Suddenly Susan

30 mars 2010 | In Books Meta-philosophy Psychology Self-indulgence | 2 Comments


First of all: I like Susan Blackmore. In fact, I met her once, at the first proper conference I ever attended (the ”Toward a Science of Consciousness” conference in Tuscon 2004 hosted by David ”madman at the helm” Chalmers). She came and sat next to me during the introductory speech and asked me what had just been said. I said I hadn’t payed that much attention, to be honest, but I seemed to remember a name being uttered. We then proceeded to reconstruct the message and ended up having a short, exciting discussion about sensory memory traces. From now on, I remember thinking (having to dig deeper than just in the sensory memory traces, which will all have evaporated by now), this is what life will be like from now on. It hasn’t, quite.

ANYWAY: So I like Susan Blackmore, but today, I’m using her to set an example.

I recently had occasion to read her very short introduction to consciousness in which she take us through the main issues and peccadilloes in and of consciousness research. One of the sections deals with change blindness and she describes one of the funniest experiments ever devised: The experimenter approach a pedestrian (this is at Cornell, for all of you looking to make a cheap point at a talk) and asks for directions. Then two assistants, dressing the part, walks between the experimenter and the pedestrian carrying a door. The experimenter grabs the back end of the door and wanders off, leaving the pedestrian facing one of the assistants instead. And here’s the thing: only 50% of the subjects notice the switch. The other 50% keeps on giving direction to the freshly arrived person, as if nothing has happened.

This is a wonderful illustration of change blindness, and it’s a great conversation piece. You can go ahead and use it to illustrate almost any point you like, but here comes the problem: there is a tendency to overstate the case, especially among philosophers (I’m very much prone to this sort of misuse myself), due to the fact that we usually don’t know, or don’t care much, about statistics. Blackmore ends the section in the following manner:

When people are asked whether they think they would detect such a change they are convinced that they would – but they are wrong.

We have a surprising effect: people don’t notice a change that should be apparent, and as a result you can catch people having faulty assumptions about their own abilities, and no greater fun is to be had anywhere in life. But Blackmore makes a mistake here: People would not be wrong. Only 50% of them would. It’s not even a case of ”odds are, they are wrong”.

I would use this as an example of some other cognitive bias – something to do with our tendency to remember only the exciting bit of a story and then run with it, perhaps – only I’m afraid of committing the same mistake myself.

(Btw: I also considered naming this post ”so Sue me”)


  1. About the statistics here — a lot of basic to intermediate background material on interpreting the results is available; I have read Gilovich (holding a position at Cornell for all you joking people) and some others with pleasure.

    Plus, XKCD, of course:

    Comment by Måns — 11 juli 2010 #

  2. Bonjour,L’illusion est double pour Susan Blackmore: a. l’ide9e qu’il eiasterixt ce que William James a baptise9 le ”flux de la conscience” (angl.: ) d’un cf4te9 et b. la repre9sentation naefve qu’il y aurait une sorte d’homoncule e0 l’inte9rieur de notre crane qui serait en face d’une sorte de home cine9ma…Nous nous vivons comme e9tant un ”homoncule en face d’une sorte de home cine9ma” (ou pour le dire plus techniquement l’ide9e d’une ”the9e2tre carte9sien”) et comme ayant un flux de conscience, mais ces deux e9le9ments sont re9fute9s par la recherche scientifique, et sont donc des illusions.Elle s’oppose bien entendu au dualisme, que l’on retrouve beaucoup en parapsychologie, of9 ils iront jusqu’e0 de9fendre que la conscience ne se situe pas dans le cerveau (le cerveau n’e9tant alors qu’une sorte de re9cepteur: ).Sceptiquement vf4tre,

    Comment by Savan — 17 september 2015 #

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