How do we perceive? A guest post by Sal Schiano

In class we learned that sensation is defined as the signals received by our organs through the five senses (sight, hearing, smell, taste & touch).  And perception is how we experience those sensations.  

The Gestalt psychologists, in an attempt to explain how we perceive objects, believed that we group things together in order to interpret information more easily, i.e. we use heuristics to understand the world around us. For example, the law of similarity explains that when we see a row of dots we refer to it as a “row of dots,” rather than repeating “dot” as many times as there are dots in the row.

Perception is influenced by our knowledge of regularities in the environment, for example: if you were to look at a picture of a tree, with half of it cropped out, you would probably know that the object in the picture was a tree. How? Because of our knowledge of certain physical regularities that occur in the physical properties of the environment -- you know that trees in nature have whole, round, large trunks, and branches and leaves on both sides. Just because you cannot see the other half of the tree does not mean it doesn’t exist.

The information the stimulus is giving us (bottom-up processing) is that there is half of a tree. Then your top-down processing acknowledges what you know about trees:  trees do not grow in such a way to only sprout on one side of it, nor are there any living tree trunks out there that are split down the middle. So you know that the picture must be cropped.

Think of waiting at the bus stop and seeing the bus coming, but its way far, down the road. It looks small, you could even cover it up with your thumb if you close one eye, but you know it’s not the small size it appears from a distance because you know there are people on there and that there is still plenty of room left to hold you. You realize that things do not change size just because it appears so. It may appear small from a distance, but that does not mean it is actually small; this is size consistency. All of these concepts occur without us actively thinking about them.