1. the role of figural context & attention in masking

2. identification task
A. Williams and Weisstein 1978

3. identification task
A. Williams and Weisstein 1978

4. identification task
A. Williams and Weisstein 1978
« Consequently, as well as relying on bottom-up activation,
the perceptual process may also incorporate a top-down feedback
activity or a same-level horizontal modulation between the
representations of context and local features. »
Breitmeyer and ögmen 2006

5. target-mask integration
depth connectedness
A. Williams and Weisstein 1981

6. target-mask integration
depth connectedness
A. Williams and Weisstein 1981

7. target-mask integration
depth connectedness
other gestalt factors also modulating masking
- collinearity (decreased masking)
- symmetry (increased masking)
- similarity (increased masking)
A. Williams and Weisstein 1981

8. target-only integration
Ramachandran and Cobb 1995, experiment 1

9. target-only integration
Ramachandran and Cobb 1995, experiment 1

10. target-only integration
Constant SOA = 116 ms
Subjective rating of visibility:
Attending squares: 1.17
Attending circles: 4.08
Ramachandran and Cobb 1995, experiment 2

11. 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

12. 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

13. space-based attentional effects
Enns and DiLollo 1997, experiment 1

14. space-based attentional effects
masking with four-dot mask not only
due to low-level contour interactions
Enns and DiLollo 1997, experiment 1

15. space-based attentional effects
masking insensitive to contour
proximity at parafoveal locations
Enns and DiLollo 1997, experiment 2

16. space-based attentional effects
four-dot masking increased with number of targets
Enns and DiLollo 1997, experiment 3

17. space-based attentional effects
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
Enns and DiLollo 1997

18. space-based attentional effects
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. »
Enns and DiLollo 1997

19. space-based attentional effects
masking increased with number of targets
Tata 2002, experiment 1

20. space-based attentional effects
correct attentional cue decreased masking
Tata 2002, experiment 2

21. space-based attentional effects
pop-out effect reduced masking
Tata 2002, experiment 3

22. space-based attentional effects
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
Tata 2002

23. 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.

24. 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.

25. 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.

26. central attentional effects
mechanisms of masking:
integration through common synthesis
interchannel inhibition
replacement principle
Michaels and Turvey 1979

27. central attentional effects
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
Enns and DiLollo 1997

28. central attentional effects
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
Enns and DiLollo 1997

29. 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
Breitmeyer and ögmen 2006

30. 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
Breitmeyer and ögmen 2006

31. 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
Breitmeyer and ögmen 2006

32. 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 »
Breitmeyer and ögmen 2006

33. thank you for your attention at the lecture