Limits...
Action can amplify motion-induced illusory displacement.

Caniard F, Bülthoff HH, Thornton IM - Front Hum Neurosci (2015)

Bottom Line: We systematically varied deviation from midpoint at gate entry, and participants made 2AFC left/right judgments.We fitted cumulative normal functions to individual distributions and extracted the point of subjective equality (PSE) as our dependent measure.Importantly, control conditions ruled out the possibility that such amplification results from lack of motor control or differences in global trajectories as performance estimates were equivalent in the two conditions in the absence of local motion.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics Tübingen, Germany.

ABSTRACT
Local motion is known to produce strong illusory displacement in the perceived position of globally static objects. For example, if a dot-cloud or grating drifts to the left within a stationary aperture, the perceived position of the whole aperture will also be shifted to the left. Previously, we used a simple tracking task to demonstrate that active control over the global position of an object did not eliminate this form of illusion. Here, we used a new iPad task to directly compare the magnitude of illusory displacement under active and passive conditions. In the active condition, participants guided a drifting Gabor patch along a virtual slalom course by using the tilt control of an iPad. The task was to position the patch so that it entered each gate at the direct center, and we used the left/right deviations from that point as our dependent measure. In the passive condition, participants watched playback of standardized trajectories along the same course. We systematically varied deviation from midpoint at gate entry, and participants made 2AFC left/right judgments. We fitted cumulative normal functions to individual distributions and extracted the point of subjective equality (PSE) as our dependent measure. To our surprise, the magnitude of displacement was consistently larger under active than under passive conditions. Importantly, control conditions ruled out the possibility that such amplification results from lack of motor control or differences in global trajectories as performance estimates were equivalent in the two conditions in the absence of local motion. Our results suggest that the illusion penetrates multiple levels of the perception-action cycle, indicating that one important direction for the future of perceptual illusions may be to more fully explore their influence during active vision.

No MeSH data available.


Related in: MedlinePlus

The effect of motion-induced illusory displacement on perceived global position. The crosshair indicates the true global position of the Gabor patch. When the patch drifts locally to the left (left panel), the global position of the patch is also shifted to the left. When the patch drifts locally to the right (right panel), the global position of the patch is shifted to the right. In the absence of local drift (center panel) perception of the global position is veridical.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4292580&req=5

Figure 1: The effect of motion-induced illusory displacement on perceived global position. The crosshair indicates the true global position of the Gabor patch. When the patch drifts locally to the left (left panel), the global position of the patch is also shifted to the left. When the patch drifts locally to the right (right panel), the global position of the patch is shifted to the right. In the absence of local drift (center panel) perception of the global position is veridical.

Mentions: Figure 1 illustrates this basic effect. When the Gabor patch within the aperture is stationary, the perceived global position of the object is veridical. However, if the patch drifts to the left or right within the aperture, the perceived position of the whole aperture is also shifted in the same direction. While the magnitude of this type of illusory position shift is typically quite small—ranging from 2 to 15 min arc for centrally presented targets (De Valois and De Valois, 1991; Tsui et al., 2007; Kerzel et al., 2008)—it is highly robust and has proven particularly useful for exploring the level of visual processing that gives rise to MIPS (e.g., Fu et al., 2004; Arnold et al., 2007; Tsui et al., 2007; Mather and Pavan, 2009; Kosovicheva et al., 2012; Maus et al., 2013a,b).


Action can amplify motion-induced illusory displacement.

Caniard F, Bülthoff HH, Thornton IM - Front Hum Neurosci (2015)

The effect of motion-induced illusory displacement on perceived global position. The crosshair indicates the true global position of the Gabor patch. When the patch drifts locally to the left (left panel), the global position of the patch is also shifted to the left. When the patch drifts locally to the right (right panel), the global position of the patch is shifted to the right. In the absence of local drift (center panel) perception of the global position is veridical.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4292580&req=5

Figure 1: The effect of motion-induced illusory displacement on perceived global position. The crosshair indicates the true global position of the Gabor patch. When the patch drifts locally to the left (left panel), the global position of the patch is also shifted to the left. When the patch drifts locally to the right (right panel), the global position of the patch is shifted to the right. In the absence of local drift (center panel) perception of the global position is veridical.
Mentions: Figure 1 illustrates this basic effect. When the Gabor patch within the aperture is stationary, the perceived global position of the object is veridical. However, if the patch drifts to the left or right within the aperture, the perceived position of the whole aperture is also shifted in the same direction. While the magnitude of this type of illusory position shift is typically quite small—ranging from 2 to 15 min arc for centrally presented targets (De Valois and De Valois, 1991; Tsui et al., 2007; Kerzel et al., 2008)—it is highly robust and has proven particularly useful for exploring the level of visual processing that gives rise to MIPS (e.g., Fu et al., 2004; Arnold et al., 2007; Tsui et al., 2007; Mather and Pavan, 2009; Kosovicheva et al., 2012; Maus et al., 2013a,b).

Bottom Line: We systematically varied deviation from midpoint at gate entry, and participants made 2AFC left/right judgments.We fitted cumulative normal functions to individual distributions and extracted the point of subjective equality (PSE) as our dependent measure.Importantly, control conditions ruled out the possibility that such amplification results from lack of motor control or differences in global trajectories as performance estimates were equivalent in the two conditions in the absence of local motion.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Biological Cybernetics Tübingen, Germany.

ABSTRACT
Local motion is known to produce strong illusory displacement in the perceived position of globally static objects. For example, if a dot-cloud or grating drifts to the left within a stationary aperture, the perceived position of the whole aperture will also be shifted to the left. Previously, we used a simple tracking task to demonstrate that active control over the global position of an object did not eliminate this form of illusion. Here, we used a new iPad task to directly compare the magnitude of illusory displacement under active and passive conditions. In the active condition, participants guided a drifting Gabor patch along a virtual slalom course by using the tilt control of an iPad. The task was to position the patch so that it entered each gate at the direct center, and we used the left/right deviations from that point as our dependent measure. In the passive condition, participants watched playback of standardized trajectories along the same course. We systematically varied deviation from midpoint at gate entry, and participants made 2AFC left/right judgments. We fitted cumulative normal functions to individual distributions and extracted the point of subjective equality (PSE) as our dependent measure. To our surprise, the magnitude of displacement was consistently larger under active than under passive conditions. Importantly, control conditions ruled out the possibility that such amplification results from lack of motor control or differences in global trajectories as performance estimates were equivalent in the two conditions in the absence of local motion. Our results suggest that the illusion penetrates multiple levels of the perception-action cycle, indicating that one important direction for the future of perceptual illusions may be to more fully explore their influence during active vision.

No MeSH data available.


Related in: MedlinePlus