This is the last of nine parts.
1. Introduction
2. The cognitive processing element.
3. Ways of meeting the cognitive needs
4. Sequencers and the contextual overview in working storage.
5. Working storage : updating, and capacity.
6. Choosing how to meet the cognitive needs, and the implications for mental workload.
7. Learning and modes of processing.
8. Knowledge structures

The focus in this paper has been on accounting for the organisation of behaviour. The claim is that complex behaviour emerges from the use of structures built up from the cognitive processing element, as a function of the external and internal environment (context) at a particular moment. This context is inferred by previous behaviour, and then influences the choices about what cognitive task to do next, and how to do it, so flexible sequences of behaviour adapted to details of the circumstances are generated.

Traditionally, in simulation of human cognitive processes, it has been considered a weakness if a representation has a large number of degrees of freedom, as they make it difficult to test whether a simulation does match some particular behavioural data. However, in a complexity theory, degrees of freedom are seen as a strength, as they mean that a large number of different behaviours can emerge from a simple substrate. This could also have an advantage in accounting for why the nature and probability of human behaviour are so difficult to predict. Attempting to predict human behaviour is like weather forecasting : it is not possible to be right, but it is possible to be useful.

The key cognitive aspects of this account are:
* behaviour is organised in terms of cognitive needs and associated working storage, which are parts of cognitive processing elements,
* behaviour is active and need oriented, rather than occurring only in reaction to environmental events,
* the cognitive processing elements are built up into structures which carry out processing, and decide what best to do next and how to do it,
* the cognitive processing builds up an overview of the situation, which is structured by the cognitive needs, and acts as the context for the choice of later behaviour,
* in situations in which there is no (not yet a) context, behaviour follows a sequence of stages. This serial behaviour emerges from the contextual mechanism in particular situations, rather than being formally defined in advance,
* the choice of how best to meet a cognitive need involves meta-knowledge about the possible behaviours.
* this meta-knowledge choice is also involved in the control of mental workload and learning.

This paper described how the proposed cognitive mechanism arose originally from an analysis of actual behaviour in an industrial process operation task. The data on real performance suggest that several additional mechanisms are needed to account for human complex behaviour in a wider range of cognitive tasks. These mechanisms are needed to cover such points as :
* Working storage needs to be able to represent not only single independent variables, but also:
i. relations between variables,
ii. multidimensional constructs.
* There may be two types of working storage:
i. the overview, which is built up by processing, and then is available as a reference context for later processing,
ii. the temporary storage of items needed during a particular part of processing, which is not retained for later reference.
* The active search for the information needed, which is organised by the 'sequencers', may be overridden by:
i. a highly salient event in the environment,
ii. some aspect of the environment which is relevant to a cognitive need other than the one currently being thought about.
* Processing can return to a previous point in thinking, after an interrupt.

The final Sections explored extensions to this processing element, in particular two types of knowledge :
* meta-knowledge about proposed working methods, which is used in the choice of how to do a task, and is therefore a focal mechanism in the control of mental workload and of learning,
* knowledge which is referred to by processing. In dynamic tasks this can involve a very complex network of types, and levels of detail or immediateness of relevance, of knowledge.

It may not be possible to test or prove the validity of this 'cognitive element structures' approach by the conventional method of generating testable hypotheses. However, this approach works as an account of complex behaviour, as far as can be tested using pencil-and-paper simulation. And it has the strengths of parsimony, internal consistency, and the ability to provide an account of aspects of behaviour which it was not originally devised for (Section 6 and Section 7). The approach could be tested indirectly, as it makes testable suggestions about what would be effective designs for supporting human behaviour in complex dynamic tasks (see e.g. Bainbridge, 1983, 1991, 1993b, 1993c).

This paper has suggested that this approach to behaviour modelling is an example of a complexity theory, as several features of complex behaviour are emergent properties of the activity of simple elements, rather than being explicit in the underlying representation from which the behaviour is generated. This complexity appears in the 'sequencers', in the 'routines', and between the levels of behaviour organisation.
* In tasks in which it is not possible to build up a contextual overview, or an overview has not yet been built up, behaviour may follow a standard sequence. This emerges from the operation of the contextual mechanism in the 'sequencers', in particular circumstances (Section 4, part 4.5).
* 'Routines' may be carried out as serial behaviour, but have an underlying parallel/ simultaneous representation (Section 3, part 3.2.2).
* As a cognitive need is met by meeting other cognitive needs, overt behaviour has a hierarchical nature. However, the different cognitive needs are not necessarily stored in a fixed hierarchy of levels (Section 6, part 6.2).

The mechanism proposed in this paper has powerful potential for understanding several crucial aspects of complex behaviour, but not all of them ! It is not at all possible to claim that this is complete as an account of cognitive processes. It does not, for example, explain :
* perceptual and motor skills such as recognition-primed decisions,
* some aspects of inference processes,
* multitasking and planning.
* the elements which would be needed as the basis for building up knowledge structures.
* how learning occurs.
It will certainly be very interesting to see how much these processes could be accounted for by extensions to the mechanisms proposed in this paper.

©1997 Lisanne Bainbridge