Science · Perception · 1974 onward
Seeing Without Seeing
A man says he is blind in part of the field, and still posts letters through a slot he claims not to see.
- Britain, then many labs
- Late twentieth century
- 51.75°N 1.26°W
Plate · Generated interpretation
What can you name here without a caption, and what remains unavailable?
Listen · Eve
0:00 / —:—
Patient D.B. has a portion of visual cortex removed to treat a growth. In the corresponding part of the visual field he reports darkness. Lawrence Weiskrantz and colleagues ask him, all the same, to guess: is the line horizontal or vertical? Where is the spot? His guesses are far above chance. He thinks the experimenters are asking him to be silly. He is seeing, in a sense the first-person report will not own.
Blindsight (the term is Weiskrantz’s) is a documented dissociation between visual performance and visual awareness after V1 damage, replicated in other patients (including G.Y.) and in animal work. It is not a parlor trick and not a refutation of consciousness. It is a crack in the identity of seeing and knowing that one sees.
The finding forces a distinction the ordinary day conceals. There is vision as a channel that can guide action. There is vision as a presence for a subject. In blindsight they come apart. Philosophers seized on this as evidence that consciousness is something extra: or, conversely, as evidence that our reports of consciousness are crude. The data do not choose the philosophy.
Some accounts invoke residual pathways (collicular, extrastriate) that support action without phenomenal sight. Others argue that “unaware” is too coarse: perhaps a degraded, unreported experience is there. The patient says there is nothing. That testimony is evidence. It is not infallible.
Why it matters
The story unhooks performance from presence. A mind can be in contact with the world and still say, honestly, that the world is not there for it. Any theory of consciousness that cannot make room for that unhooking is too simple.
A word
blindsight
A coinage meant to sting: sight that does not count, for the person, as seeing. The paradox is in the ordinary word.
Distant echoes
Echo
Classical Greece · Athens
The fire and the wall
Prisoners see shadows and take them for things. D.B. sees, in a fashion, and takes it for nothing. Two failures of report, in opposite directions.
Another language
offers another language
Attention in the noisy room
You can hear your name across a party and only then realize you had not been hearing. Presence has a threshold. Blindsight suggests the threshold is not the whole of the channel.
Counterpoint
Analytic philosophy · A gray room that does not exist
Mary’s first red
Mary’s problem is a presence that knowledge had not given. Blindsight is a knowledge-in-action that presence has not given. Two missing pieces, not the same piece.
One question remains
Perception · What does sensing give us?
If some seeing does not belong to someone, is consciousness the name of the belonging, and not of the seeing?