Question about blindsight

Blindsight is a neurological condition where a patient claims that they are blind, but when forced to guess about, say, the orientation of a line, they perform above chance. This is usually taken as evidence for nonconscious perception. Furthermore, such results are often interpreted by skeptics as meaning that consciousness is a by-stander and does no real causal work since perception can happen just fine in its absence. In response to these skeptics, philosophers point out that the blindsight is often impoverished compared to normal vision because it is never spontaneous and the “skill” of the nonconscious system has to be demonstrated by forcing the patient to guess. So here’s my question: has a blindsight patient ever been observed in their own home or a familiar environment? And if so, would their ability to navigate around the furniture be hampered if they were blindfolded? If blindfolding them hampered their ability to navigate a familiar environment, this would mean that their nonconscious system is operative in “non-forced” situations. What I want to know then is how blindsight works in ecologically valid situations, and not just in forced guessing scenarios. It seems to me that blindsighters would be better at navigating if they were not blindfolded. After all, if their nonconscious visual system can determine line orientations or the presence of a stimulus, would it not also be able to warn the patient if they were about to walk into a table? If anyone has answers to these questions, or knows where I should look to answer them, that would be most helpful.



Filed under Consciousness, Psychology

5 responses to “Question about blindsight

  1. I think I remember reading about an experiment where they set up a room full of obstacles, and got blindsight patients to try and walk across it (by and large they succeeded). Not quite “ecologically valid”, but perhaps getting there. I’ll try and find you a proper reference for that, unless you’ve already come across the same experiment

    (First time commenter, by the way. I’ve been reading for a few months now, and I’m really enjoying your blog. Came across it when doing research for setting up my own!)

    • Gary Williams

      Hi Joe,

      That’s very helpful! And very interesting. Navigating obstacles is the type of experiment I am thinking about and much more ecologically valid that positing cards into slots.

  2. Here we go:

    They give the reference as: de Gelder, B. et al. Curr. Biol. 18, 24 (2008)

    Hope that helps!

  3. Charles Wolverton

    I’m posting this here instead of with my (looong) comment on the previous post since it may be of interest to others.

    You might find this paper on blindsight interesting:

    It gets into more technical fdetail about visual processing than I can fully digest, but it does address some experiments that may be along the lines you’re asking about.

  4. JB

    Have you found out about the effect of blindfolding people with blindsight yet? I can’t seem to find anything helpful on the question anywhere. Thanks.

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