196 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”Both have heightened sympathetic activities, yet one is fleeing for its
life and the other lusting for a meal. The motivations are diametrically
opposite, yet their outward emotional expressions are for the most part
similar. For the zebra, in particular, the direction of flight is a matter of
life or death, and has to be decided instantaneously. Thus, emotion alone
without a clear-cut goal is biologically counterproductive.
It is hard to pinpoint any particular brain structure as the site of
appraisal. The good-versus-bad valuation is likely the outcome of inte-
grative function of the cerebral cortex and the multiple subcortical
emotional centers, most likely involving the hippocampus for the partic-
ipation of memory and learning. It can also be genetically programmed,
such as fear of snakes in many animal species or the fear of flying preda-
tors in ducklings (see Chapter 7, Fig. 7.13). The task may be carried out
at the fully conscious, minimally conscious, or subconscious level. When
valuation turns subconscious, the behavior becomes a habit or phobia.
For an unexpected stimulus, the default instinctive appraisal seems to
be that of aversion, as happens when a crawling insect suddenly appears
on your back.
9.9 An Updated Theory of Emotion
Figure 9.6 summarizes a reasonable mechanism of emotion. Emotion
in a broad sense can be divided into two components: (1) A periph-
eral component (outbursts) consisting of autonomic sympathetic
output from the hypothalamus. The resulting bodily responses give
rise to the observable outward manifestations and the inner visceral
sensations (interoception). (2) A central component consisting of the
cerebral cortex and the emotional centers. When an external stimulus
(exteroception) arrives at the neocortex on a conscious level,^ the mes-
sage is passed on to this central component for appraisal. If the value
is either good or bad, it is conveyed to the hypothalamus to trigger a
sympathetic discharge. If the emotional expression is consciously or
unconsciously suppressed, it may elicit only a subtle mood change