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

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

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.

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)

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)

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

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

Vallortigara et al 2004

• Trained chicks on the task

• Covered one eye, or the other

• Also tested both eyes uncovered

• lateralized

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?

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

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

Results

• The results did not differ depending on visual field

• We also did not get the error pattern from Brodbeck et al (2003)

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

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

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?

Thanks to