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Geometric vs Featural Processing: Are They Lateralized in Humans?
Stephanie E Tanninen and David R Brodbeck (@dbrodbeck)
Department of Psychology, Algoma University, Sault Ste. Marie, ON, Canada
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Introduction
• Cheng (1986) got the ball rolling– Or the cocoa puff, as the case may be…
• Basically, he found that rats would use geometric information to locate food in a rectangular arena– Most of their errors were to rotations of the
originally baited location
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Cheng (1986)• He then applied featural
information– walls– corners
• The rats still made errors, though most of these were rotational errors
• He concluded that the rats were responding to the geometry of the box.
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Hermer and Spelke (1994)• Tried the Cheng task with
toddlers and adults• Disoriented the subjects• Using a cue• Toddlers are not unlike rats• Adults are different, seem
to follow the cue• Same in Pike (2001)
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Brodbeck et al (2003)
• We spun a rectangle with a fading red dot• Subjects were asked to say where the dot was
after 8 sec of spinning• Subjects relied on geometry pretty much
completely, until it became useless (when using a square)
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Cued Rectangle Results
Original Dot Location
37.2% +/- 3.58
Reflection Error
11.6% +/- 3.38
Reflection Error
10.8% +/- 2.88
Rotational Error
40.4% +/- 3.62
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Cued Square
Original Dot Location
34.2% +/- 2.79
Reflection Error
23.2% +/- 3.63
Reflection Error
28.0% +/- 3.01
Rotational Error
14.6% +/- 3.77
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Vallortigara et al 2004
• Trained chicks on the task
• Covered one eye, or the other
• Also tested both eyes uncovered
• lateralized
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We wondered
• As we get similar results in humans and other animals
• As Human spatial tasks are generally lateralized
• Are results in the spinning rectangle task lateralized?
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Method
• Subjects had a white rectangle presented to them on a monitor
• Presented binocularly, left field, right field• A red dot was in one of the corners• The dot faded• Where was the dot?• Using either a feature (yellow strip) or not
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What We Expected
• We figured they would follow the feature more in the right visual field condition (left field, right hemisphere = space, that sort of thing)
• So, basically an interaction of viewing condition (left, binocular and right) and feature presence or absence
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Results
• The results did not differ depending on visual field
• We also did not get the error pattern from Brodbeck et al (2003)
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What does this all mean?
• Well, the pattern of errors did not change depending on visual field which leads us to conclude, for the moment, that this task is not lateralized in humans
• Makes some sense, we are not birds, we have a corpus callossum
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Yeah but….
• We also did not find the pattern of errors we expected
• This is likely a matter of the speed of the spinning rectangle
• We used 90 rpm, Brodbeck et al used 480• We found some suggestive sex differences,
(males making more rotational errors) but we only had 5 men vs 17 women
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Future directions
• Try again making the task harder (our goal here was not to replicate so much as to look for a suggestion of lateralization)
• When does a square become a rectangle?• Is that perhaps lateralized, or are there sex
differences?
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Thanks to