Emotions can be regarded as the manifestations of a system that realises multiple concerns and operates in an uncertain environment. Taking the concern realisation function as a starting point, it is argued that the major phenomena of emotion follow from considerations of what properties a subsystem implementing that function should have. The major phenomena are: the existence of the feelings of pleasure and pain, the importance of cognitive or appraisal variables, the presence of innate, pre-programmed behaviours as well as of complex constructed plans for achieving emotion goals, and the occurrence of behavioural interruption, disturbance and impulse-like priority of emotional goals. The system properties underlying these phenomena are facilities for relevance detection of events with regard to the multiple concerns, availability of relevance signals that can be recognised by the action system, and facilities for control precedence, or flexible goal priority ordering and shift.

A computer program, ACRES, is described that is built upon the specifications provided by this emotion theory. It operates in an operator-machine interaction involving the task of executing a knowledge manipulation task (the knowledge domain happens to be about emotions). ACRES responds emotionally when one of his concerns (e.g. errorless input, being kept busy, receiving varied input, not being killed) is touched upon. Responses are social signals, shifts in resource allocations to the operator, interruption of current task-directed processing, and refusal to accept instructions. His flow of behaviour shows much of the preference-based predictability, response interference, goalshifts, and social signalling of human and animal emotional behaviour.