In psychology, temperament refers to those aspects of an individual's personality, such as introversion or extroversion, that are often regarded as innate rather than learned. A great many classificatory schemes for temperament have been developed; none, though, has achieved general consensus in academia.

Historically, the concept of temperament was part of the theory of the four humours, with their corresponding four temperaments. The concept played an important part in pre-modern psychology, and was explored by philosophers such as Immanuel Kant and Hermann Lotze. David W. Keirsey also drew upon the early models of temperament when developing the Keirsey Temperament Sorter. More recently, scientists seeking evidence of a biological basis of personality have further examined the relationship between temperament and character (defined in this context as the learnt aspects of personality). However, biological correlations have proven hard to confirm.

Temperament is determined through specific behavioural profiles, usually focusing on those that are both easily measurable and testable early in childhood. Commonly tested factors include irritability, activity, frequency of smiling, and an approach or avoidant posture to unfamiliar events. There is generally a low correlation between descriptions by teachers and behavioural observations by scientists of features used in determining temperament.

Jerome Kagan is an American psychologist. He was born in 1929 in Newark, New Jersey, and grew up in Rahway, New Jersey. Kagan is currently retired after being a professor at Harvard University in the Developmental program. He is one of the key pioneers of developmental psychology. He is Daniel and Amy Starch Research Professor of Psychology, Emeritus at Harvard University, and co-faculty at the New England Complex Systems Institute. He has shown that an infant's "temperament" is quite stable over time, in that certain behaviors in infancy are predictive of certain other behavior patterns in adolescence. He did extensive work on temperament and gave insight on emotion.

Kagan was listed as the 22nd most eminent psychologist of the 20th Century, just above Carl Jung.

Steven Siro Vai (born June 6, 1960) is an American guitarist, songwriter and producer who has sold over 15 million albums. After starting his career as a music transcriptionist for Frank Zappa, Vai recorded and toured in Zappa's band for two years, from 1980 to 1982. He began a solo career in 1983, has released eight solo albums and won three Grammy Awards. He has also recorded and toured with Public Image Ltd., Alcatrazz, David Lee Roth and Whitesnake. Vai has been a regular touring member of the G3 Concert Tour which began in 1996. In 1999 Vai started his own record label Favored Nations, intending to showcase as he describes, "...artists that have attained the highest performance level on their chosen instruments."

Vai began playing guitar in 1973, at the age of 13. In 1974, he took guitar lessons from guitarist Joe Satriani and played in local bands, one of which was called "The Steve Vais". He was influenced by guitarists including Jimi Hendrix, Jeff Beck, Brian May, Jimmy Page, Glen Buxton, and jazz fusion guitarist Allan Holdsworth. Vai attended the Berklee College of Music, afterwards recording a promotional piece for them in which he spoke about auditioning for Frank Zappa at age 20.