A Comparison of fortunes: the comparator and multifactorial weighting models of the sense of agency

The sense of agency over bodily actions is the feeling that one is the agent of one's actions. In this paper I examine the prospects of Frith and colleagues' influential comparator account of how the sense of agency over one's bodily actions is elicited, in comparison to the multifactorial weighting model advocated by Synofzik and colleagues in response to some problems with this account. I examine two problems for the comparator model. I consider the common objection that the actual sensory consequences of action aren't needed to elicit the sense of agency with a look at the data which most strongly suggests this, namely the preserved sense of agency over phantom limb movements. I consider a problem for the comparator model in the behaviour of normal subjects placed in unusual circumstances, in particular I consider the 'wheel of fortune' studies which some take to be problematic for the comparator model. I argue that neither of these objections are devastating for the comparator model and that the comparator model plus some plausible assumptions can explain these data. However, these assumptions are not part of the original comparator model. In the end we get a version of the comparator model modified to deal with problematic cases in a manner that could be seen as somewhat ad hoc. To deal with this the multifactorial weighting model of Synofzik and colleagues is introduced. Although this model is incomplete a single version can be offered which is naturally constrained by the cases which are problematic for the comparator model. However, it is not clear what, if anything, could count as evidence against the multifactorial weighting model. Despite being generated with the data in mind it may be untestable. I conclude that currently the comparator model has stronger support than the multifactorial weighting model.