194 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”The enzyme monoamine oxidase A (MAO-A), which breaks down
the monoamine neurotransmitters norepinephrine, serotonin, and
dopamine, has been negatively correlated with aggressive behavior
across species. In healthy men, the lower the MAO-A activity in cortical
and subcortical brain regions, the higher the trait aggression and pre-
dicted antisocial behavior.^34 In a 30-year longitudinal study, people with
the low-activity variant of MAO-A genotype are more likely to develop
offending conduct and hostility.^35
Pheromones, the volatile chemical signals between animals per-
ceived through a special organ in the nose (vomero-nasal organ), acti-
vate the subcortical center amygdala. In lower animals they are potent
stimulants of instinctive responses (especially the emotion of lust) at a
subconscious level. These socially relevant chemical signals are found in
discharges like tears, sweat, vaginal secretions, and urine.
The effect of neurotransmitters on emotion and mood is depicted
in Figure 9.4.
9.8 Appraisal Precedes Emotion
Early in the twentieth century, Cannon and Bard showed that
animals could be induced to express anger and defense reactions
Fig. 9.4. Diagram showing very rough correlation of neurotransmitters with emo-
tion and mood. The proper function of the transmitters is essential for a balanced
emotional life.