Do we also think to really see what we see ?

So , I happened to encounter this very question forming the post title — “Do we also think to really see what we see ? And can we see what we think ? Can there be dissonance in what we think we see and what we see through our eyes ?” which prompted me to do this blog post. Vision — How often do you think we think about vision that we possess ? For most of us , it is only another sense which we take for granted . We wake up in the morning , open our eyes and tada , everything is there in front of us. So how do you think our visual system work ? Two eyes with iris , retina , pupils , cornea and some complex nerves detect light and we see exactly what is around ? Yes ? Well , No. It’s a lot more complex. But who cares , right ? To know and perceive a pattern , it takes much more than the eye’s ability to detect a beam of light. Differentiating a sphere from a square is not an eye only task. Number of steps and comparison are involved in knowing whether a light beam falling on the retina has been reflected off a square object or a spherical one. We have good reasons to trust that we generally perceive the world correctly. When we see a building, it is quite likely that a building is really there. Unremarkable yet formidable right ? Identification of an object based on shape and position definitely doesn’t seem achievable only with the help of the pair of eyes we are blessed with , or does it seem like it is just the eyes and the light ? Well , when we see a square, the image of it that falls on our retina is not square-shaped . How, then, do we differentiate it from a rectangle, or a trapezoid?

The answer is not obvious — that is, we don’t simply see the square as a square because that’s the object shape.

Perceiving light ≠Perceiving shapes or objects

The perceptual system of vision does more than construction of an accurate representation. Also , have you ever thought that orientation could affect recognition ? It could and it actually does. Proof of that lie in the study that Shepard and Metzler conducted years ago back in the 70's.

It is not the perception of unfamiliar objects that takes long but it is the identification that consumes time. The perception is almost immediate. Spatial relations and orientation play a major role here.

And here is a fun game for you for which you may use your stop-watch. Observe the time taken to read the top two lines and the bottom two lines.

Text explaining how orientation and spatial relation affect visual perception

Which one do you think can be read faster ? the below one ? the above one ?

You are wrong if you think it is the above one that can be read faster. There is elimination of the spatial relations among letters that are encoded in whole-word representations that slows down the entire reading process.

Ultimately, spatial representations are what all visual representations are comprised of. The first information encoded are the orientations of edges. Be it while reading a sentence, recognising a face, or during navigation , the visual representation encodes the spatial relations among features. Not just that but we need to note that the perceptual representation is also guided by memory .

And yes , there are these ventral and dorsal visual pathways that affect the perceptual experience and actions. While the pathways are anatomically distinct, they are also functionally integrated.

Fig : Visual pathway Source : Cognition — Arnold Lewis Glass , Cambridge University Press

To anatomically , put it all , Visual information is transmitted from the retina by the visual pathway to the superior colliculus and thalamus and from the thalamus to the occipital cortex and parietal cortex.

Also , there are huge line of evidences that say that our perception can remain constant even though the image continue to alter. Every time we swivel our eyeballs while observing everyday scenes , the image on each retina races across our photoreceptors at tremendous speed — much like the blur we see when we pan our video camera across the room we are at. But when we move our eyes around , we don’t see the objects darting all over the place or the world zooming past us at warp speed. The world seems perfectly stable — it doesn’t seem to move around even though the image is moving on our retina. The reason is that our brain’s visual centers have been “tipped off” in advance by motor centers controlling our eye movements. Each time a motor area sends a command to our eyeball muscles , causing them to move , it also sends a command to visual centers saying “ Ignore this motion , doesn’t look real “ . Of course , all of this take place without conscious thought. The computation is built into the visual modules of our brain to prevent us from being distracted by spurious motion signals each time we glance around the room.

Also , speaking of dissonance in visual perception — it occurs where there is damage in the visual pathway i.e in conditions like agnosia.

And not to forget , do you know that even when we close our eyes the neurons associated with our retina and the early stages of our visual pathways continuously keep sending baseline activity ?

So , now out of the wrong assumption that our brain recreates a pixel by pixel rendering of the visual image , are you ?

PS — Read on findings by Gregory , Albright , David Marr , Arnold lewis glass , Snowden , V S Ramachandran , Thompson , Cowey if you can spare some time , that is. They are considered quite close to gods in the subfield that is vision and perception. Spare me if i left mentioning other major contributors.