Not only do absolute thresholds vary from person to person, they also vary from time to time for a single person. The type of stimulus, the state of one’s nervous system, and the costs of false “detections” all make a difference. Emotional factors are also important. Unpleasant stimuli, for example, may raise the threshold for recognition. This effect is called perceptual defense. “Dirty” words took longer to recognize when flashed on a screen that did “clean” words. Apparently it is possible to process information on more than one level and to resist information that causes anxiety, discomfort, or embarrassment (Dember & Warm, 1979).

In other words, the tendency of perceivers to protect themselves against ideas, objects, or people that are threatening to them is called perceptual defence. It is a function of selective perception which protects the individual from threatening or contradictory stimuli” (1992, 160). “Perceptual defence occurs when a person’s value orientations act as a barrier to stimuli that are threatening” (Runyon, 1977, 300). For example, an alcoholic may avoid anti-drinking and driving campaigns in fear of what could happen because they know they drink and drive sometimes. They fear what could possibly happen if they actually accepted the message

In case of consumer, perceptual defence can cause them to avoid or misinterpret otherwise important messages. It can occur under the following conditions (Assael, 1992, 142):

  • When consumers have strong beliefs and attitudes about a brand. If the message does not conform to what they believe, they are less likely to perceive. If someone sees an ad for vegetables, they may choose to ignore it if they eat fast food every day.
  • When consumers have consistent experience with a brand. Brand-loyals are less likely to switch, regardless of how much “better” another product is.
  • When anxiety is produced by a stimulus. If an overweight person sees an ad for Weight Watchers or a gym, they may disregard the message because that stimuli produces fears and anxieties.
  • When there is a high level of postpurchase dissonance. Consumers will search out positive information about a brand after they have purchased that brand and they will ignore the negative information

Cognitive Dissonance Theory

It may be defined as the feeling of uncomfortable tension which comes from holding two conflicting

thoughts in the mind at the same time.

Dissonance increases with:

  • The importance of the subject to us.
  • How strongly the dissonant thoughts conflict.
  • Our inability to rationalize and explain away the conflict.

Dissonance is often strong when we believe something about ourselves and then do something against that belief. If I believe I am good but do something bad, then the discomfort I feel as a result is cognitive dissonance. Cognitive dissonance is a very powerful motivator which will often lead us to change one or other of the conflicting belief or action. The discomfort often feels like a tension between the two opposing thoughts.

To release the tension we can take one of three actions:

  • Change our behaviour.
  • Justify our behaviour by changing the conflicting cognition.
  • Justify our behaviour by adding new cognitions.

Dissonance is most powerful when it is about our self-image. Feelings of foolishness, immorality and so on (including internal projections during decision-making) are dissonance in action.

If an action has been completed and cannot be undone, then the after-the-fact dissonance compels us to change our beliefs. If beliefs are moved, then the dissonance appears during decision-making, forcing us to take actions we would not have taken before. Cognitive dissonance appears in virtually all evaluations and decisions and is the central mechanism by which we experience new differences in the world. When we see other people behave differently to our images of them, when we hold any conflicting thoughts, we experience dissonance. Dissonance increases with the importance and impact of the decision, along with the difficulty of reversing it. Discomfort about making the wrong choice of car is bigger than when choosing a lamp.


Festinger first developed this theory in the 1950s to explain how members of a cult who were persuaded by their leader, a certain Mrs Keech, that the earth was going to be destroyed on 21st December and that they alone were going to be rescued by aliens, actually increased their commitment to the cult when this did not happen (Festinger himself had infiltrated the cult, and would have been very surprised to meet little green men). The dissonance of the thought of being so stupid was so great that instead they revised their beliefs to meet with obvious facts: that the aliens had, through their concern for the cult, saved the world instead. In a more mundane experiment, Festinger and Carlsmith got students to lie about a boring task. Those

who were paid $1 felt uncomfortable lying.


Smokers find all kinds of reasons to explain away their unhealthy habit. The alternative is to feel a great deal of dissonance.

Social Nature of Perception

Social nature of perception relates to how people look at themselves and others. There are two effects that are worth mentioning while talking about social nature of perception:

1) Stereotyping

Stereotypes are generalizations, or assumptions, that people make about the characteristics of all members of a group, based on an image (often wrong) about what people in that group are like. For example, one study of stereotypes revealed that Americans are generally considered to be friendly, generous, and tolerant, but also arrogant, impatient, and domineering. Asians, on the other hand, were expected to be shrewd and alert, but reserved. Clearly, not all Americans are friendly and generous; and not all Asians are shrewd. If you assume you know what a person is like, and don’t look at each person as an individual, you are likely to make errors in your estimates of a person’s character.

