Perception

http://joeltalks.com/index.php?p=1_22

Top down processing i.e. the way that individuals project themselves onto their experiences and stimuli to make sense of it. Explains how false memories can be created as a side effect of normal mental processes.

Top-down processing

Top-down processing is a core part of how the brain builds meaning for you to understand. In top-down processing, your mind actively imposes meaning on your perceptions, memories, and understanding of the world. The brain uses top-down processing to create meaning by applying what you already know or expect or believe. This process is what allows you to make sense of the world even if the information you get from the world may be a bit misleading or may be miss some details. 

I talk about top-down processing a lot in my presentations.

Here are a few illustrative examples.  

READING

The literal letter-by-letter reading of the following words would be nonsense. But, you can probably read these words and follow the meaning pretty well. The reason you can do so is that you apply your knowledge of words to impose an understanding that the letters themselves do not otherwise give you.

Arocdnicg to rsceearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer are in the rghit pcale. The rset can be a toatl mses and you can sitll raed it wouthit pobelrm. Tihs is buseace the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

PERCEPTION

You probably think you see a white triangle below. There is no white triangle in the actual light that your eyes sense. There are only black shapes that have parts missing. You perceive a triangle by imposing that perception on the sensory data that your eyes are giving you.

You probably perceive the middle stimulus below (blue) differently on the first line than the second line, but it is exactly the same stimulus both times. Your eyes see the exact same data each time. So, the different perceptions on the two lines cannot be due to the stimulus itself. It has to be that the different perceptions are because you use the context to impose a different meaning on the two otherwise identical stimuli.

MEMORY

Since your initial perceptions of your world are already themselves in part due to top-down processing, then it follows that your memory of those perceptions may too be influenced by top down processing. But, it may also be that the act of recalling a memory may itself also involve more top-down processing. That is, when you recall an earlier experience, at the moment when you do the remembering you again impose meaning on your understanding. This type of process explains the fun of the party game where one person whispers a story into the ear of another person, and then that person whispers the story to another, and so on. At the end, the last person "remembers" a story that has been very much changed. I talk about several examples of top-down processing in memory in many of my presentations.