On Inattentional Agnosia
In a recently published study, Cohen et al showed that, under very naturalistic conditions (viewing 3D natural scene videos in VR), observers often fail to notice that the entire periphery of the visual stimulus has been rendered colorless, i.e. completely desaturated. Cohen et al conclude that the visual periphery is far less colorful than one might have thought. They state this conclusion in several ways:
“these results demonstrate a surprising lack of awareness of peripheral color in everyday life”
-here qualifying the phenomenon as ‘lack of awareness of peripheral color’. Later, they say it less ambiguously: “If color perception in the real world is indeed as sparse as our findings suggest, the final question to consider is how this can be. Why does it intuitively feel like we see so much color when our data suggest we see so little?”.
So, Cohen et al believe that their data suggest we see very little color. This particular claim is logically absurd, however. I explain why in the following:
Cohen et al clearly believe that the phenomenon they present is a case of inattentional blindness. Inattentional blindness phenomena are frequently encountered in visual experience, and are not difficult to bring about in experimental scenarios. Typically, an observer is shown some stimuli connected to an explicit or implicit task; during the course of the task, some unexpected stimulus is inserted, and the observer may fail to notice. These failures to notice are often very retrospectively surprising, since once the observer knows what to look for (once they’ve been debriefed) it is easy to see the missed stimulus. Experimenters often conclude from these results – both the failures to notice and the retrospective surprise - that, in one way or another, the observers (and the rest of us) must see far less than they think they do. But this is not the kind of conclusion that Cohen et al are drawing.
The most famous example of an inattentional blindness phenomenon has got to be Simons and Chabris’ gorilla. In their experiment, observers watched a video of several people playing a ball-passing game. The players move around constantly, throwing the ball back and forth; the observer’s task is to count the number of times that certain players catch the ball. With no warning, halfway through the video, a person in a gorilla suit wanders into the middle of the ballgame, stops and waves at the camera, and then wanders back out of the frame – the ball game continues. Many observers do not notice the gorilla at all!
Simons and Chabris used this and similar results to advance a version of the “we see less than we think” argument. But what if we transplant Cohen et al’s conclusion to the gorilla experiment?
Here is a sentence in general terms that describes both studies:
“Observers viewed a complex stimulus that engaged their visual attention. After a while, a change was introduced to the stimulus that was retrospectively obvious. Many observers did not notice the change.”
Now, here is the reasonable, broad conclusion (a la Simons & Chabris):
“We must not notice as many things as we would expect based on what seems to be obviously noticeable.”
And here is the unreasonable, specific conclusion (a la Cohen et al):
“We must always be having the kinds of experiences evoked by the changed stimulus.”
In the Cohen et al study, they replaced a colorful scene with a colorless scene; observers didn’t notice; so, according to their reasoning, we must actually be having colorless experiences all the time (or more precisely, experiences of “so little” color). Otherwise, the reasoning seems to go, we would notice the change from colorful to colorless. We don’t notice it because it was colorless all along (they do include a caveat that maybe it’s the other way around, that even the grayscale scene evokes a colorful ‘filled-in’ experience, but that doesn’t seem to be their favored interpretation).
For the gorilla study, a gorilla was introduced incongruously into a ball game; observers didn’t notice; so, we must actually be having experiences of incongruous gorillas all the time (or, maybe more precisely, experiences of gorillas in ball games?). Otherwise, we would notice the change from a no-gorilla to an incongruous-gorilla scene. I don’t want to go on with this because it’s obviously absurd. But isn’t it the same logic as the color argument?
The absurdity comes in part from arguing from a complete lack of evidence: they are taking absence of evidence (failure to notice the change) to be evidence of absence (of color experiences). The experiments they are doing have no bearing, it seems to me, on whether or not their observers are actually experiencing color in their peripheral vision.
But more than this, the absurd conclusion comes from a lack of engagement with the important concepts at play. Color, most importantly. What does it mean to see color? That's for another time, I guess.
Before I finish here, an attempt at charity:
Perhaps the logic Cohen et al would derive from Simons & Chabris is somewhere in between the broad & reasonable, and the narrow and unreasonable:
"If we do not notice something, we are not experiencing it."
This is a strong claim, which I know that Cohen et al and many others would more-or-less endorse. But it does demand some engagement with some basic questions: if one's experience is colorless, what is it like? Is it like experience of a monochrome scene? Why are shades of gray excluded from 'color' status? What is special about 'chromatic hues'? Is there really less to seeing a monochrome scene than there is to seeing a color scene? Think about it: if you are seeing a spot as blue, that precludes your seeing it as any shade of gray, just as much as it precludes it from being yellow or red or whatever. Each part of the visual field always - it seems, at least - has some color in the broad sense.
In fact, Cohen et al did find that subjects always noticed if all color, in the broad sense, was removed from the periphery, i.e. if it were replaced with a flat gray field. Which would seem to defeat their basic conclusion that we are not seeing color, or much color. So, again, what is supposed to be so special about chromatic hues? Interesting questions, definitely.
