Tuesday, 30 June 2015

Sense of Agency and Delusions of Alien Control

This is the fifth and final post in a series of posts on the papers published in an issue of Avant on Delusions. Here Glenn Carruthers (pictured above) summarises his paper 'Difficulties for Extending Wegner and Colleagues' Model of the Sense of Agency to Deficits in Delusions of Alien Control'.

One of Christopher Frith's (e.g. 1992) ideas that has really taken hold is that part of the problem in delusions of alien control is a deficit in the sense of agency. Given that the sense of agency is the feeling that one controls one's actions we can see how a deficit in this feeling could lead to people saying things like:

When I reach my hand for the comb it is my hand and arm which move, and my fingers pick up the pen, but I don’t control them… I sit there watching them move, and they are quite independent, what they do is nothing to do with me… I am just a puppet who is manipulated by cosmic strings. When the strings are pulled my body moves and I cannot prevent it. (Mellor 1970: 18)

Perhaps part of the reason such patients think someone is controlling them is that they do not have this normal sense of agency. To investigate this further we would like to know how the sense of agency is elicited and why it is deficient in these cases. There have been a bunch of hypotheses developed to explain this. Here I will focus on one which was developed by Daniel Wegner and his collaborators (Wegner et al 2004; Wegner and Wheatley 1999).

Wegner and colleagues' hypothesised that the sense of agency is elicited when a subject (unconsciously) infers that one or other of their mental states (e.g. an intention) caused their action. This is called the inference to apparent mental state causation and it occurs automatically when three principles are met:

Priority: The mental state occurs at an appropriate time prior to the action.

Consistency: The mental state is consistent with the action (e.g. the intention specifies the action that actually occurred).

Exclusivity: The mental state is the only plausible cause of the action.

Do we have any reason to suppose that any or all of these principles are systematically violated in cases of delusions of alien control? We can think of many ways in which such principles may be violated. The one I want to squeeze in here is the idea that patients suffering from this delusion represent their actions as occurring later than they should, thus violating the principle of priority. For the patient there is too long a gap between their mental states which might cause their actions and the action itself for the mental state to be a plausible cause.

Suggestive evidence for this comes from ‘intentional binding’ studies. This effect is the apparent binding together in time of actions and their effects. After learning that pushing a button produces a tone subjects are asked to estimate when they pushed the button or when the sound occurred. For those actions which are felt to be voluntary subjects estimate that the button press and tone occur closer together in time than when the button press is involuntary (Haggard et al 2002). In healthy subjects this binding is the result of both the action seeming to occur later and the tone seeming to occur earlier in the voluntary button push condition. Importantly for the above hypothesis the lateness of the button push is exaggerated in patients diagnosed with paranoid schizophrenia (Voss et al., 2010). These patients experience their actions as occurring later healthy controls.

Is violation of the principle of priority likely to explain sense of agency deficits associated with delusions of control? It is difficult to see how this deficit would explain action monitoring problems associated with delusions of control. Frith and Done (1989) had patients play a video game in which they fired a gun at a target which appeared on the left or right of a screen by moving a joystick left or right. Errors were induced by altering the relationship between joystick movements and the direction the gun fired. On some trails a rightward movement fired the gun right, on others a rightward movement fired the gun left (and vice versa). Although no worse than healthy controls or those diagnosed with schizophrenia but not suffering from delusions of control at keeping track of this relationship (Frith and Done 1989: 362), those suffering delusions of control failed to correct errors when they couldn’t see the direction the bullet moved after being fired.

The apparent delay in action which violates the principle of priority seems unlikely to be helpful here. Whilst intuitively we may expect a delay in error correction in those suffering delusions of control we would expect this to be of a similar size to the delay suggested by Martin Voss and colleagues study. In this study those suffering from schizophrenia experienced their actions as occurring in the order of 10s of milliseconds later than controls (Voss et al 2010: 3107). In contrast in Frith and Done’s (1989) study the time subjects had to correct their actions before the bullet became visible was two orders of magnitude greater at 2s. Intuitively, it seems those suffering delusions of control would be able to correct within this time if their only problem were the misrepresentation of the time of their action.

It seems that Wegner and colleagues' hypothesis regarding how the sense of agency is elicited could be used to develop an explanation as to how the sense of agency fails to be elicited in delusions of alien control. Yet when it comes to extending this to account for other problems related to this symptom it falls short. That's a shame, but there are options out there which do not face this problem.

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