How many slices does it take to accurately judge personality and intelligence?

ResearchBlogging.orgSuppose your organization is interviewing candidates for an important job. Would it be better for one trusted person to have an extended interview with them, or for several people to talk to them for less time? How many people would you need to conduct the interviews? Would three be enough? Would ten be too many? If ten is good, wouldn't twenty be even better?

We've discussed thin-slicing studies before -- the idea that a few brief exposures to an individual can give just as accurate an impression of key traits as much more extended interactions. For judging sexual preference in men, a 10-second exposure to pictures of faces isn't any better than a 50-millisecond exposure. For evaluating teaching ability, a few 10-second movie clips are nearly as good as an entire semester in class.

But these studies didn't vary the number of times judges were exposed to the images or video clips. Could seeing more small bits of information about an individual could help people make more accurate judgments? A team led by Peter Borkenau recognized that the vast quantities of data collected in the 1990s for the German Observational Study of Adult Twins (GOSAT) could be used to answer that question. The GOSAT recruited 300 pairs of twins, who underwent detailed personality and intelligence testing, and were also extensively interviewed and videotaped. Borkenau's team wasn't interested in the twins' similarities and differences, so they analyzed the data twice, once for each group of 300 unrelated individuals, then averaged the results together.

Each twin's personality was also rated by two acquaintances, the experimenter who guided their session, and a confederate who had participated in six videotaped sessions with them. The twins were videotaped for a total of fifteen sessions, doing things like introducing themselves, recalling objects they had just seen, telling jokes, and reading newspaper headlines.

Each these 15 video clips were then shown to judges who rated them on 20 personality traits and intelligence, using a five-point scale (e.g. 1 = "unintelligent" and 5 = "intelligent"). Each judge saw only one clip from each individual, and each clip was viewed by four judges. Altogether, 1.26 million ratings were made by the judges. So does the rating of just one clip of an individual correlate to that person's actual personality score from the personality tests? Yes it does, but the strength of the correlation varies depending on what trait is being measured. This graph shows the results:


The horizontal axis shows the number of different clips being analyzed, while the vertical axis shows the correlation between the judges' ratings of personality categories and the individual's actual score on the personality test. So when just one clip was shown, there was a correlation, but it was quite low -- less than .05 for "conscientiousness," and .21 for the best correlation, "extraversion." The researchers then randomly selected additional judges' reports to average together for viewings of multiple clips. So for 2 clips, you're looking at an average of the ratings for a variety of different combinations of judges' ratings -- joke-telling and introductions, or object recall and headline-reading, for example. And as you might expect, the correlations get stronger as more clips are analyzed. But once about 6 clips are analyzed, the correlation doesn't get significantly stronger. There doesn't appear to be much reason for the judges to watch more than 6. It's important to point out that even the strongest correlations here aren't especially strong. A correlation of .3 is probably best characterized as "moderate," and acquaintances did better, averaging about a .45 correlation with the twins' personality test results.

But remember, judges also were asked to rate the apparent intelligence of the participants, who had also taken two different intelligence tests. This graph shows how well the judges' scores compared to the actual test scores:


APM and LPS are simply two different types of intelligence tests. These correlations are stronger than the correlations for personality -- the correlation between judges' ratings and actual test scores reached .53 for the LPS test. However, test scores were also correlated with gender and age. Once these effects were controlled for, the LPS correlation dropped to .46 -- still a moderately strong correlation.

As with the personality measures, once the ratings of more than six clips were combined, there wasn't much of an improvement in the correlation between the test scores and the ratings.

So using a bunch of judges to watch short clips of behavior can be a good way to judge personality and attention -- but only up to a point. Once you exceed six judges, there isn't much improvement. And watching these thin slices of behavior doesn't work as well for every personality trait: while it works pretty well for intelligence, it's not so useful for judging conscientiousness. In our hypothetical job-interview situation, you'd probably be better off just checking the candidates' references than making a guess based on what you see in the interview.

Borkenau, P., Mauer, N., Riemann, R., Spinath, F., & Angleitner, A. (2004). Thin Slices of Behavior as Cues of Personality and Intelligence. Journal of Personality and Social Psychology, 86 (4), 599-614 DOI: 10.1037/0022-3514.86.4.599

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Enjoyed this and certainly supports my own view about early impressions after nearly 30 yrs of clinical practice.
I too use the 'Big Five' as a standard in calibrating patient and student types.

i am a retired Experimental Psychologist in INDIA.
The information here is clear, reliable and very useful to me.

By very useful in… (not verified) on 21 Dec 2009 #permalink

This article is useful, however, the lead in that cites the study about how teachers are "accurately" rated by only a few clips is VERY misleading. The only thing that study shows is that students are probably superficial and that they maintain their first impression throughout a semester. It is especially disheartening that the connected article isn't even a citation of the original study, but rather a poorly thought out article that cites the original study.

I should probably look at the study on judging sexual preference, but I'm not sure that a study on judging sexual preference from brief exposure should be compared to judging personality or intelligence from brief exposure. Sexuality is a whole different beast of denial and innuendo.

And, since people are eagerly sharing their credentials here: I was rejected from grad. school in clinical and social psychology about 5 years ago. Perhaps this article sheds some light on why? Probably not. I tend to seem much more agreeable in an interview than I actually am in real life!

The Existential Psychoanalytic Institute of Seattle is a contemporary psychoanalytic society, research institute, and clinic dedicated to the exploration and treatment of the human condition through a synthesis of existential analysis, traditional psychoanalysis, phenomenology, and critical philosophy.