Surprising lapses in the way we process the world

Laurence Gonzales in Deep Survival. Page 71.

One of the reasons magic tricks work can be explained through a brain system called working memory. It is a general purpose workspace, and most of us experience it as attention or conscious thought. In addition, there are specialized systems for verbal and nonverbal information, and they have a type of short-term memory that allows perceptions to be compared with one another over the span of a few seconds. The general purpose area can take in information from the specialized systems (sight, smell, sound, and so on) and can integrate and process that information through what LeDoux calls "an executive function." That area of the brain, located mostly in the frontal lobes, is responsible for making decisions and voluntary movements, as well as directing what sensory input we're paying attention to. It's why we can still carry on a conversation in a room where many people are talking and music is playing. It's why we can choose between getting up and putting on a sweater or turning the thermostat up.

As LeDoux and others have explained, working memory can hold only a few things at once, perhaps half a dozen or so, and when something new commands attention, those things are forgotten. Working memory can also retrieve information from long-term memory. The fact that you can read this long sentence is the result of your working memory's ability to hold the beginning, the middle and end all at once and to retrieve definitions and associations from long-term memory and use them to make sense of the words. It is also the result of the fact that you have created mental models of the words. You don't read each letter to decode the word, as a child who is learning to read must. But if you come across words that are too similar, such as psychology and physiology, you may have to pause.

The fact that new information, especially emotionally charged information, forces things out of working memory means that we can't pay active attention to too many things at once. Unless something is successfully transferred from working memory into long-term memory, it is lost. We all have this experience when we try to memorize something that has no emotional content, such as an address or driving directions. In most people, the executive function can do one task at a time, and attempting to perform simultaneous tasks that involve a conflict begins to break it down. For example, if you flash the word "blue" printed in green ink on a screen for a second and then ask someone to say the word or the color, he'll have to stop and think before he answers.

The limited nature of working memory (attention) and the executive function, along with the shorthand work of mental models, can cause surprising lapses in the way we process the world and make conscious or unconscious decisions. That is why even experts can miss things that are right under their noses.