FR9

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FR9
Visual sensing without seeing
Jennifer E. Corbett Ronald A. Rensink
Visual Cognition Lab, Psychology Department,
University of British Columbia, Vancouver, B.C.,
V6K 1Y3
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Introduction

• Once upon a time, scientists thought
• 
  
• Input Seeing
• (conscious visual perception))
  
• Then several studies found
• Seeing
• Input (conscious visual perception)
• Visuomotor Control
• (unconscious visual perception)
• (Bauer, 1984 Merickle Daneman, 1998
  Fernandez-Duque Thornton, 2000 Milner
  Goodale, 1995).
• This study finds Seeing
• Conscious visual perception (visual
  experience)
• Input Sensing
• Unconscious visual perception
  (Non-visual experience)

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How might sensing be separated from seeing?

• Change Blindness is the inability to see changes
  during a visual disruption.
• If change blind observers can correctly sense a
  change, then there
• is evidence of visual sensing without seeing.
• Change blindness has been shown to be reliably
  induced via the
• Flicker Paradigm (Rensink, ORegan Clark,
  1997 Simons Levin, 1997 Rensink, 2000).

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-Alteration continues for 30s, or
until Ss makes both responses. -Ss
respond t1when change is
sensed t2when change is seen. -48
trials, with 6 catch trials. -3 kinds of possible
change


.
Can Change Blind Observers sense the change
before they see it?
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Response times for CAN-SENSE SsOn average,
CAN-SENSE Ss responded to as many catch trials as
ONLY-SEE Ss. Furthermore, even when a false
alarm occurred in CAN-SENSE Ss, it was usually
made far later then a valid sensing response, on
average 9 seconds later, plt10-5,
Is Sensing due to guessing?
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• 2 Trial Types
• Based on Duration, (D t2-t1),
• individual trials were classified
• as a Dlt1sec.(no sensing) b
  Dgt1sec.(sensing)
• Grouping of Ss (n40)
• ONLY-SEE
• blt5
• (n19)
• 2. GUESS
• bgt5
• False alarm rategt50
• (n9)
• 3. CAN-SENSE
• b?5,
• False alarm ratelt50
• (n12)

Sensing is a not an artifact of guessing.
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Is Sensing due to transients?
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The gray field in the Flicker Paradigm was
modified to be gray between As and yellow
between A1s to rule out the possibility of
timing patterns or chrominance transients as the
cause of sensing.

• Response times for CAN-SENSE Ss
• Color flash had little effect on distribution of
• observations among 3 classes, X2(2)0.26pgt.85.
• For CAN-SENSE Ss, color flash also had little
• effect on the incidence of sensing, X2(1) 0.07
• pgt0.7.

Sensing is not an artifact due to transients.
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Is sensing a distinct mode of conscious
perception?

• What if sensing involves the same mechanisms as
  seeing, but with different thresholds?
• If sensing involves a higher threshold, in any
  b?trial, sensing would happen after seeing. This
  was never the case in Experiments 1 and 2.
• If sensing involves a lower threshold than
  seeing, the average onset for
• sensing should never occur later than the
  average onset of seeing.
• (Figure 2 Average t1(b) is significantly
  greater than t1(a) for both
• presence, plt0.005, and location, plt0.0001.

Sensing and seeing involve different mechanisms.
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Conclusions

• -Approximately 30 of change blind Ss show
  evidence of sensing.
• -CAN-SENSE Ss responded to roughly the same
  amount of catch
• trials as ONLY-SEE Ss, and even when a false
  alarm occurred for
• CAN-SENSE Ss, it was made much later than a
  valid sensing
• response.
• -Color flash had little effect on the incidence
  of sensing.
• -Correct sensing happened in only a small portion
  of b-trials, generally
• occurring before the onset of seeing in any
  trial type.
• -SO, this study provides novel evidence for
  visual sensing as a
• distinct mode of conscious perception not
  caused by guessing,
• transients, or resulting from the same
  mechanisms as seeing.

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References

• Bauer, R. (1984) . Autonomic recognition of names
  and faces in prosopagnosia A neuropsychological
  application of the guilty knowledge test.
  Neuropsychologia, 22, 457-469.
• Fernandez-Duque, D., Thornton, I.M. (2000).
  Change detection without awareness Do explicit
  reports underestimate the representation of
  change in the visual system? Visual Cognition, 7,
  323-344.
• Kihlstrom, J.F. (1996). Perception without
  awareness of what is perceived, learning without
  awareness of what is learned. In M. Velmans
  (Ed.), The science of consciousness
  Psychological, neuropsychological, and clinical
  reviews, (pp. 23-46). London Routledge.
• Merikle, P.M., Daneman, M. (1998).
  Psychological investigations of unconscious
  processing. Journal of Consciousness Studies, 5,
  5-18.
• Milner, A.D., Goodale, M.A. (1995). The
  visual brain in action. Oxford Oxford
  University Press.
• Rensink, R.A. (in press). Visual sensing without
  seeing. Psychological Science.
• Rensink, R.A. (2000). Seeing, sensing, and
  scrutinizing. Vision Research, 40, 1469-1487.
• Rensink, R.A., ORegan, J.K., Clark, J.J.
  (1997). To see or not to see The need for
  attention to perceive changes in scenes.
  Psychological Science, 8, 368-373.
• Simons, D.J., Levin, D.T. (1997). Change
  blindness. Trends in Cognitive Sciences, 1,
  261-267.
• Weiskrantz, L., Warrington, E.K., Sanders, M.D.,
  Marshall, J. (1974). Visual capacity in the
  hemianopic field following a restricted occipital
  ablation. Brain, 97, 709-728.

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Contacts
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FR9 Visual sensing without seeing
Jennifer E. Corbett
Ronald A. Rensink
Visual Cognition Lab, Psychology Department,
University of British Columbia, Vancouver, B.C.,
V6T 1Z4.