Decartes’ (Other) Error

August 22, 2009

There is something called Descartes’ Error; it’s too hard for me to explain.  But Descartes did say that we should doubt everything, and that includes our senses.  Blasphemy!  Our senses are all we have to live by, and if I can’t be sure about them, how can I even be sure of my thinking or doubting since all I think or doubt is that which I perceive?  Well, that was enough armchair philosophy for the day.

You might expect that doubting your senses would induce you to check that pilot light once more (did you really see it was lit, or did you forget), but it turns out that perseverative checking, that is, looking at a word over and over again or looking at the pilot light now and now and now, can create a doubt of your senses, doubt of your memory, and dissociation of the self.

The study took healthy students and asked them to stare at a light or flame for a period of time. There were three staring sessions per student ordered by time (10 sec-10min-10sec) – some with gas-gas-gas, some light-light-light, some gas-light-gas, and finally some light-gas-light in order to see if changing stimuli changed derealization and uncertainty.  After the first and last staring session  the students completed a questionnaire that measured derealization and uncertainty.

It turned out that these healthy students who had no history of mental illness were induced to show symptoms extremely similar to patients with Obsessive-Compulsive Disorder (OCD).  Though not statistically significant, the students who stared at the same thing for all three sessions showed the symptoms more strongly.  I would guess that if the number of subject were increased this would come out to be a significant difference.  What the researchers found in this case was that uncertainty of memory and perception increased more than dissociation, but there was a moderately strong positive correlation between the two (pearson’s r=0.43).

Another interesting thing the authors talk about in the discussion is that OCD behaviors seem to be the person explicitly taking over and implicit process.   Most of the time people read words without conciously trying to read them – hence the stroop task for experiments which try to induce error – but in OCD it seems that individuals try to conciously take over this process.  The authors mention something that it is likely everyone has experienced – reading a word many times and suddenly, the word seems strange and foreign to you, for some reason it is odd that this word goes with the definition it has been given, why is it spelled that way, wait . . . what is the word?  Many of our brain processes actually work better in automatic than in forced overdrive: immediately think of 9 negative memories from your childhood.  Pretty hard.  But if you are promted by a stimulus suddenly a memory will come rushing back to you.

That prompting is called spreading activation in cognitive psychology.  There are memories, items, places, smells, tastes, etc. that are interlinked in our minds (we all know this already, but sometimes we can be oblivious to the obvious), when one of those things becomes reactivated it gives some activation to those ideas that surround it.  This is just an analogy, but think of each individual sense, like the taste of peanut butter as a neuron connected to 5 other neurons: Nelson’s chocolate peanut butter icecream, mom’s PB&J’s, PB in your hair, thai peanut sauce, and toast.  When you take the peanut butter out of the cupboard that one neuron gets activated and sends out a little spark to all those connected to it and all of a sudden you have a bunch of ideas about what to do with the PB, a craving for ice cream, and memories of eating PB&J with mommy in the park.

It turns out that taking that automatic process over with explicit functioning weakens it by raising performance standards and makes one less confident of one’s memory and/or perceptions.  Maybe Descartes was a bit OCD and that’s why he hated his senses.

The authors finish up the paper with the conclusion that the best therapy for OCD and checking behaviors are then Exposure and Ritual Prevention Therapies, which are already conducted with people with OCD.  However, this does shed new light on why they work, and it may allow clinicians to focus their energies on therapies that are more effective, thus making treatment a shorter period (and more appealling for insurance companies to pay for).

van den Hout, M.A., Engelhard, I.M., de Boer, C., du Bois, A., & Dek, E. (2008). Perseverative and compulsive-like staring causes uncertainty about perception. Behavior Research and Therapy, 46, 1300-1304.


One Response to “Decartes’ (Other) Error”

  1. megan said

    so when OCD patients continuously check, let’s say, light switches and they find they indeed turned them off- they must feel a decreased sense of anxiety and nervousness, therefore wouldn’t that be a negative reinforcement? the temporary relief? does this explain why the behavior increases over time and reaches over into other stimuli? they feel rewarded, briefly, and in turn feel rational in their compulsions?

    another thing i was thinking about, descartes also believed in the dualism of rationality and emotion. he believed that we function solely on a pragmatic machine and that our thought processes are entirely void of sensual, emotional or environmental factors. does this have anything to do with OCD?

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