A zero-acquaintance situation requires a perceiver to make a judgment about a target with whom the perceiver has had no prior social interaction. These judgments can be made using a variety of cues, including brief interactions with the target, video recordings of the target, photographs of the target, and observations of the target's personal environments, among others. In zero-acquaintance studies, the target's actual personality is determined through the target's self-rating and/or ratings from close acquaintance(s) of that target. Consensus in ratings is determined by how consistently perceivers rate the target's personality when compared to other raters. Accuracy in ratings is determined by how well perceivers' ratings of a target compare to that target's self-ratings on the same scale, or to that target's close acquaintances' ratings of the target. Zero-acquaintance judgments are regularly made in day-to-day life. Given that these judgments tend to remain stable, even as the length of interaction increases, they can influence important interpersonal outcomes.
Background
History The study of zero-acquaintance personality judgments developed from Cleeton and Knight's (1924) intent to demonstrate the futility of using physical criteria to predict unobservable individual traits. In order to accomplish this, Cleeton and Knight (1924) recruited 30 target participants from national fraternities and sororities, so that a large group of close acquaintances from these organizations could rate eight traits (i.e. individual traits included sound judgment, intellectual capacity, frankness, willpower, ability to make friends, leadership, originality, and impulsiveness) of the target participants. Cleeton and Knight (1924) then asked a group of strangers to rate these eight traits of each target participant after viewing the target participant from a distance for only a few minutes. After measuring several objective physical traits of the target participants, such as cranium size and eye width, Cleeton and Knight (1924) found that these physical traits were unrelated to close acquaintances' ratings of unobservable individual traits. However, they found that strangers' rating of an unfamiliar individual's traits were reliable; strangers tended to rate a target's personality similarly. Although these ratings were inaccurate, it became apparent that raters must be using similar indicators to make judgements about individual traits.
Passini and Norman (1966) found comparable evidence that strangers provide similar ratings of unobservable personality traits of a target participant with no prior acquaintanceship. In an introductory undergraduate psychology course, students with no previous interactions were placed into groups and asked to complete personality ratings for each member in the group. Given that the strangers tended to rate a target participant's personality similarly, Passini and Norman (1966) posited that some common observable characteristics must be informing these judgements. In the same year, Taft (1966) demonstrated that strangers can make judgments of personality more accurately than chance, but not as accurately as close acquaintances.
These findings went unnoticed for over twenty years, until Albright, Kenny, and Malloy (1988) revived interest and formally coined the term zero-acquaintance personality judgments. These researchers established that certain physical appearance variables, including attractiveness, type of dress (both formal and neatness), and perceived age, informed strangers' zero-acquaintance personality judgments. Ratings between strangers were most similar to each other and to the target's self-rating for the traits "sociable" and "responsible". Ratings of target attractiveness informed judgements of sociability; formality and neatness of dress informed judgements of responsibility.
Consensus in ratings
Consensus in zero-acquaintance studies refers to the degree to which multiple perceivers of a target make similar judgments of that target's personality traits. Even from a momentary interaction, multiple perceivers can come to the same conclusion about aspects of a person's personality. A few different explanations exist for this phenomenon. One such explanation is called similar meaning systems. This explanation posits that consensus arises when raters agree on the meaning of the information they use to make personality judgments. Some aspect of the individual (such as facial expressions or posture) appears to have the same meaning to each perceiver. For example, a smile or an erect stance might be an indicator of extraversion (one of the five traits in the five-factor model of personality to all perceivers, therefore these raters will all provide similar extraversion ratings. This does not necessarily mean that the ratings are accurate, just that all perceivers rated the individual similarly.
Stereotypes also influence consensus across perceivers. If perceivers of a target individual hold the same stereotypes about the target and use them in making personality judgments, consensus will be higher. For example, one gender may be stereotypically considered less emotionally stable than the other (neuroticism). Assuming perceivers hold this stereotype, they will make similar emotional stability ratings when the target's gender is known. Again, this does not assume that the stereotype is valid. In fact, some common stereotypes may prove to be invalid; use of such a stereotype by multiple perceivers will result in consistent, but inaccurate ratings (or high consensus and low accuracy).
