What perceptual set means

1. Perceptual set is a readiness to perceive some things and to ignore others.
2. It is at work before you are aware of it, so you pick up what you are primed for and skim past the rest.
3. It matters most when the input is brief, blurred or ambiguous, because that is when your readiness rather than the stimulus decides what you report.
4. Four influences build a set: motivation, expectation, emotion and culture.

Motivation

1. A strong need or drive makes you quicker to perceive whatever might satisfy it.
   1. Hunger makes food words and cooking smells on a high street jump out at you while the other shop signs blur past.
2. Motivation also lowers the threshold for noticing, so a weaker or briefer signal is enough to be perceived.

Expectation

1. What you have been led to expect shapes what you actually perceive.
   1. Told that you are about to be shown an animal, you read an ambiguous sketch as an animal rather than as a face.
2. Expectation can come from a label, from the instructions you are given, or simply from the material sitting around the thing.
   1. One shape reads as the number 13 in a row of numbers and as the letter B in a row of letters, although the ink is identical.

Emotion

1. Your feelings bias you towards some things and away from others.
   1. Anxious about a result, you catch the word fail in a page you have barely scanned.
2. Strong emotion can also work the other way, slowing down the perception of something you would rather not see.

Culture

1. The environment you grow up in trains you to interpret scenes in particular ways.
   1. Someone raised among straight-edged buildings and rectangular rooms reads depth into a flat drawing differently from someone raised where those shapes are rare.
2. Culture also supplies the labels and categories you think with, and those decide which reading of an ambiguous image comes to you first.

When the influences pull together

1. In real life the four rarely act alone, and they stack on top of one another.
2. A hungry, anxious visitor in an unfamiliar city is pulled by motivation, emotion and culture all at once.
3. They can also pull against each other, so a strong enough emotion can override what you had been told to expect.

Evidence that set changes what people report

1. Carmichael, Hogan and Walter (1932) gave people one of two names for each of twelve ambiguous figures before they saw them, then asked them to reproduce the figures.
   1. Among the reproductions that had changed most, 74 per cent from one list and 73 per cent from the other resembled the name that had been given, against 45 per cent in a control group who saw the figures unnamed.
2. Haber and Levin (2001) found that people estimated the sizes of familiar objects about as accurately from memory as they did with the objects in view.
   1. What you already know about an object is therefore doing real work in how you perceive it.

Turning this into marks

1. Name the influence and then show how it changed what the person in the scenario reported seeing.
2. Say why that influence primes that particular perception, because an example on its own is not an explanation.
3. The mark most often lost is naming all four influences without applying any of them to the scenario.