4.2: Perception is Selective

Last updated
Save as PDF

Page ID: 95027

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

Filtering and Selection

There is a lot going on in the world around us. But we aren’t constantly overwhelmed by sensory overload, because perception is selective. Some of the selection and filtering occurs at the neural level. For example, the human visual system is only sensitive to a small band of the electromagnetic spectrum, in the interval between ultraviolet and infrared electromagnetic radiation. We can’t see information conveyed by X-rays (like the people in science fiction stories who can see through walls) or by infrared light (unless we wear special goggles, like those that allow us to make out shapes at night). Similarly, we can’t hear the high-pitched sounds dogs can hear, or make sense of the intricate pattern of shrieks emitted by bats to navigate in the dark.

Attention: Further Filtering

Some perceptual selectivity is “hard-wired,” but some also depends on our beliefs, emotions, desires, and other factors that aren’t part of our in-born physiology. When you enter a large room full of noisy people, it’s just a loud din. But once you strike up an interesting conversation with someone, you tune out most of the noise around you and focus on them. You have no idea what people across the room are saying – until one of them mentions your name. Then, all of a sudden, their words leap out at you.

Experiments show that this sort of phenomenon is common. We filter out a lot of information, but when it is relevant to us, we often tune it back in. Some of the factors that lead us to focus on some things while ignoring others – things like expectations and emotions and desires – bear on our topic of reasoning, but here we will focus on an even more direct connection.