HAL: Dave, stop ... Stop, will you? Stop, Dave ... Will you stop, Dave ... Stop, Dave. I'm afraid ... I'm afraid ... I'm afraid, Dave ... Dave ... my mind is going ... I can feel it ... I can feel it ... My mind is going ... There is no question about it. I can feel it ... I can feel it ... I can feel it ... I'm a ... fraid ...

HAL's expression of fear and his impassioned pleas no doubt struck a responsive chord of feeling in many viewers, for here HAL gives us the impression that he is not a heartless machine but a being who has genuine emotions.

Emotion is not simply a luxurious extra in 2001. In film and theater, carefully controlled and expressed emotion has the ability to influence us and, subsequently, to affect whether we like a production and remember seeing it with pleasure. Surprisingly, in 2001, the machine expresses more emotion than the humans. Many viewers feel a greater loss when HAL "dies," than they do when Frank Poole floats away into space. Emotion is a powerful tool in the hands of artists like Kubrick and Clarke. But what about emotions in computers - -- for purposes other than entertainment?

Computers today don't emit plaintive cries when being disassembled, and most users wouldn't pay extra to get this feature. Instead, computers emit messages such as unexpected fatal error -60. They don't have emotions per se, although it is not unusual to hear someone yelling at a computer -- as if it might feel sorry and change its behavior. If you yell at a puppy, perhaps because it wet on the rug, the puppy senses your anger and usually learns to correct its behavior, even wagging its tail to indicate delight when you finally appear pleased. Computers, by contrast, neither recognize your anger nor feel good or bad because of it. They don't notice whether you're attentive, annoyed, or have fallen asleep in front of them; they continue to "wet on the rug," so to speak, regardless of whether or not you yell at them.

Are emotions a desirable property for computers to have? It's hard to imagine someday walking into a computer store and saying, "Give me the most emotional machine you've got." After all, isn't possessing the highest form of rationality one of the hallmarks of computers? Aren't Mr. Spock and Data the unemotional patron saints of computer scientists? Imagine how a computer with emotion might work -- perhaps it would have to feel interested before it would listen to what you have to tell it. On the face of it, emotions in computers sound absurd. After all, didn't emotion cause HAL to malfunction?

On the other hand, it would be tremendously worthwhile to have a computer that is congenial to interact with, flexible in its approach to doing what you want, makes snappy and intelligent decisions, and offers creative solutions to problems. It may surprise you to know that emotion plays a key role in all these qualities. In fact, emotion appears to be a necessary component of intelligent, friendly computers like HAL. The inability of today's computers to recognize, express, and have emotions severely limits their ability to act intelligently and interact naturally with us. But emotion without balance can also lead to disaster, as it does in 2001.

In the next few sections I discuss what we mean by emotion, what special emotional abilities HAL possesses, and some of the ways in which computers are becoming "affective." I then describe a paradoxical discovery -- the importance of emotions in computers -- look closely at HAL's disaster, and consider a dilemma regarding emotional machines.


What Is Emotion?

Emotion is a slippery word to define. Internal human states like fear and anger (what psychologists call affective states) seem obvious aspects of emotion. But what about interest, boredom, hope, frustration, and lust? The fact is that even emotion researchers don't agree on a definition of emotion, and many of them don't consider such feelings as love to be basic emotions. They also argue about whether there are any basic emotions, or whether, instead, there are only continuous states or just different kinds of thoughts that we label emotions. It may be a long time before researchers come up with a commonly accepted definition of emotion.

Fortunately, we don't need such a definition to understand this chapter; an intuitive notion of emotion will suffice. Nonetheless, the terminology can be confusing. Note that the word feeling doesn't always imply emotion; squeezing scrambled eggs between your fingers feels squishy, and is a tactile feeling, not an emotional one. On the other hand, we often use the words affect and emotion as, essentially, synonyms. In this chapter, we make notable exception to this practice when we use the forms to modify computing. In that case, because emotional computing tends to connote computers with an undesirable reduction in rationality, we prefer the term affective computing to denote computing that relates to, arises from, or deliberately influences emotions. Affective still means emotional, but may, perhaps usefully, be confused with effective.