude information is not required for successful performance in these tasks, the presence of a number-space association (the ...

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Section: Discussionmentioning

confidence: 84%

The role of parity, physical size, and magnitude in numerical cognition: The SNARC effect revisited

Fitousi

Shaki

Algom

2009

Perception & Psychophysics

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“…Janczyk & Kunde, 2012;Kunde, Landgraf, Paelecke, & Kiesel, 2007). Recently, however, Ganel and Goodale (2014) extended these findings and showed that for perceptual estimations Garner interference is not limited to RTs, and is expressed in the within-subject variability of the response, which has been shown to reflect response precision (Ganel, Chajut, & Algom, 2008). In particular, the final apertures of perceptual estimations were more variable in the filtering compared to the baseline condition.…”

Section: Introductionmentioning

confidence: 81%

“…Additional evidence for the dissociation in the processing styles that subserve vision-for-action and vision-forperception comes from studies that demonstrated that grasping evades the effect of Weber's law (Ganel et al, 2008;Ganel, Freud, & Meiran, 2014). According to this fundamental psychophysical law, people's ability to detect changes within a given physical dimension linearly decreases with the magnitude of this dimension (Baird & Noma, 1978).…”

Section: Introductionmentioning

confidence: 99%

Visual control of action directed toward two-dimensional objects relies on holistic processing of object shape

Freud

Ganel

2015

Psychon Bull Rev

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Visual perception relies on holistic processing of object shape. In contrast to perception, previous studies demonstrated that vision-for-action operates in a fundamentally different manner based on an analytical representation of objects. This notion was mainly supported by the absence of Garner interference for visually guided actions, compared to robust interference effects for perceptual estimations of the same objects. This study examines the nature of the representations that subserve visually guided actions toward twodimensional (2D) stimuli. Based on recent results suggesting that actions directed toward 2D objects are mediated by different underlying processes compared to normal actions, we predicted that visually guided actions toward 2D stimuli would rely on perceptually driven holistic representations of object shape. To test this idea, we asked participants to grasp 2D rectangular objects presented on a computer monitor along their width while the values of the irrelevant dimension of length were either kept constant (baseline condition) or varied between trials (filtering condition). Worse performance in the filtering blocks is labeled Garner interference, which indicates holistic processing of object shape. Unlike in previous studies that used real objects, the results showed that grasping toward 2D objects produced a significant Garner interference effect, with more variable within-subject performance in the filtering compared to the baseline blocks. This finding suggests that visually guided actions directed toward 2D targets are mediated by different computations compared to visually guided actions directed toward real objects.

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“…For example, in a size-discrimination task a participant might be asked to verbally report whether the length of a visually presented line (i.e., the comparator) differs from the length of a reference line. In this context, JNDs are defined statistically with the appropriate detection of a magnitude change based on an experimentally determined criterion [41]. Equation (1) represents Weber's Law, where W is the current amount of weight bearing, K is the Weber ratio, and ΔW is the JND…”

Section: Implicit Weight-shift Length-extension Algorithmmentioning

confidence: 99%

Development of an implicit method for directing weight shifting to the affected side in patients with stroke: a proof of concept study

et al. 2017

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Weight-shift training during stroke rehabilitation requires patient effort, potentially causing leg spasticity and anxiety, which disturb motor learning. The purpose of this study was (1) to devise an implicit guidance method for weight bearing that uses vibratory cues (and is therefore low exertion) and (2) to determine if the implicit guidance method is feasible. The first experiment included 12 healthy subjects. We conducted an experiment to produce a Weber's fraction capable of calculating a just-noticeable difference during a weight-shifting task. We then applied this Weber's fraction to a weight-shifting task in a patient with stroke. Using the implicit guidance method, the patient did not perceive an increase in weight bearing while weight shifting. Furthermore, the implicit guidance method appeared to reduce anxiety during training. This implicit guidance system warrants further investigation.

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Visual coding for action violates fundamental psychophysical principles

Cited by 130 publications

References 11 publications

The role of parity, physical size, and magnitude in numerical cognition: The SNARC effect revisited

The role of parity, physical size, and magnitude in numerical cognition: The SNARC effect revisited

Visual control of action directed toward two-dimensional objects relies on holistic processing of object shape

Development of an implicit method for directing weight shifting to the affected side in patients with stroke: a proof of concept study

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