Higher order intentionality tasks are cognitively more demanding

Abstract

A central assumption that underpins much of the discussion of the role played by social cognition in brain evolution is that social cognition is unusually cognitively demanding. This assumption has never been tested. Here, we use a task in which participants read stories and then answered questions about the stories in a behavioural experiment (39 participants) and an fMRI experiment (17 participants) to show that mentalising requires more time for responses than factual memory of a matched complexity and also that higher orders of mentalising are disproportionately more demanding and require the recruitment of more neurons in brain regions known to be associated with theory of mind, including insula, posterior STS, temporal pole and cerebellum. These results have significant implications both for models of brain function and for models of brain evolution.

Keywords: fMRI; intentionality; mentalising; reaction time; social brain.

Fig. 1.

The basic design for Experiments 1 and 2.

Fig. 2.

Experiment 1: Mean reaction times of subjects when correctly answering questions at each level on mentalising (solid symbols) or factual (open symbols) recall (N = 39 subjects). Error bars are ± 1 SEM.

Fig. 3.

Mean (±SE) for reaction time (in ms) as a function of the proportion of questions correctly answered at any given mentalising or factual level, for mentalising (solid symbols) vs factual (unfilled symbols). Data from Experiment 1.

Fig. 4.

Experiment 2: fMRI results showing (A) a broad pattern of response to the contrast intentionality > memory, (B) a more circumscribed response to the parametric modulation of difficulty levels in the intentionality vs factual memory tasks, and (C) the results from A (in yellow) and B (in red) plotted together. All responses shown are significant at P < 0.05 whole-brain corrected, as specified in the methods section.