Gender Differences In Planning?

We all know that there are gender differences in neuroanatomy, as well as in some cognitive tasks (females tend to do better on memory and verbal tasks, men on spatial tasks) and both cognitive and emotional development, though it's not clear how the cognitive/behavioral/developmental differences relate to the differences in neuroanatomy. Research on gender differences is often plagued by confounding variables such as sociological factors that are damn near impossible to control for. Jumping into the gender-differences game takes a lot of guts, or extreme naivete, then, because not only is your research going to be subject to increased scrutiny that comes with politically-charged rsearch, but it's inevitably going to be inadequate as well. That's certainly true of the latest entry into the gender differences literature, a paper by Boghi and 600 other people (neuroscientists travel in packs) in the November issue of NeuroImage on gender differences in planning in particular1. Before I get to the criticisms, though, I should probably describe the paper.

The study described in the paper uses the Tower of London task. In this task, there are three poles and a number of discs on the poles (usually 5 discs total). The goal of the game is to take the discs and move them so that they are in some pre-assigned arrangement, and to do so in as few moves as possible. The rules are that you can only move one disc at a time, and can only move a disc when there are no discs on top of it. Here's a figure that shows an example of the setup, with the top image representing the goal, and the bottom image representing the starting configuration2:

This task has been used extensively to study planning, so it's not surprising that Boghi at al. would choose it. In planning versions, people are asked to think about how to complete the task before they actually do it. Of course, they had participants strapped into fMRI machines, so it wasn't really possible for the participants to actually move discs (or in their version, balls) on the poles. Instead, they had participants think about the minimum number of moves it would take to reach the goal state from the starting position, and then report this (in a whisper) to the experimenter. While they were figuring it out, pretty pictures were taken of their brains.

Now, both males and females do equally well on the Tower of London task generally, and Boghi et al. found no gender differences in task performance, but they weren't interested in performance differences. They were interested in differences in brain pictures. When they contrasted activation during the performance of the task for males and females, they found greater activation in the female participants than the male participants in the dorsolateral prefrontal cortex (DPC; working memory) and right parietal cortex (attention). The male participants showed greater activation than the female participants in the precuneus, an area associated with spatial reasoning. Boghi et al. interpret these results as indicating that the female participants used more executive strategies for planning (working memory is considered an executive function), while the males relied more on spatial reasoning, an interpretation consistent with the gender differences I mentioned above. Boghi et al. argue that these differences reflect differences in planning strategies.

Buuuuuut there are problems. Putting aside the epistemological problems involved in making inferences about cognitive processes from neuroimaging data, the first problem with the study is that while the Tower of London task has been widely used to study planning, very little research has been conducted to determine exactly what cognitive functions are involved in performing the task. In fact, recent research has raised questions about whether planning is involved in the Tower of London task at all3. Furthermore, we do know that memory does plan an important role in the task4. It would not be unreasonable to interpret Boghi et al.'s results as simply showing that, because women tend to do better on tasks involving memory, when performing the Tower of London task, men more than women have to rely more on on-line spatial reasoning to perform as well. It might be interesting to learn that when mentally performing a task involving verbal, executive processes and visuo-spatial processes, women rely more on the verbal, executive ones, while men use more visuo-spatial ones, but I don't think it is. I mean, we already knew that. So it's not clear, then, that these results say anything about planning and gender, or anything new at all.

¹ * Boghi A., Rasetti R., Avidano F., Manzone C., Orsi L., D'Agata F., Caroppo P., Bergui M., Rocca P., Pulvirenti L., Bradac G.B., Bogetto F., Mutani R., Mortara P. (2006). The effect of gender on planning: An fMRI study using the Tower of London task. NeuroImage, 33(3), 999-1010.
² From Phillips, L.H., Wynn, V.E., McPherson, S. & Gilhooly, K.J. (2001). Mental planning and the Tower of London task. Quarterly Journal of Experimental Psychology, A, 54(2), 579-598.
³Ibid.
⁴Phillips, L.H., Wynn, V., Gilhooly, K. J., Della Sala, S., & Logie, R. H. (1999). The role of memory in the Tower of London task. Memory, 7, 209-231.