On Emotion

Emotions have had many uses throughout human existence, and the details of these uses, or functions, have been the focus of a considerable amount of research in recent times. A functional definition of emotion is useful because it provides clear criteria for the detection of emotions, independent of the agent experiencing it.

De Sousa's [5] main idea as to the functions of emotion are in terms of salience, and the significance problem. The significance problem is that given access to a massive amount of information, knowing which information is relevant before accessing it. If an agent is experiencing a mood state they have experienced before, then they can use their previous ideas (inherited or learned) about what knowledge has previously been useful.

De Sousa lists two biological hypotheses (these are repeated verbatim here):

• New Biological Hypothesis 1[page 195]. The function of emotions is to fill gaps left by (mere wanting plus) ``pure reason'' in the determination of action and belief, by mimicking the encapsulation of perception: it is one of Nature's ways of dealing with the philosophers' frame problem.

• New Biological Hypothesis 2[page 196]. Emotions are a species of determinate patterns of salience among objects of attention, lines of inquiry, and inferential strategies.

De Sousa defines the ``philosopher's frame problem'' as distinct from the Artificial Intelligence community's traditional frame problem (see [11, page 207]. It is the problem of deciding how not to retrieve irrelevant information before it is retrieved.

Rolls' [3] ideas of the functions of emotion follow from his beliefs that emotions are states induced by most kinds of reinforcing stimuli. Rolls lists a number of functions for emotion, some of the more important are:

• Emotion facilitates the elicitation of autonomic responses which include heart rate increase and adrenaline release.
• Flexibility of behavioural responses via two stage learning. The idea is that we have many learnt and inbuilt responses for dealing with emotions, and mapping stimuli to emotions provides for more flexibility, quicker adaption, and simplicity.
• Emotion is motivating, in that agents will work towards achieving some emotional state (happiness) and work to prevent others (sadness, fear).
• Communication. It is known that there are a variety of facial responses in humans and perhaps monkeys which correspond to emotions. Also dogs tails wag when they're happy, and cat's tails lash when threatened, or angry. This function is very similar to Darwin's [6] ideas of emotional expression.

Parts of both of these theories can be interpreted in terms of speed of processing. De Sousa's idea of emotion controlling salience is critical; an agent might be deliberating over, say, whether to devour a suspect piece of food. A predator might appear, drawing the agent's attention from the food, and forcing it to act before its ready. Rolls' idea of autonomic response inducing (see also [2]) stresses the importance of emotion in eliciting speed of response.