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Associate professor of psychology, Georgetown University
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The neuroscientist Antonio Damasio describes a patient named Elliott who sustained a massive injury to his ventromedial prefrontal cortex following surgery to remove a tumor. Elliott’s considerable intelligence was unaffected by the surgery, including those components of intelligence that can be replicated in computers: long-term memory, vocabulary, and mathematical and spatial reasoning. Nevertheless, Elliott lost his ability to function. Why? Because, like other patients with injuries to this region, Elliott could no longer use his knowledge and intelligence. His brain damage destroyed his emotional capacities, rendering him unable to make decisions or take action.
Making a decision requires emotion—requires wanting one outcome more than another, and wanting is fundamentally emotional. The visceral pang we experience as “wanting” results from activity in subcortical brain circuits in the limbic system and basal ganglia, particularly the amygdala and nucleus accumbens, which are active in response to cues signaling that a stimulus may result in desirable or undesirable outcomes. Information from these structures is fed forward to the ventromedial prefrontal cortex, which is the final common pathway responsible for mediating among disparate choices and arriving at a decision.
When we opine that a particular choice is like “comparing apples and oranges,” we don’t mean it’s impossible to arrive at a decision. It’s not difficult for people to decide whether they’d prefer an apple or an orange, or beer or wine, or pizza or a burrito. We mean that there’s no rational, objective basis for making this decision, no numerical formula that stipulates a choice. So human decision makers rely on the vague and qualitative feeling of wanting one option more than the other, a feeling that represents the activities of our prefrontal cortex working in concert with subcortical emotional brain structures to compare the options. A patient like Elliott, in whom this capacity has been destroyed, is stymied in trying to make what should be a simple decision. Unable to generate an internal sense of wanting something, he struggles to decide what to eat for lunch, or when to schedule a doctor’s appointment, or which color pen to use to write the date in his calendar. He is, in this way, similar to people with profound depression who experience anhedonia. These patients spend days on end in bed because anhedonia robs them of the expectation that something will generate feelings of pleasure or enjoyment, so they do nothing. Again, their essential impairment is one of feeling.
We have nothing to fear from machines that think unless they can also feel. Thinking can, by itself, solve problems, but that’s not the same thing as making decisions. Neuroscience tells us that an entity unable to generate the experiences of wanting a desirable outcome or fearing an adverse one will remain impassive in the face of choices—about civil rights or government or anything else. Fundamentally anhedonic, it will remain forever bedbound rather than rise up. Neuroscientists are so far from understanding how subjective experience emerges in the brain, much less the subjective sense of emotion, that this sense will probably not be reproduced in a machine anytime soon.
If it is, we must tread carefully. In addition to feeling emotion, humans can understand others’ feelings and, more profoundly, care about what others are feeling. This sense of caring probably originated as part of the ancient neural architecture that keeps parents attending to their vulnerable young rather than abandoning or eating them. We share this sense with other mammals and with birds; it’s what separates the social dolphin from the solitary shark. Both creatures can feel, but only dolphins can feel for others. As a result, humans can expect very different treatment from sharks and dolphins. Although they’re fearsome predators, dolphins frequently protect vulnerable human swimmers, sometimes from sharks. Any attempts to create machines that can feel, and can therefore decide to take action, must include enabling them to care for others as well—must create mechanical dolphins rather than sharks—if humans are to have any hope of surviving among them.
