Assimilation and contrast effects

The assimilation effect, assimilation bias or biased assimilation is a bias in evaluative judgments towards the position of a context stimulus, while contrast effects describe a negative correlation between a judgment and contextual information.

Francis Bacon (1561 – 1626) is quoted to have written "The human understanding when it has once adopted an opinion ... draws all things else to support and agree with it."

In 1979, psychologists speculated about the mechanisms of biased assimilation in that one gives "any information that suggests less damaging ‘alternative interpretations’" such importance to use it as proof for one´s belief. The classic Stanford University experiment involved supporters and opponents of the death penalty. After showing participants a study that concluded it deterred crime and another suggesting the opposite, they rated the study contradicting their beliefs as poor quality and not persuasive, so that the information resulted in more attitude polarization.

In 2004 it has been defined as a bias in evaluative judgments towards the position of a context stimulus. In an assimilation effect, judgment and contextual information are correlated positively, i.e. a positive context stimulus results in a positive judgment, whereas a negative context stimulus results in a negative judgment.

Assimilation effects are more likely, when the context stimulus and the target stimulus have characteristics that are quite close to each other. It is the power of narratives in fueling a certain belief. In priming experiments published in 1983, Herr, Sherman and Fazio found assimilation effects when subjects were primed with moderate context stimuli. Depending on how the individual categorizes information, contrast effects can occur as well. The more specific or extreme the context stimuli were in comparison to the target stimulus, the more likely contrast effects were to occur.

The term assimilation effect appears in the field of social comparison theory as well. Complementary to the stated definition, it describes the effect of a felt psychological closeness of social surroundings that influence the current self-representation and self-knowledge.

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