Self-control is also a key concept in the general theory of crime, a major theory in criminology. The theory was developed by Michael Gottfredson and Travis Hirschi in their book titled "A General Theory of Crime", published in 1990. Gottfredson and Hirschi define self-control as the differential tendency of individuals to avoid criminal acts independent of the situations in which they find themselves. Individuals with low self-control tend to be impulsive, insensitive towards others, risk takers, short-sighted, and nonverbal. About 70% of the variance in questionnaire data operationalizing one construct of Self-Control had been found to be genetic.