It may not be possible to judge a book by its cover, but judging someone by the contents of their iTunes library could be a very different story, new research suggests.

Dr Jason Rentfrow is a Psychologist at the University of Cambridge, and Lecturer in Psychology in the Department of Social and Developmental Psychology. He just finished a research project at the University that revealed that many of us use musical taste both as a means of expressing our own identity, and a means to form and refine our opinions about other people.

Dr. Rentfrow’s research team found that sample groups of subjects make assumptions about people’s personalities, values, social class and even their ethnicity, based on their musical preferences.

Rock fans, for instance, are commonly held to be rebellious and artistic, but emotionally unstable. Classical music-lovers, on the other hand, are seen as personable and intellectual, but unattractive and a bit boring.

There have been interesting results from this study.  They show that music is a powerful form of social expression that can reinforce stereotypes and, potentially, social prejudices. By stating a preference for a musical style, many people appear to use music as a “badge” to tell others about their personality and values.

Dr. Rentfrow said the following about his research results.

“Humans, as social beings, develop techniques that help them to predict what another person is going to be like from the moment they first meet.  Because we can’t carry out a full psychological assessment on the spot, we ask them questions which help us to build up a picture of their personality. This research suggests that, even though our assumptions may not be accurate, we get a very strong impression about someone when we ask them what music they like.”

Dr Rentfrow asked the participants to consider six broad genres – rock, pop, electronica, rap, classical and jazz. No definition of the genre was given beyond its name as the researchers were interested in the assumptions that people would make.  The profiles for each genre were both consistent and differed sharply from one another, suggesting that the stereotypes are both clear-cut and firmly held by many subjects.

Jazz fans, for example, were viewed as friendly, emotionally stable people with a limited sense of responsibility. Rap fans were viewed as more hostile, but were seen as energetic and athletic. Classical music was linked to white, upper-class people and rap to black or mixed black people from lower class backgrounds. Those with a preference for rock songs are deemed to be “natural rebels”, thoroughly irresponsible and emotionally unstable, while pop fans are seen as conventional and calm but lacking in intelligence and wisdom. All six styles were associated with middle class people.

The study suggests that while these stereotypes may not be true, they do mean that people are making clear statements about their self-image and their personality when they discuss their favorite bands or composers. The researchers also found that the way in which these genres are portrayed by artists and in the media appears to reinforce, and therefore perpetuate, such stereotypes.

“It is now common practice to list your favorite bands on sites like MySpace or Facebook,” Dr Rentfrow added. “This research shows that in doing so, many of us are also making clear public statements of who we are and how we should be perceived, whether we are conscious of that or not.”

What stereotype do we portray if our iPod is filled with music by Clay Aiken?  Maybe Rentfrow’s research about Pop fans shocked Clay into deciding to perform all genres of music.  Who would want to be saddled with fans that are “conventional and calm but lacking in intelligence and wisdom.”

What is on your iPod?  Does it fit your musical image?