“Intuition comes very close to clairvoyance; it appears to be the extrasensory perception of reality.” -- Alexis Carrel
Intuition, or what is also known as instinct or gut feeling, can indeed phenomenally appear like it’s a kind of extrasensory perception of reality. Your boss is collecting donations for a Christmas present for the intern. As you are about to hand over your $50, you suddenly instinctively know that he is going to fail to convey that the joint gift is from everyone in the office. You are not sure how you came to that conclusion. You simply had a gut feeling, and you were right.
Although our gut feelings sometimes turn out to be right, it is not immediately clear whether they do in fact track reality. Lucky guesses also turn out to be right but there is no interesting causal connection between a guess and the external world.
Our gut feelings, however, are different from guesswork. They are the product of reliable heuristics and smart strategies the brain is already using to make quick decisions and estimates about what reality is like when time is of the essence. The brain has evolved to conserve its energy and speed up its computations through these kinds of shortcuts. Think about an outfielder during a game of baseball. It has long been a mystery how they can actually catch the ball. This certainly isn’t possible on the basis of conscious decision making, it’s too slow. It turns out that the brain doesn’t even bother calculating any real facts about the speed or trajectory of the ball. Instead, it uses an algorithm that adjusts the outfielder’s running speed so that the ball appears to continually move in a straight line in his field of vision. In other words, through practice, the outfielder’s brain has developed its own algorithm to make it possible for him to catch the ball. It’s a shortcut.
The brain is wired for shortcuts; these shortcuts help the unconscious brain make fast calculations when needed. Another common shortcut is to rely on perceptual expectations. For example, the brain makes predictions about the whereabouts of moving objects to enable us to see them. While the brain can unconsciously calculate the speed and position of very fast objects, it cannot do this in real time. When human eyes see an object like a speeding car, it takes one-tenth of a second for the brain to process that information. So, information that the brain receives from the eyes is already outdated by the time it reaches the visual cortex. To compensate for this, the brain makes estimations about where the object is going to be in the near future. The brain thus tracks moving objects as being farther along in their trajectory than what a person actually sees with their eyes. In this way, the brain can bypass the delay in processing time.
The brain also evolved to pick up on minute social cues in order to make predictions about the mental states and behavior of others. If you show a neurotypical four-year old an image of a person looking at a Hershey’s chocolate bar located next to a bag of M&Ms and a Reese’s peanut butter cup and ask which of the treats he or she is going to pick, the child will not hesitate before replying “the chocolate bar.” As we mature our abilities to unconsciously pick up on social cues and use them to determine our own behavior become more sophisticated. We learn to unconsciously detect deception and manipulation via facial expressions, eye gaze, bodily posture as well as past behavior. The product of this kind of unconscious detection is a gut feeling.
But our gut feelings clearly are not always good indicators of what the world is like. They sometimes misrepresent. So, how can we tell when there is a good chance that our gut feelings will be correct. How do we know when we might be better off using conscious reasoning or postponing making a decision rather than relying on our instinct? Generally, our gut feelings will tend to be reliable when the situation is similar to the environment in which the underlying heuristics evolved or developed.
The brain uses heuristics even when merely perceiving the world. What the brain expects us to see influences our perception of what we actually do see. But, of course, when the world is not as expected, we don’t see the world as it is. So, we are subject to a visual illusion. A good example of this phenomenon is the Müller-Lyer illusion (Fig. 1).
Figure 1 - The Müller-Lyer Illusion. Even when you learn that the line segments on the left have the same length, they continue to appear as if they have different length.
The direction of the arrowheads at the end of lines affects one’s perceptual experience: the line appears shorter when the arrowheads are turned inward, but longer when they are turned outward. The illusion persists even when we come to believe that the lines have the same length. We only see the lines as having the same length when we add vertical lines that allow us to compare their lengths.
There are several possible explanations of why the Müller-Lyer illusion occurs. The most popular explanation is based on depth perception (see Fig. 2). Depth perception involves generating an internal three-dimensional model of the environment. Part of the mechanism that produces the three-dimensional model adjusts for the sameness in size of objects located at different distances from us. This is also known as “size constancy.” This mechanism ensures that objects are not perceived as shrinking when we move away from them. As a result of this process, the brain projects the retinal image of the outward hashes to what would normally be its correct distance in our internal model, thus making the line segment with the outward hashes seem longer.
Figure 2 - The Müller-Lyer Illusion: Illustration of how outside corners generate the appearance of the object being further away from us, whereas inside corners generate the appearance of the object being closer to us.
In the case of the Müller-Lyer illusion the environment is not at all similar to the environment in which our abilities to perceive depth evolved, so our gut feeling that the line segments have different length fails to track reality.
With a bit of care in deciding whether or not to trust our guts, however, we can use this brilliant adaptive trait to reliably navigate the physical and social worlds.