Ambiguous Images

Mostly when we look at the world, or a picture of part of it, we see just one version of what is there. Though not always. There are pictures which are ambiguous, that is they can be seen in two ways. For example this picture can be seen as either a rabbit or a duck. Our perception of this is usually described as bistable. That is we can see a stable version of either a duck or a rabbit, not both at the same time.


I believe our conscious experience of vision is based on the firing of top-down visual icons, as proposed by RL Gregory . In other words when we think about a duck, our brain searches signals coming from our eyes for a pattern that matches a duck shape stored in memory. This means that miss-perceptions, occasionally including bistable illusions, can also happen to us in everyday life.

Our sensory views of the world are far from complete. They often exclude large objects, even when we are looking for them. I have often heard people say things like “I was looking for that for ages, and there it was in front of me all the time.”

This ability to suddenly see something that was previously missed has an evolutionary value if the thing missed is a potential threat, food or mate. So the perception of one of these will likely be popped in with a surprise. ‘Gosh, that branch is actually a snake!’

Something which is none of these things can be added to our sensory picture with no alerting of conscious self. This is perhaps one of the reasons we experience change blindness. If it does not matter that the person behind the counter is now male instead of female then why should our preconscious brain worry the conscious self about that.

This Ted talk by Dan Dennett includes a section towards the end showing how we can miss quite major changes in our field of vision for quite a while. As you watch that section take note of how he uses verbal prompts to get the audience to notice the changes.

For me this shows how our conscious experience has both a sensory and narrative part, and the narrative can literally tell the sensory what to see.

This image can be seen as either a young or an old woman. If we are thinking of the young woman, in other words our narrative focus is on the young woman, then we see the young woman.


My asking you to now see an old woman and you seeing her is, I believe, evidence of our brain using different systems to process narrative and sensory data. So the change in your narrative about the picture changes what you see. The same holds for directing a viewer’s attention to a change that has been missed in a change blindness experiment.

Earlier in the Ted Talk there is an example of a sudden change in perception being popped into consciousness. When Dan Dennett describes his moment of shock in an art gallery it was because his narrative state was of approaching a Canaletto, not just any painting. For the painting to suddenly change to one by a different artist required a sudden change in his narrative, and this is why he yelled.

Our conscious experience includes both sensory and narrative elements to get our conscious self to act. If no change in action is needed our preconscious brain will change the detail without alerting the conscious self. But if the change means there is a snake, or we are walking to the wrong painting, then the self needs to know. A conscious decision to change direction is prompted.


Reference
Gregory, R. L. (Richard Langton). Eye And Brain; the Psychology of Seeing. New York,McGraw-Hill, 1973.
Image Source:
Jastrow, J. The mind's eye. Popular Science Monthly (1899).
William Ely Hill (1887–1962) - „Puck“, 6. Nov 1915, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3836554