Some still assume that emotion is peripheral, but the time has come to recognize that emotion is central.
The claim that emotion is peripheral can be taken both literally and figuratively. From a literal standpoint, experts have argued about which physiology is necessary for emotional experience since the birth of experimental psychology in the Gilded Age. On the one hand, in his seminal essay "What is an emotion?" William James counterintuitively argued that when we encounter a bear, peripheral (i.e., below the neck) physiological changes occur (e.g., the stomach clenches, heart pounds, and skin sweats) which then generate an experience of emotion (e.g., fear). By implication, peripheral responses must occur before the feeling of fear.
On the other hand, his Harvard colleague Walter Cannon countered that brain activity causes both emotional experience and peripheral responses. Cannon based his argument on research (e.g., in which emotional responses could be evoked by stimulating the brains of cats, who continued to show those emotional responses after spinal cord lesions), as well as on physiological logic (i.e., peripheral responses were too slow, insensitive, and undifferentiated to drive emotional experience). Thus, although James was a creative thinker and persuasive writer, he reasoned from the armchair, whereas the stolid and understated Cannon (who also innovated influential concepts such as "homeostasis" and "fight or flight") brought data to bear on the debate.
I seem to keep revisiting this century-old academic scuffle. That's because peripheralist assumptions still form the backbone of many modern emotion theories (e.g., in the form of peripheral somatic signals, or embodiment, or indeed any sensory process purported to mediate emotion). Of course, peripheral responses can modulate emotion—but they are simply not fast or specific enough to mediate the kinds of rapid emotional responses that ensured our ancestors' survival. Emotion also undoubtedly generates peripheral responses, but without information about which came first, correlated action does not imply causal direction. To be fair to the peripheral view, scientists presently lack a quantitative computational model of exactly how the brain generates emotion, and the neural mechanisms are still being worked out. But as the next few years of brain stimulation, lesion, and imaging evidence accumulates, I am betting that the central account of emotion will prevail.
From a figurative standpoint, the problematic assumptions of emotional peripheralism run deeper. An even older debate focuses on emotion's function rather than structure. Specifically, is emotion peripheral or central to mental function? A peripheralist viewpoint might posit that emotion does not influence or even disrupts mental function. While the historical roots of such an assumption may reach back as far as Zoroastrian dualism, Rene Descartes typically gets the blame for importing dualism from the church to science. Descartes split the mind and passions by placing the mind with the spirit but the passions with the body (where they took the form of "animal spirits" purported to move the pineal gland). According to Cartesian mind-body dualism, the mind could thus operate independently from disruptions of excessive passions.
In contrast to this peripheralist vision, a distinct depiction of the centrality of emotion to mental function comes not from the West but rather from the East. The Tibetan Buddhist "Wheel of Life," represents passionate attachments as animals that occupy the hub of a spinning wheel, driving thought and behavior. In both schemes, excessive passions can divert thought and action, but in Descartes' scheme, emotion disrupts the mind from the periphery, whereas in the Buddhist scheme emotion drives the mind from the center. If emotion is central to mental function, then our inherited scientific map of the mind is inside-out.
Indeed, the absence of emotion pervades modern scientific models of the mind. In the most popular mental metaphors of social science, mind as reflex (from behaviorism) explicitly omits emotion, and mind as computer (from cognitivism) all but ignores it. Even when emotion appears in later theories, it is usually as an afterthought—an epiphenomenal reaction to some event that has already passed. But over the past decade, the rising field of affective science has revealed that emotions can precede and motivate thought and behavior.
Emerging physiological, behavioral, and neuroimaging evidence suggests that emotions are proactive as well as reactive. Emotional signals from the brain now yield predictions about choice and mental health symptoms, and may soon guide scientists to specific circuits that confer more precise control over thought and behavior. Thus, the price of continuing to ignore emotion's centrality to mental function could be substantial. By assuming the mind is like a bundle of reflexes, a computer program, or even a self-interested rational actor, we may miss out on significant opportunities to predict and control behavior—both in individuals and groups.
Literally and figuratively, we should stop relegating emotion to the periphery, and move emotion to the center—where it belongs.