Spatial cognition Lavanya Sharan April 11th, 2011
Jan 07, 2016
Spatial cognitionLavanya SharanApril 11th, 2011
Measuring distance: Under constrained?
Berkeley observed that distance information is lost during retinal projection, thus visual cues are not sufficient
(Proffit 2006).
Measuring distance: Not so constrained
Gibson and Sedgwick noted that visual cues can provide relative depth information (Proffit 2006)
Many cues for distance perception
Occlusions provide ordinal distance information.
(Images: Cutting & Vishton 1995, etsy.com)
Many cues for distance perception
Relative size can provide ordinal and scaling distance information. However, variability in sizes (~10%) makes
this cue non-informative.
(Images: Cutting & Vishton 1995, nysun.com)
Many cues for distance perception
Knowing one’s own height can be useful for absolute or relative distances assuming no floating objects and opaque planar surfaces
that are orthogonal to gravity.
(Images: Cutting & Vishton 1995, newswritingworld.blogspot.com)
Many cues for distance perception
Atmospheric effects can provide depth information (e.g., further objects look bluer and
are decreased in contrast.)
(Images: Cutting & Vishton 1995, city-data.com)
Many cues for distance perception
Observers’ movements through a rigid, mostly planar environment can provide depth information.
(Images: Cutting & Vishton 1995, Proffit 2006)
Many cues for distance perception
To focus at different distances, our eyes accommodate by changing the focal length of our
lenses.
(Images: Cutting & Vishton 1995, eyepower.nl)
Many cues for distance perception
The input to two eyes provides stereo and therefore, depth information.
(Images: Cutting & Vishton 1995, okaygeek.com)
Many cues for distance perception
Motion perspective
Texture gradient
Binocular disparity
Accommodation
Height in visual field
Occlusion Relative sizeAerial
perspective
Why so many? How do they interact?
Cutting & Vishton (1995)
Redundancy is useful. Different cues are effective in different
ranges.
Measuring distance perception
Verbal reports
Visually directed actions
Images: dwellingintheword.wordpress.com, VPfaCGP Fig 13.2, Loomis & Philbeck 2008
Why blind walking?
Image source: napraten.nu
De-emphasize visual cues.
Test whether observers can dynamically update their positions.
Observers are reasonably good at this task.
Klatzky et al. (1990)
However, return-to-origin tasks are hard.
Distance perception: “veridical” or not?
Veridicality means:
• Linear relationship between perceived & physical distance.• Perceptual equality of equal physical intervals.
Distance perception: “veridical” or not?
(Loomis & Philbeck, 2008)
Verbal reports Blind walking
Distance perception: “veridical” or not?
Veridicality:
• Linear relationship between perceived & physical distance.
Perceptual equality of equal physical intervals.(Wagner 1985, Toye 1986, Philbeck et al. 2004)
Depth foreshortening (Images: tileandstonedallas.com, 123rf.com)
Context influences distance perception
Image sources: familychiropracticcenter.wordpress.com, sportclipart.com, meagan-ryanne.blogspot.com
Being tired makes distances seem further.(Proffit et al. 2003, Witt et al. 2004)
Purpose of the task at hand matters. (Witt et al. 2004)
Fear makes distances seem larger.(Schnall et al. 2005, Proffit 2006, Stefanucci 2006)
Beyond distance perception: mental imagery
Roger Shepard (from intropsych.com)
Linear increase in response time with increasing rotation
Parsons (1994)
Body schema and mental imagery
Response time correlated with time to taken to attain pose
Zacks et al. (1992)
The task matters for mental imagery.
Same/different figure vs. left/right hand extendedLinear increase vs. flat response time
Is this evidence for object-based vs. viewer-based transformations?
Implications for computer graphics
Head mounted displays
Virtual worlds (Sistine Chapel in Second Life)
Images: digitalcortex.net, eternallycool.net, cbs19.tv
Desktop displays
Class discussion!