People high in neuroticism can make life difficult for themselves and for those who know them. Perhaps you’ve got friends or coworker who are always worrying about something, feels stressed most of the time, and tend to be in a bad mood. At the same time, you also notice that, even in casual conversation, they seem to be moving constantly, whether biting or picking at their nails, or shaking their legs. These repetitive behaviors, as it turns out, may very well be a function of their neurotic personalities. By the same token, if you don’t know someone’s personality very well but are trying to decide what he or she is like, the finger-biting and leg-shaking may tell you everything you need to know.
According to Atsushi Oshio, of Waseda University (Japan), these common bad habits of nail-biting and leg-shaking can actually be deleterious to people’s health. Nail-biting can lead to infection and leg-shaking, in Japan particularly, are considered highly undesirable. In other countries, leg-shaking may not have such significant social consequences, but they can tip other people off about the individual’s state of mind. Job interview advise websites warn against these giveaways about a candidate’s lack of confidence and perhaps even unstable personality. Oshio’s study is the only recent investigation attempting to link these bad habits with the Five Factor personality traits of Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness. As he notes, “such habits contribute to a feeling of disintegration instead of a unified and balanced feeling” (p. 1). Could research bear out this commonsense notion and show that there is an empirical basis for this speculation?
By way of background, the Waseda University researcher noted that nail-biting typically disappears as a behavior by the time people reach adolescence, though people may swap nail-biting for other repetitive behaviors (gum chewing and hair twirling). In cases when people don’t give up their nail-biting, they may fall into the diagnostic category of obsessive-compulsive and related disorders. Health-wise, nail-biting may also lead to severe damage to the cuticles and nails, and even dental problems. Leg-shaking occurs, according to Oshio, in almost half of Japanese adults, and almost an equal number want to rid themselves of this habit. As with nail-biting, leg-shaking may also become symptomatic of a psychological disorder such as Tourette’s (tic) syndrome, attention-deficit hyperactivity disorder, autism spectrum disorder, and Parkinson’s disease. On the positive side, though, leg-shaking may promote better health among people who have sedentary jobs.
Why people engage in these behaviors despite the health risks and violations of social norms becomes the next question, and according to Oshio they occur as a coping mechanism for stress, as an unconscious behavior that people physiologically can’t inhibit, or that the people engaging in them aren’t aware of the fact that the behaviors violate those social norms. The role of personality, as the focus of Oshio’s investigation, can also play a role as can age and gender.
The sample of 5328 Japanese adults (40% female with a mean age of 50) completed an Internet-based survey that also included questions about income, education, and body mass index. To test the behaviors of interest, Oshio asked participants to answer the following questions on a 5-point scale: 1. I am prone to shake legs, and 2. I am prone to bite nails. About half of the participants scored between a 2 and 4 on both of these scales with only about 2% receiving a score of 5 (strongly agree). To measure Five Factor personality traits, the Waseda researcher asked participants to complete a 10-item Japanese version of a measure validated by Gosling et al. (2003).
Because the key behavioral variables were not normally distributed, Oshio tested the personality-repetitive behavior relationship by comparing those who never engaged in the behavior with those who scored 2 or higher, indicating that they did engage in these behaviors. He also examined the contribution of age and gender to the personality-behavior relationship. The final statistical model based on predicting both nail-biting and leg-shaking from the predictor variables revealed that neuroticism had a stronger relationship to leg-shaking in males, and that extraversion had a stronger relationship to nail-biting in males than in females. Men high in introversion and low in agreeableness were also more likely to bite their nails, as were women high in openness. Additionally, there was a negative relationship between age and both behaviors, and in general, men were more likely than women to engage in both sets of behaviors.
Returning to the question of vulnerability to stress as a factor in nail-biting and leg-shaking, these findings suggest, according to Oshio, that men high in neuroticism are more prone to leg-shaking as a means of coping with stress. Men are less sensitive to social norms that inhibit women from engaging in these openly observable repetitive behaviors. As Oshio concluded, “there may be both neurophysiological and social norm processes controlling nail-biting behavior in males, while social norms are a stronger controlling factor than neurophysiological processes in female nail-biters.”
Given social norms against such show of emotions as nail-biting and especially leg-shaking in Japan, it would have been interesting to examine not just self-reports but also behavioral observations. Also, in a culture other than Japanese, with these social norms, the findings may have shown a stronger relationship between even self-reports and personality scale scores.
What can you learn, then, from this intriguing investigation? First, in addition to the many other cues that people use to gauge personality from body language, habitual behaviors can become an additional and important source. If you’re with a person you don’t know very well whose leg is shaking or who is picking at his (or even her) nails, you can conclude either that this person has a neurotic personality or that, alternatively, you’ve made this person nervous. Is there something you’re doing that’s causing the stress or anxiety? If your goal is not to make people uncomfortable, then you might want to ease back and be a little bit nicer. If, on the other hand, you’re trying to evaluate a person for a position in which it’s best to have a calm disposition, these behavioral signs might provide you with a note of caution.
Conversely, turn the mirror onto yourself. Are you habitually letting your body language leak out in these repetitive behaviors? You may be telling people more than you intend to about your inner state. Learning to control those behavior may be the first step to providing you with greater opportunities for fulfillment in your daily life.