HAL, of course, doesn't have to rely on text-only communication with Frank and Dave. Not only can he hear and see them and speak to them, he has at least two other essential abilities: (1) HAL can express affect (as we saw above); and (2) he can recognize affect.

Consider the following snippet of dialogue, which occurs after HAL refuses to let Dave back on the ship and Dave manages to reenter and start to disassemble HAL.

HAL: Just what do you think you're doing, Dave? Dave? ... Look Dave, I can see you're really upset about this. I honestly think you ought to sit down calmly, take a stress pill, and think things over.

Here we see HAL's ability to recognize emotion in Dave, as well as his relative inability to recommend an intelligent course of action based on this recognition; that is, his lack of emotional intelligence. (HAL's recipe for stress reduction sounds eerily like that used in Huxley's Brave New World.) I'll say more about emotional intelligence below; but first let's look at how HAL recognizes emotion. In the novel 2001, Clarke tells us that HAL analyzes Dave's voice harmonics. We also might expect him to be able to interpret Dave's facial expression, as hearing and seeing are the only two perceptual abilities we know HAL possesses. We never hear that he has smell, taste, touch, or other physiological sensors.

However, close scrutiny of Dave indicates that his face is not very expressive; he rarely deviates from the stereotypical appearance of the calm, cool, scientist. His voice too is usually well controlled and only becomes firm when he orders HAL to open the door. Dave displays his strongest emotions when HAL refuses to obey. This occurs right after HAL has killed Frank and everyone else on the ship. Dave, whose blood should be boiling by this time, gives only one subtle visual cue to how he feels: he straightens his lip in a barely detectable expression that is most likely an artifact of his attempt to suppress much stronger feelings that would be inappropriate to his cool scientific character. Earlier, while in the pod with Frank, Dave also shows subtle emotion - a slight lowering of his head - to agree with Frank that disconnecting HAL may become their only choice.

Otherwise, Dave is relatively impassive. In fact, all the humans in 2001 have rather machinelike demeanors. HAL, in contrast, is relatively expressive.

Moreover, HAL is two leaps ahead of today's computers in his ability to recognize emotion. Today's computers are affect-impaired; they blather on and on, filling your view with pages of output, regardless of whether you show interest or boredom. Would an intelligent human keep talking nonstop, face-to-face, after you close your eyes and open your mouth in a yawn the size of a barn door? Of course not. Then how can computers become intelligent friendly companions if they are not given at least the ability to recognize such emotions as interest, distress, and pleasure, which - some researchers claim - we are all born with (see figure 13.1).

Here is a scenario of how a computer tutor of the future might use recognition of affect to, perhaps, help you learn to play the piano. As you show interest in the topic and make rapid progress, it might provide optional interesting side avenues to explore. If you become distressed, perhaps because you are being pushed too far too fast, it might slow down and give encouraging suggestions, or revisit fundamentals. It might have the dual goal of maximizing learning and bringing pleasure but not pursue the latter goal 100 percent of the time, as some distress appears to be necessary for learning to occur. To be successful, the tutor would need to at least recognize and express affect. Ideally, it would also combine emotional intelligence (such as how and when to use empathy and how to adjust its teaching based on the student's affect) with other forms of knowledge - such as the subject matter and the best way to teach it.