Biological studies

Brain areas

Lonstein and Stern 1998, lesions to PAG in recent mother rats = aggression unfamiliar males.

Phineas Gage.

Mitchell et al. 2001, psychopathic behaviour patterns = damage to amygdala.

Raine et al. increased recidivism in people with smaller amygdala.

Evolution

Mazur 1983, increase in inter-male fighting around puberty because of testosterone.

Addiction/neurotransmission

Cocaine: increases dopamine activity and blocks reuptake.

Opiods e.g. heroin: reduces GABA, overactivity of dopamine.

Hormones

Edwards 1968, injected neonatal female rodent with testosterone increased aggression.

Ozaki et al. 1996, testosterone lowers serotonin levels = agg

Hawke 1951, castrated sex offenders = loss of sex drive and agg.

Mazur and Booth 1998, testosterone levels change across lifespan e.g. lessens during marriage. Supports basal model (increase = agg)

Twin studies

Gottesman and Shields 1966, 42% MZ also schizophrenic, 9% DZ. Genetic element schizophrenia.

Coccaro et al. 1997, high con rate for measures e.g. indirect assault.

Adoption studies

Cadoret and Stewart 1991, boys increased attention deficit and agg if bio parent convicted of a crime. Also found the same if there are psychiatric problems in adoptive family.