So here is a weird thing to say:

I look out of the window and I think that the garden looks nice and the grass looks cool, but the thoughts of Eamon Andrews come into my mind. There are no other thoughts there, only his…He treats my mind like a screen and flashes his thoughts onto it like you flash a picture (Mellor 1970 p. 17).

Now there’s lots to be baffled by here (not the least of which being: who the hell is Eamon Andrews? – he’s an old British TV presenter), and it’s just that sense of bafflement that I want to highlight. What is this person claiming? That someone else is thinking in their mind? What on Earth would that be like? This isn’t trivial. No one else ever thinks using my mind and only you ever think with yours. How can we even understand what this person is saying?

Well, when I tell you that this statement comes from a person suffering from schizophrenia you might be tempted to dismiss the statement as a semi-random sequence of words, which certainly sounds like an English sentence, but not one which in anyway reflects the experiences the subject is actually having. Maybe this isn’t a report of an experience the patient has, but rather what we hear from them is an empty sequence of words- perhaps the result of thought derailment- more closely related to what is insensitively referred to as “incomprehensible ramblings” than the kind of delusion we saw last time out.

There are a number of considerations which speak against this. The first is the sheer consistency of patient’s reports. Patients don’t just say this once; it is something they claim over extended periods of time. The second is the number of patients making claims around this theme; it just isn’t likely that so many people would randomly produce such sentences. The third is that patients make this kind of claim even when they don’t show other signs of symptoms such as thought derailment. Overall, then, it seems the burden is on us to try and understand what these patients are saying about their experiences, rather than dismiss them as incomprehensible.

Well how might we start to do so? Last time out with delusions of alien control the problem didn’t arise; I just highlighted a common experience and suggested that the delusion arose from a bizarre form of that experience. But what kind of experience, familiar experience, could be altered to give rise to this kind of belief, these “delusions of thought insertion”.

One popular approach has actually been to relate these delusions to delusions of alien control. As delusions of alien control involve a deficit in the sense of agency over bodily actions, perhaps delusions of thought insertion involve a deficit in the sense of agency over mental actions. Just as delusions of alien control arise because the patient doesn’t feel like they control their own actions, perhaps delusions of thought insertion arise because the patient doesn’t feel like they control their thoughts?

However an explanation such as this may work it cannot be the same as what we saw last time out for alien control. Recall the mechanism which we thought was important for this delusion involved a representation of actual sensory feedback, however, in the case of thoughts there isn’t actual sensory feedback to be had. So we’re looking for a different, but perhaps in some way analogous mechanism.

All well and good, but there is a bigger problem for trying to extend this kind of account for delusions of alien control to explain thought insertion. I left a part of the explanation last time out hidden. In order to come up with something as weird as feeling that someone else is controlling your actions it is supposed that lacking a feeling of agency is somehow anomalous. The patient is thought to come up with the delusion to explain their experience because the experience is weird. It’s unexpected. This stage is needed to get us from “feeling that I didn’t do it” to “feeling person x did it”.

Is this move plausible for accounts of delusions of thought insertion? Well there are a few worries to be had. First, if you’re anything like me, you might not find it so weird to
think that such and such a thought you have wasn’t under your control, maybe it just popped into your head, out of the blue as it were. If that sort of consideration is right then just how noticeable would thoughts for which the patient lacks a sense of agency be noticeable? Maybe thinking thoughts one doesn’t seem to control isn’t as anomalous as performing actions one doesn’t seem to control. Second, we might worry about the nature of the delusional belief the patient ends up with. It certainly makes sense to attribute your actions to someone else- this really happens, as in the simultaneous door opening effect we saw last time. But it is in fact the case that no one else can put their thoughts in your mind (i.e. put them in directly, without an act of communication- the patient quotes above certainly doesn’t seem to be saying that Eamon Andrews is communicating his thoughts to her, it’s something more direct than that.)

Well I must admit that the second of these problems still baffles me, but I think some progress has been made on the first. The more radical proposal I have made around this is to suppose that patients suffering from these delusions don’t lack a sense of agency when they ought to have it; rather they lack a sense of agency over their thoughts and this accurately reflects the fact that they have lost, a rather specific kind of, control over some of their thoughts. In particular it seems that what they lose, sometimes for some thoughts, is the capacity to try not to have the thought.

Trying not to have a thought, or trying not to think about something, is in one way very hard to do… “God I want the Thomas the Tank Engine theme song out of my head”, so I don’t want to be read as saying that normally we are good at directing our thoughts away from certain topics. Rather what is important to note is that usually what we can do is pick out thoughts we don’t want to have and then trying to supress it. This is the capacity which seems to be failing in delusions of thought insertion.

The evidence for this comes from studies where experimenters try and create particular thoughts in their subjects and then direct them not to act on the thought. We might do this be giving subjects a list of sentence stems, like “The dough was put in the hot ____” and then directing subject’s to finish the sentence in a way that doesn’t make sense. Here the experimenter tries to make the subject think the word “oven” but then the subject is required to inhibit this word, and come up with another. It turns out that patients suffering from delusions of thought insertion (and some related symptoms, just to make it complex!) are worse at these sorts of tasks than people who don’t suffer from these symptoms (Waters et al. 2003).

I still don’t know why patient’s go from this to attributing the thought to someone else, but I think progress is being made here.

You can read my full account of this in my paper:

“A metacognitive model of the sense of agency over thoughts.” Cognitive Neuropsychiatry 17(4): 291-314.

And that’s something else that I do.

With love

DrNPC

References

Mellor, C. S. (1970). “First Rank Symptoms of Schizophrenia.” The British Journal of Psychiatry 117(536): 15-23.

Waters, F. A. V., J. C. Badcock, M. T. Maybery and P. T. Michie (2003). “Inhibition in schizophrenia: Association with auditory hallucinations.” Schizophrenia Research 62(3): 275-280.