Assimilation and contrast effects

Assimilation and contrast effects describe cognitive biases in how individuals perceive and evaluate stimuli based on contextual information. The assimilation effect, also known as assimilation bias, occurs when people judge something as closer to what’s around it, making it blend in with its context. In contrast, the contrast effect happens when people see something as farther apart from its surroundings, highlighting differences instead. These effects are widely studied in psychology and influence how we form opinions, make decisions, and view others. For example, if a student scores 85% on a test in a class where everyone else scores around 90%, the grade might seem worse due to contrast, but if the class average is 70%, the same 85% might feel more impressive because of assimilation.

History and definition

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.