Beecham et al recently conducted an experiment giving a set of subjects two tasks: 1) The SNARC task, which tests whether individuals associate higher numbers with the right hand and lower numbers with the left hand, representing numbers as if along a line, and 2) The SMARC task, which tests a similar effect with lower pitches (i.e., wave frequencies) corresponding to the lower button and higher pitches corresponding to the higher button. Both of these tasks depend on reaction times to test their predictions. About 64% of subjects represented objects in this spatial way on the cognitive tasks, confirming this interesting effect. The other subjects either may not represent objects in the same way, or they may have done it in a spatial manner that is not easily mapped onto the binary reaction time-dependent task. Their other interesting finding is that, although the SNARC and SMARC tasks were highly analogous, there was very little individual overlap in performance between the two tasks, suggesting that the spatial representations of knowledge in different domains are functionally distinct.
Beecham R, Reeve RA, Wilson SJ (2009) Spatial Representations Are Specific to Different Domains of Knowledge. PLoS ONE 4(5): e5543. doi:10.1371/journal.pone.0005543.