It’s tough to make predictions, especially about the future. ~Yogi Berra
brain is prediction machine — Locked inside your skull with no direct access to the world, it’s main job is to figure out the world and how to live in it. It does this by first building a model of the world from your sensory input from vision, hearing, smell, touch, taste, and from internal bodily sensors in joints, intestines, etc. But there are problems doing this because most of the sensory data never reaches our brain!
Through a Glass Darkly (Every Day)
Imagine you look at your class on the playground through a dirty window that blocks over 99% of the image. Your own vision system is actually worse than that (it’s actually very effective, given its limitations). The retina of your eye captures about ten billion bits each second when you look at your class, or the road ahead when you’r driving, or your teen’s messy bedroom. But only one millionth of that visual information actually reaches the first part of your brain that processes vision. A million times less than you way through the dirty window. Yet what you see looks sharp. How can this be?
Can The Jury Trust Your Eyewitness Testimony?
It gets worse. You are consciously aware of even less information coming from your eyes, but your brain gives you the illusion that you clearly see the reality in front of you. The brain’s magic is its prediction of what you should expect to see. You brain’s prediction is actually stronger that what you visually see. The famous illusion below demonstrates that your brain can over-rule your vision.
A Hot Date
All of your senses can be over-ruled by your predictions. Lisa Barrett recounts a personal example in her book How Emotions Are Made: The secret life of the brain (2017). On a first date over dinner, she felt her face flushing and her stomach fluttering as she chatted with her date. This resulted in a feeling of attraction to him, and this feeling stayed with her until she got home and promptly threw up. She actually had the flu. Her brain interpreted the sensory data from her body as attraction because it expected attraction to be a reasonable outcome of a dinner date. After her flu recovery, she realized that she wasn’t really attracted to her date at all. Her brain interpreted the flu symptoms through its model of a dinner date based on prior dinner date experiences. The field of psychology is filled with well-studied examples of your brain as a powerful prediction machine. While these two examples demonstrate prediction failures, remember that most of your brain’s predictions are completely accurate or at least appropriate. This prediction machinery is totally unconscious, so that it requires these failures to show how powerful and omnipresent our prediction machine actually is.
How You Get (and Spill) Your Coffee
Each of your normal movements are also predicted by your brain before the movement begins. If you reach for your cup of coffee, your brain has actually begun sending signals for the muscles in your arm to move about one third of a second before you know you want the coffee. During this process, your brain is “simulating” your arm reaching for and grasping the cup. The predictions and commands to move are based on this underlying simulation or “model” of how to achieve the task. All of this is unconscious, and it normally works exceptionally well with only occasional prediction errors that cause you to bump the coffee cup off the edge of the table. Our simulations and predictions are not perfectly accurate, but they are usually really good. They are “accurate enough.”
The Case of the Smiling Russian Student
We also simulate social behavior and predict actions that appropriate to each situation. When the social situation is unfamiliar, our predictions may be wrong. Sensing the prediction error, our brain can update its simulation of the situation. An example helps make this clear. Imagine the social situation of passing strangers on a sidewalk in Atlanta in the United States compared to the same situation in Moscow. It is customary for Americans to smile or somehow acknowledge the stranger, perhaps even saying “Hello,” “Good Morning,” or “How are ya.” Russians would pass the stranger without visual, expression, or verbal acknowledgement. There’s a Russian saying that captures this culture, “laughing for no reason is a sign of stupidity.“It’s a different culture, and the “expectations” of each person are normally those of their home culture. Russian students studying in the U.S. are initially shocked by all the smiles and small talk, and then they change their predictions to expect to engage in more “American” behavior. When they return to Russia, they may remark to their friends how their jaws ached for weeks with all the smiling. Our brains continually run unconscious simulations the internally define each social event, predict, and plan our appropriate behavior. We have an unconscious model of the world that we’ve been building since birth that runs as a continuous simulation. Our dreams at night have been categorized as simulations of expected future situations and our choices of actions to respond to them. These simulations of our future situations prepare us to deal with them thoughtfully (that’s “unconsciously thoughtfully”).