Download ppt - the role of figural context & attention in masking

the role of

figural context & attention

in masking

identification task

A. Williams and Weisstein 1978

identification task


identification task


« Consequently, as well as relying on bottom-up activation, the perceptual process may also incorporate a top-down feedbackactivity or a same-level horizontal modulation between therepresentations of context and local features. »

Breitmeyer and ögmen 2006

target-mask integration


depth connectedness



depth connectedness



depth connectedness

other gestalt factors also modulating masking- collinearity (decreased masking)- symmetry (increased masking)- similarity (increased masking)

target-only integration

Ramachandran and Cobb 1995, experiment 1





Constant SOA = 116 ms

Subjective rating of visibility:Attending squares: 1.17Attending circles: 4.08

conclusion (?)

figural context modulates the masking function ...

... but !

some researchers may have combined selective attention and grouping

others have confounded space- or location-based attention with object- or configuration-based attention

conclusion (?)

figural context modulates the masking function ...

... but !

some researchers may have combined selective attention and grouping

others have confounded space- or location-based attention with object- or configuration-based attention ...

... therefore

unclear if modulation of masking is due to grouping or space/object-based attention

space-based attentional effects

Enns and DiLollo 1997, experiment 1



masking with four-dot mask not onlydue to low-level contour interactions



masking insensitive to contour proximity at parafoveal locations



four-dot masking increased with number of targets


Enns and DiLollo 1997

conclusions

• four-dot masking cannot be explained by contour-based mechanisms commonly used to explain meta-contrast.• one explanation might be incomplete focusing of spatial attention



conclusions

• four-dot masking cannot be explained by contour-based mechanisms commonly used to explain meta-contrast.• one explanation might be incomplete focusing of spatial attention

« ... these data suggest that the need for observers to distribute their attention over all three targets, prior to the onset of the four dots, resulted in masking of even the foveated target shape. »


Tata 2002, experiment 1

masking increased with number of targets



correct attentional cue decreased masking



pop-out effect reduced masking


Tata 2002

conclusions

• results suggest that theories based on low-level processes early in visual system is insufficient to explain metacontrast masking.• visual selective attention plays an important role in metacontrast masking

object/feature-based attentional effects

inattentional blindness, is an observed phenomenon of the inability to perceive features in a visual scene when the observer is not attending to them.





more familiar, typical, or salient visual objects have higher probability of resisting IB, which leads to less masking compared to items less resistant to IB.

central attentional effects

mechanisms of masking:

• integration through common synthesis • interchannel inhibition• replacement principle

Michaels and Turvey 1979


mechanisms of masking:• camouflage masking • interruption


another role of attention:increase spatiotemporal resolution of objects presented to nonfoveal regions

masking by four dots possible because:• unattended targets are coded with low spatiotemporal

resolution • attended four-dot mask have an advantage when

competing for higher level mechanisms involved in object recognition


mechanisms of masking:• camouflage masking • interruption


another role of attention:increase spatiotemporal resolution of objects presented to nonfoveal regions

masking by four dots possible because:• unattended targets are coded with low spatiotemporal

resolution • attended four-dot mask have an advantage when

competing for higher level mechanisms involved in object recognition

Object substitution masking

conclusions

figural context and masking

• gestalt factors influence masking• target integrated in an object (2D/3D) is less masked• different temporal properties governs operation of

different gestalt factors of figural organization• target being part of larger gestalt is masked less than

when being part of a meaningless arrangement


conclusions

figural context and masking

• gestalt factors influence masking• target integrated in an object (2D/3D) is less masked• different temporal properties governs operation of

different gestalt factors of figural organization• target being part of larger gestalt is masked less than

when being part of a meaningless arrangement

attention and masking

• attending features or location of targets enhances visibility of the target

• centrally controlled attention processes mediate transfer of information from iconic levels to post-iconic levels predicts level of performance


conclusions

both figural context and attention affects visibility of a target, but this is a general feature of attention/figural context when studied in a variety of other experimental paradigms


conclusions

both figural context and attention affects visibility of a target, but this is a general feature of attention/figural context when studied in a variety of other experimental paradigms

« Thus both top-down influences on backward masking can be viewed simply as modulators of masking analogous to the bottom-up modulatory effects produced by varying certain physical parameters of the target and mask stimuli »


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