Attention and perception -- what we notice and perceive, and don't

"But did you notice the gorilla?"

Attention and perception may intuitively seem simple: you direct your attention at something and perceive it. But it can surprising how much we don't pay attention to or perceive, so let's dive into how attention and perception work a bit.

Selective attention is the type of attention you probably first thought about: it's when you focus on a specific thing, like your professor in a lecture, and disregard other information in your environment, like background noise and the visuals of the classmates all around you.

This attention is not always voluntary, though; rather, subjects of attention exist on a scale from automatically attracting your attention to requiring deliberate effort. If someone calls your name, you'll likely perk up and pay attention automatically. If your lecture is getting boring, on the other hand, you'll need to apply your willpower to stay focused.

This becomes apparent in the case of competing stimuli, such as the well-known Stroop effect: if asked to identify the color of a word, it's easy to make mistakes if the word says another color, for example the letters that spell out "green" presented in blue lettering. This is because you automatically pay attention to the word green, processing it faster than you can translate the color you perceive into a word.

Another subject of study in cognitive science is divided attention, when a subject juggles multiple cognitively difficult tasks, such as doing math and recalling a list of words simultaneously. For most people, performance on both tasks will decrease when attempted simultaneously. Some people, called "supertaskers" by Watson and Strayer (2010), don't experience this performance decrease; Medeiros-Ward et. al (2014) later found that these supertaskers had less activity in attention control areas of the brain, suggesting that they handle attention more efficiently on a neurological level.

Now what about perception? Just as attention is not as simple as straightforwardly focusing on something, perception is not as simple as simply sensing something, but rather involves synthesizing information from these senses. In this process, information from past experience plays a role (top-down processing) plays a role as well as the senses themselves (bottom-up processing).

For example, consider the following image (Terror Subterranea, Shepard, 1997):



Which of the running figures do you perceive as being bigger? You might already guess at what I'm getting at: the figures are actually the same size, but your prior understanding that objects in the distance appear smaller but are actually bigger affects your perception, making you perceive the figure in the back of the tunnel as bigger.

Perception can also combine with attention to create some jarring effects. The gorilla/monkey business video at the beginning is an example of inattentional blindness: when you center your attention on one specific aspect of the scene, you completely fail to notice unexpected elements that are obvious upon re-watching. Change blindness is another jarring phenomenon. The monkey business part of the video demonstrates this, as does a 1998 experiment by Simons and Levin where an unsuspecting test subject asked for directions by an actor did not notice when the actor was replaced by a completely different person following a distraction.