Experiment Module: Neuropsychologists Show How Emotions Affect Cognition and Decisionmaking.
When facing situations where their survival is at stake, all living beings have a repertoire of behaviours among which they must choose. Human beings offer the best example of this rule. Among all the animals, humans are the ones best able to perceive fine details of changing situations in their environment and to think of numerous different responses to them. In the Western philosophical tradition, our decision-making processes have been associated chiefly with our ability to think and to reason correctly about the various alternative courses of action open to us. However, the results of neurological and psychological studies over the past fifteen years have forced us to revise this perspective. These studies invite us to revisit our understanding of decision-making mechanisms and make room for an unexpected factor: l'émotion.
Deep in each temporal lobe of the human brain
lies a small structure called the amygdala. The human amygdala is about the size
and shape of an almond (hence its name, which means “almond” in Latin). Research
has shown that in animals, the basic function of the amygdala is to assign emotional
meanings to the sensory stimuli that it receives from the outside world. When
the amygdala receives one or more such stimuli, it makes a quick assessment and
presents the brain with a kind of “report” about what the organism should expect
from them. The amygdala classifies the content of each stimulus either as something
promising and desirable that the organism should approach, or as something dangerous
that it should flee or avoid. To make this quick assessment, the amygdala uses
a fairly rigid set of information that is innately pre-programmed, or “engrammed”,
in the circuits of the brain. The amygdala can also draw on the information acquired
bit by bit throughout the individual’s lifetime, the traces of which are stored
in the brain as conscious and unconscious memories.
But the amygdala does more than just produce reports. It also triggers a series of responses involving many other neural structures that are connected to it. First come the behavioural responses: movements of approach or avoidance, as well as gestures and sounds expressing the person’s emotional state. Next come the reactions specific to the autonomic nervous system: changes in arterial blood pressure and heart rate. The endocrine system also reacts: it may secrete adrenalin to mobilize the organism, or other hormones, such as testosterone, which stimulates sexual behaviour. Lastly, the amygdala triggers changes in the overall state of the nervous system, including emotional reactions such as joy or sadness. The stronger the emotions involved (a sudden rush of anger, for example), the more pronounced and visible these adaptive reactions will be. But they also affect our behaviour throughout the day on a smaller scale, so discreetly that they go unnoticed.
When the amygdala triggers all these physical changes, they are in turn perceived by the brain, through the body’s neural pathways and hormonal circuit. Antonio Damasio, a professor of neurology at the University of Iowa, has shown that this feedback of information from the periphery to the centre is very important for understanding the mechanism of human emotions and the role that they play in decision-making. As Damasio puts it, the brain continuously monitors the ever-changing landscape of the body’s organs and systems. Now let us look at the role of the brain’s frontal lobes. The frontal lobes account for just about one-third of the total mass of the human brain, and a far smaller proportion in other animals (for example, only 3% in cats). What role do the frontal lobes play in the process just described, and in the way that people plan their actions? A number of answers to this question have been obtained through studies of frontal lobe lesions and their effects on human behaviour. One of the most thoroughly examined cases has been that of the patient known as Elliot, reported by Damasio and Eslinger (1985), Elliot had undergone an operation to remove a benign tumour from the central area of his prefrontal lobe. Though technically successful, this operation changed his life dramatically. Until then, Elliott had been a successful businessman. After the operation, his work performance declined so seriously that he lost his job. Subsequently, he made a series of unfortunate financial and professional decisions that caused him economic problems. His private life was no better. He divorced his first wife, remarried, and then divorced his second wife as well. To make things worse, the government refused to pay him any disability benefits, because he could not prove that his brain was not working normally. The standard neuropsychological tests did not reveal any significant pathology. He scored average or above average on all the tests. His perceptual, learning, language and mathematical abilities appeared to be intact, as did his memory. But the problems that he was experiencing clearly showed that something was wrong. That something was his ability to solve the problems of everyday life. Neurophysiologically, this ability depends on cooperation between the brain structures discussed above, the amygdala and the frontal lobes. Damasio has proposed an original theory of the mechanisms by which these structures interact.
According to Damasio, to deal with the variety of choices available to
it, the prefrontal cortex develops very transient images of its alternative scenarios
for action. In addition to their information content, these images trigger, via
the amygdala, representations of suitable emotional responses to this content.
These representations include, among other things, the corresponding somatic reactions–the
“modification of the bodily landscape” referred to earlier. Domasio calls these
reactions “somatic markers” and hypothesizes that their function is to associate
a distinct positive or negative bodily response with every action image. These
markers would let the brain make choices very quickly, by eliminating certain
action scenarios right away and preselecting others just as rapidly. According
to Domasio, these mechanisms would be faster, more efficient, and more effective
than rational assessment processes. But these mechanisms would benefit the rational
processes by taking over a large part of their work and leaving them free to concentrate
on solving the kinds of problems at which they are best.
The key to Elliot’s case, according to Domasio’s
theory, is that his brain surgery interfered with one of these mechanisms. People
who suffer from insufficient communication between the frontal lobe and the amygdala
would have problems in making subtle emotional assessments of the content of possible
actions. For this reason, these people would be unable to make delicate, personal
decisions. Thus we see that emotions, far from interfering with the making of
rational decisions in everyday life, actually constitute the essential condition
for them. Neurobiology thus confirms Pascal’s famous saying: "The heart has
its reasons that the reason does not know.”
Damasio, Descartes' Error: Reason, Emotion and the Human Brain , (NY: Grosset/Putnam,