Geometric vs Featural Processing: Are They Lateralized in Humans? Stephanie E Tanninen and David R Brodbeck 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% +/ % +/ Reflection Error 11.6% +/ % +/ Reflection Error 10.8% +/ % +/ Rotational Error 40.4% +/ % +/- 3.62

Cued Square Original Dot Location 34.2% +/ % +/ Reflection Error 23.2% +/ % +/ Reflection Error 28.0% +/ % +/ 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