The word stereotype was invented by Firmin Didot in the world of printing; it was originally a duplicate impression of an original typographical element, used for printing instead of the original. American journalist Walter Lippmann coined the metaphor, calling a stereotype a “picture in our heads” saying “Whether right or wrong, …imagination is shaped by the pictures seen… Consequently, they lead to stereotypes that are hard to shake.” (Public Opinion, 1922, 95-156). To note, cliché and stereotype were both originally printers’ words, and in their literal printers’ meanings were synonymous. Specifically, cliché was a French word for the printing surface for a stereotype.

In conflicts, people tend to develop overly-negative images of the other side. The opponent is expected to be aggressive, self-serving, and deceitful, for example, while people view themselves in completely positive ways. These stereotypes tend to be self-perpetuating. If one side assumes the other side is deceitful and aggressive, they will tend to respond in a similar way. The opponent will then develop a similar image of the first party, and the negative stereotypes will be confirmed. They may be grow worse, as communication is shut down and escalation heightens emotions and tension.

When we consider a person good (or bad) in one category, we are likely to make a similar evaluation in other categories. It is as if we cannot easily separate categories. It may also be connected with dissonance avoidance, as making them good at one thing and bad at another would make an overall evaluation (which we do anyway) difficult. Edward Thorndike found, in the 1920s, that when army officers were asked to rate their charges in terms of intelligence, physique, leadership and character, there was a high cross-correlation. Just because I dress like a rock star, it does not mean I can sing, dance or play the guitar (come to think of it, the same is true of some real rock stars!).

2) Halo effect

The halo effect refers to a cognitive bias whereby the perception of a particular trait is influenced by the perception of the former traits in a sequence of interpretations.

The halo effect is involved in Kelley’s implicit personality theory, where the first traits we recognize in other people then influence the interpretation and perception of latter ones (because of our expectations). Attractive people are often judged as having a more desirable personality and more skills than someone of average appearance. Celebrities are used to endorse products that they have no expertise in evaluating.

When commanding officers were asked to rate their soldiers in an early psychology experiment conducted by Edward L. Thorndike, he found high cross-correlation between all positive and all negative traits. People seem to rarely think of each other in mixed terms; instead we seem to see them as universally roughly good or roughly bad across all categories of measurement. Solomon Asch also performed research in this area. The halo effect may be involved with the theory of cognitive dissonance. Solomon Asch has also done a study about central traits and his findings suggest that attractiveness is a central trait, so we presume all the other traits of an attractive person are just as attractive and sought after. Individuals often exhibit their best behavior in the presence of authority figures, presumably to avoid being accosted by said figures.

The halo effect is also a term used in HR recruitment. While interviewing a person, you might be influenced by one of his attributes and ignore his/her other weaknesses.

Subliminal Nature of Perception

Anytime information is processed below the normal limen (threshold or limit) for awareness, it is subliminal. Subliminal perception was demonstrated by an experiment in which people saw a series of shapes flashed on a screen for 1/1000 second each. Later, they were allowed to see these shapes and other  “new” shapes for as long as they wanted. At that time, they rated how much they liked each shape. Even tough they could not tell “old” shapes from “new,” they gave “old” shapes higher ratings (Kunst-Wilson & Zajonc, 1980). It seems that the “old” shapes had become familiar and thus more “likable,” but at a level below normal awareness. To summarize, there is evidence that subliminal perception occurs. However, well-controlled experiments have shown that subliminal stimuli are basically weak stimuli. Advertisers are better off using the loudest, clearest, more attention-demanding stimuli available –as most do.


  • Self-Perception Theory gives an alternative view:
  • Asch, S. E. (1946). Forming impressions of personality. Journal of Abnormal and Social Psychology, 41, 258-290
  • Thorndike, E. L. (1920). A constant error on psychological rating. Journal of Applied Psychology, IV, 25-29
  • Kelly, G. A. (1955). The psychology of personal constructs (Vols. 1 and 2). New York: Norton.
  • S5cial Psychology Network Stereotyping:
  • Dr. Sam Vaknin. The Merits of Stereotypes:
  • Media Awareness Network. What is a stereotype? Definition, role of stereotyping in the media:
  • Halo effect – Wikipedia, the free encyclopedia The halo effect refers to a cognitive bias whereby the perception of a particular:
  • Self-Perception Theory gives an alternative view.

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