Assimilation reflects the extent to which a perceiver rates targets in the same way; using the Social Relations Model, assimilation is assessed by the degree of perceiver variance and is typically measured as the proportion of the total variance due to the perceiver. This proportion can be interpreted as the correlation of two ratings by the same perceiver of two different targets.
The question concerns whether the perceiver sees the targets the same. More colloquially does the perceiver think that the "targets all look alike"? Note that if all of the perceivers see the targets in the same way, there is not assimilation. Assimilation requires that one perceiver see the targets in one way and another perceiver see the targets in another way. Finally, note that assimilation refers to the targets also. So if the judgments are same-gendered, the degree of assimilation refers to same-gendered partners. Different results might be obtained the partners were members of the other gender.
Key Results (most all of these results are going to be in the new edition of Interpersonal Perception)
The average level of assimilation is about .25 in judgments of the Big Five which means that the perceiver effect explains about twenty-five percent of the variation in the perception of others. Alternatively it can be viewed as the correlation between a perceiver's ratings of two targets is .25. For liking the level of assimilation is a typically somewhat higher.
Variation across Traits and Contexts
Assimilation is less for more observable traits (e.g., Extroversion), especially when they are highly evaluative (Kenny & West, 2010).
Assimilation appears to decline with increasing familiarity, which is consistent with view that the perceiver effect represents a guess of what others are like. For liking judgments, assimilation may in fact increase due to changes in how much the person likes being in the group.
Assimilation tends to be greater for judgment of members of out-groups than it is for in-groups (Boldry & Kashy, 1999). Assimilation is greater in computer-mediated interactions and in groups more than one-on-one interactions.
There is some evidence that the perceiver effect is related to gender (Winquist, Mohr, & Kenny, 1998 ). Also it has been shown the perceiver effects are greater those who are securely attached, not depressed, and not narcissistic. All of these effects are rather small, correlations of no more than .20.
Consistency across Traits
Both Wood and colleagues (2010) and Srivastava and colleagues (2010) have found that the perciever effect is strongly correlated across the Big Five. Most, but not all of that covariation is determined by positivity: Some perceivers genrally see targets positively and others genrerally see targets negatively. In part this reflects more of tendency to like members of the particular group being judged, not a general tendency to like members of all groups. Moreover, there are some reasons to believe part of the positivity effect reflects one's transient mood.
Once positivity is removed, there are some trait specific perceiver effects, what was called personal stereotype in the Interpersonal Perception book.
Srivastava and colleagues (2010) also find evidence for a relatively weak acquiescence effect or the tendency to give high (or low ratings) to all targets.
Consistency across Time
Assimilation tends to be fairly stable over time. Several studies show increasing consistency over time and Wood and colleagues found a one-year stability of .69. For shorter intervals once perceivers get to know the targets the stabilities can be as high as .80. However, the evidence, as reviewed by Kenny (1994), judgments made at zero acquaintance show much lower levels of stability of 64.
Consistency over Different Classes of Targets
Here the question concerns whether the perceiver effect for one group of targets (e.g., friends) is the same as the perceiver effect for a different group of targets (e.g., co-workers) The perceiver effects for in-group and out-group members are positively correlated, but the correlation is relatively weak for liking judgments. Data from Malloy and colleagues (1997) finds consistency in the perception of family members, co-workers, and friends, correlations of about .51. Finally, in perhaps one of the strangest interpersonal perception study ever conducted, Kwan, Gosling, and John (2006) find that the perceiver effect is correlated across the perception of other people and dogs, r = .56. People and dogs are seen as more similar than different types of people.
Chapter 3 of Kenny's 1994 Interpersonal Perception: A Social Relations Analysis.
Boldry, J. G., & Kashy, D. A. (1999). Intergroup perception in naturally occurring groups of differential status: A social relations perspective. Journal of Personality and Social Psychology, 77, 1200-1212.
Kenny, D. A., & West, T. V. (2010). Similarity and agreement in self- and other perception: A meta-analysis. Personality and Social Psychology Review, 14, 196-213.
Malloy, T. E., Albright, L., Kenny, D. A., & Agatstein, F. (1997). Interpersonal perception and metaperception in nonoverlapping social groups. Journal of Personality and Social Psychology, 72, 390-398.
Kwan, S. Y., Gosling, S. D., & John, O. P. (2006). Anthropomorphic projections of personality: A cross-species Social Relations Model Analysis of humans and dogs. Unpublished paper, Arizona State.
Srivastava, S., Guglielmo, S., & Beer, J. S. (2010). Perceiving others’ personalities: Examining the dimensionality, assumed similarity to the self, and stability of perceiver effects. Journal of Personality and Social Psychology, 98, 520-534.
Winquist, L. A., Mohr, C. D., & Kenny, D. A. (1998). The female positivity effect in the perception of others. Journal of Research of Personality, 32, 370-388.
Wood, D., Harms, P., & Vazire, S. (2010). Perceiver effects as projective tests: What your perceptions of others say about you. Journal of Personality and Social Psychology, 99, 174–190.
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