It is worth noting that different personality traits show different levels of consensus. Of the traits in the Five Factor Model of personality, conscientiousness and extraversion tend to show higher levels of consensus, while agreeableness tends to demonstrate the least consensus. These patterns of findings suggest that some traits are more easily judged from brief interactions and more likely to be agreed upon than others. For example, facial expressions, which often indicate levels of extraversion, are easily detected in brief meetings, pictures, or video clips; perceivers tend to agree on what traits these facial expressions convey. Therefore, consensus tends to be higher for extraversion. Consensus can also result from beliefs about the target's physical attractiveness and traits commonly associated with attractive individuals. For example, extraversion is often associated with physical attractiveness. Because perceivers tend to agree on targets' physical attractiveness, consensus for extraversion is generally high.
Studies examining these differences in consensus across the Big Five traits have found that consensus ratings for extraversion tend to be around .27, compared to consensus of .03 for agreeableness. These numbers indicate how similarly raters view the same target's personality, with higher numbers indicating greater consensus for a particular trait. For agreeableness (with a consensus score of .03), there was virtually no agreement across raters of the target's level of agreeableness. For extraversion, (.27), there was much more consensus about the target's level of extraversion.
Studies have also examined the differences in consensus for zero-acquaintance raters and raters who have been long acquainted with the target. For extraversion, consensus ratings seem to be similar (.27 for zero-acquaintance and .29 for long-term acquaintance). For all other traits, long-term acquaintance ratings tend to converge much more than for zero-acquaintance ratings. For example, ratings of agreeableness demonstrate consensus estimates of .27 when long-term acquaintances are the raters, compared to .03 when there are zero-acquaintance raters. Those who are familiar with the target individual tend to agree about their personality traits much more than individuals who do not know the target, with the exception of extraversion. These study findings suggest that extraversion is a fairly observable trait for any person, whether they know the target or not, and people interpret social cues related to extraversion quite similarly.
Accuracy in ratings To determine if the perceiver in a zero-acquaintance context has made an accurate judgment of a target's personality, perceiver ratings are compared to the target's own ratings of their personality. The degree to which these two ratings converge is known as accuracy. Peer ratings (from people who have frequent contact with the individual being rated) can also be used to determine accuracy; if perceiver ratings of a target converge with peer ratings of the target, accuracy has been established. Accuracy is achieved when perceivers use what is known as "good information" about the target to make ratings. Information is "good" when it actually represents the trait being rated. For example, if a smile is actually reflective of extraversion, accuracy will be increased when perceivers use smiles to influence their extraversion ratings. This notion is known as the Realistic Accuracy Model (RAM; David C. Funder). When perceivers utilize good information in their ratings and ignore bad or irrelevant information, accuracy increases.
As mentioned above, both self-ratings and peer-ratings of a target can be used to calculate accuracy; in fact, several researchers suggest it is best to combine self-reports and peer reports when measuring accuracy (self-report inventory). This helps eliminate the flaws of each measure on its own and can increase confidence that the accuracy measure is itself accurate. This combined rating (usually an average of peer- and self-score) is then correlated with the zero-acquaintance perceiver ratings to determine accuracy, in what has been termed the "Gold Standard" in personality research;
Like consensus, accuracy is greater for some traits than others. In fact, a similar pattern to consensus exists, with extraversion and conscientiousness ratings tending to be the most accurate and agreeableness and openness ratings the least accurate of the five-factor model of personality. This is likely due to the trait-relevant information available to perceivers in zero-acquaintance settings. For example, in photographs there is more information present that accurately reflects conscientiousness and extraversion (such as cleanliness and facial expressions), than that which reflects agreeableness or openness.
Sociability-related traits have typically been found to be the easiest to judge when raters have little acquaintance with targets. Since extraversion largely measures social tendencies, it makes sense that the highest consensus and accuracy are found for this trait. Extraversion ratings by peer raters who had little interaction with targets demonstrated validities of .35, compared to validities of .01 for agreeableness. This stark difference in validity suggests that agreeableness is much harder to judge with accuracy when the rater is unfamiliar with the target. Conscientiousness has also demonstrated relatively high accuracy when the rater is unacquainted, with a validity of .29. The validity coefficient tells us how related the raters' judgments are to the target's own ratings of their personality. A validity coefficient of .35 (such as for extraversion) is fairly high, compared to a validity coefficient of .01, which indicates that there is absolutely no relationship between the two sets of ratings.
When raters are not very acquainted with the targets they are rating, it appears that the length of time they are actually able to