Perception and thinking

Perception is how the brain organizes and interprets sensations. In bottom-up processing, we build a perception from the raw details. In top-down processing, knowledge and expectations guide what we perceive. A perceptual set is a readiness, shaped by context or experience, to see something a certain way.

The brain groups what it sees by Gestalt principles such as figure and ground, proximity, similarity and closure. It judges depth with binocular cues that need both eyes, such as retinal disparity and convergence, and with monocular cues such as relative size, interposition, linear perspective and texture gradient. Perceptual constancy lets us see a door as the same shape and size as it swings open.

Attention is limited. In inattentional blindness, we miss a visible object because attention is elsewhere. In change blindness, we miss a change between one view and the next.

Thinking uses concepts and prototypes, the best example of a category. To solve problems we use algorithms, step-by-step methods that guarantee an answer, or heuristics, fast shortcuts. The availability heuristic judges likelihood by how easily examples come to mind. The representativeness heuristic judges by how well something fits a typical case. Other pitfalls include confirmation bias, mental set (sticking with a method that worked before), functional fixedness (seeing an object only in its usual use), belief perseverance and overconfidence. The framing effect is when the wording of a choice, such as gains versus losses, changes the decision.

To explain a thinking error, name it and then point to the exact behavior in the scenario that shows it. Say what the person relied on, such as an easy-to-recall example, and what they ignored, such as how common something really is.