Sunday, April 8, 2012

Spatial ability and socio-economic status

One of the most persistent, and pronounced, findings in gender differences with regards to cognitive performance has to do with spatial skills, in general, and Mental Rotation, in particular (see Linn & Petersen, 1985) - a gap that, except for some notable exceptions (Eastern Canadian Eskimos and Icelanders), seems to hold cross-culturally (Mann, Sasanuma, & Sakuma, 1990).

Fig 1 from Levine et al. 2005

In their 2005 paper -Socioeconomic status modifies the sex difference in spatial skill - Levine, Vasilyeva, Lourenco, Newcombe, and Huttenlocher present the results of a longitudinal study that ran over two years with the intention of investigating what, if any, effect Socioeconomic Status (SES) has on this gender gap in spatial ability. In understanding the differences between male and female spatial skills it's essential to get a handle on whether the observed differences are mainly a function of biology or mainly a function of culture, given that generally any interesting trait is going to be affected by both. This is especially important in the present case because it has been shown that spatial skills tend to correlate with performance in mathematics based subjects - areas where females have traditionally been under-represented. Understanding this gender based performance difference may help enable educators better address the disparity of representation in STEM subjects (see, for example, Cherney, 2008).

SES status was assigned at a school level on the basis of census-track data for Illinois. A total of 547 students were recruited for the experiment, with male and female participants being approximately equally represented across all three SES groups. Testing consisted of administering an aerial-map task (participants are asked to draw correspondences between aerial photographs of an area and a map of the same area), a mental rotation task (based on "the Spatial Relations subtest from the Primary Mental Abilities (PMA) Readiness Level" (Levine et al., 2005: 842)), and a syntax comprehension test. 

Given previous findings, Levine et al. expected to see gender differences in the spatial tasks but not the language task - an expectation that was mostly borne out by their results with one exception. Their findings show (fig 1) that the expected differences in spatial skill held only for middle and high income subjects - low SES male and female subjects failed to show any significant differences in their performance on the aerial-map and mental rotation tasks. That is, in Levine et al's study, the gender gap is virtually non-existent for the low income group. 

The researchers posit two possible explanations for their findings. The first starts with the observation that generally the gender difference manifests itself in the more difficult test items - if both male and female low-SES group subjects failed to succeed in answering the more difficult questions then that difference wouldn't be apparent in the data even if a difference did in fact exist. However, further analysis of their data seems not to support this hypothesis, for example, a difference in spatial ability for the low-SES group did not manifest in the subset of data where performance across all three groups was comparable for spatial tasks while the difference persisted for the higher groups. 
The second possible explanation for the results, and the one the researchers (and their data) seem to favour, is the notion that it is "differentially high level[s] of engagement in the kinds of activities that promote the development of spatial skill[s]" (Levine et al., 2005: 884) that causes the gender gap in spatial ability, and that these kinds of activities (playing with particular toys, freely exploring their neighbourhoods, etc.) might not be readily available to males from low-SES groups, or - at least - as readily available to males as they are to females. 


References:

Cherney, I. D. (2008). Mom, Let Me Play More Computer Games: They Improve My Mental Rotation Skills. Sex Roles, 59(11-12), 776-786. 

Levine, S. C., Vasilyeva, M., Lourenco, S. F., Newcombe, N. S., & Huttenlocher, J. (2005). Socioeconomic status modifies the sex difference in spatial skill. Psychological science, 16(11), 841-5. 

Linn, M. C., & Petersen, A. C. (1985). Emergence and Characterization of Sex Differences in Spatial Ability: A Meta-Analysis. Child Development, 56(6), 1479. 

Mann, V., Sasanuma, S., & Sakuma, N. (1990). Sex differences in cognitive abilities: A cross-cultural perspective. Neuropsychologia, 28(10).

Wednesday, April 4, 2012

Mental Rotation in Preschoolers

Kids and spinning - a random
unrelated picture
I recently came across an interesting paper by Ping, Ratliff, Hickey, & Levine called Using Manual Rotation and Gesture to Improve Mental Rotation in Preschoolers that might have some implications for my own research. If you're so inclined you can grab a copy of the paper here.

Ping et al's research takes its orientation from studies that show that Mental Rotation is in some respects linked with motor processes, as well as research that shows that propensity to gesture during an MR task is positively correlated with  MR performance (I'll be covering this research soon).

The aim of the study was, then, to investigate the effectiveness of two different training methods on MR performance. The experiment had a standard pre post control design - 63 four year olds were randomly assigned to one of three conditions (two experimental conditions and a control condition) and were administered pre and post-tests assessing their speed and accuracy during a Mental Rotation task.

 The first training condition presented the children with two images of an animal - one of the images was presented in an upright orientation (i.e. the animal was on its feet) while the other was rotated around its centre at one of four different orientations. The children in this condition were then required to bring the rotated image into the same orientation as the upright image by using a joystick that would actually rotate the image clockwise or anti-clockwise in response to the children moving the joystick left and right.
 The second training condition was almost exactly like the first except instead of using a joystick to bring the rotated image into the same orientation as the target image, the children were asked to reach for the image on the screen, pretend that they were grabbing and then rotating the image to bring it in line with the upright image.
Finally, the control condition spent their time performing a task that didn't involve rotation.

The pre and post tests were a more or less standard 2D version of the Shepard-Metzler style MR test - but using images of animals instead of the usual collection of blocks or polygons that are used in these kinds of tests. As well as the Child Mental Transformation Task (CMTT), which was used to measure transfer.

The results were rather interesting (especially point 3 below) - here's a summary:
  1. Accuracy and speed improved significantly across all three groups - this is standard stuff, MR tends to have a serious practice-effect.
  2. Accuracy improved significantly on the gesture condition compared to the control condition, while the Joystick rotation condition wasn't significantly different from either of the other two conditions.
  3. For MR Reaction Time both the Gesture condition and the control condition showed significant gains on the Joystick rotation condition.
  4. Further analysis of the data revealed that (3) was explained by the pattern of improvement in females, while males tended to speed up similarly across all three conditions.
  5. The same pattern described in 3 and 4 held with transfer to the CMTT 
What's interesting here is that those children that didn't get any training on a task that ostensibly required Mental Rotation improved more than those that were required to physically rotate images.
Ping et al. suggest that what might be happening is that the children physically rotating the object might actually become dependent on this physical rotation while their "pure" MR performance suffers.

Their explanation makes a lot of sense - but I also think that it points to a potential problem in the MR literature. That is, while a lot of thought is given to the design of the experiments, especially the nature of the pre and post-tests, comparatively little thought is given to the nature of the training task. Superficial similarities between Mental Rotation and physically rotating pictures of animals with a joystick are all that seem to be required to justify using the latter as a training task for the former. The fact of the matter is that the computational (broadly construed) task is almost completely different in the two cases. In the one case there is an actual requirement for the subject to mentally rotate an image, in the other there is no mental rotation required at all. Where the two tasks are similar is actually at the point where the two images are compared to see if they are identical. This fact explains why we see improvement in accuracy in the Joystick condition but not in MR Reaction Time performance. The requirements in the Gesture conditions are much closer to the pre and post-tests in this case.