This is the second of nine sections.
1. Introduction

Figure 2.1 : Components of the cognitive processing element (Bainbridge, 1972, 1992)

2.1. The basic element

Figure 2.1 shows the components of the basic processing element and its links. (The element was previously called a 'module', but this was confusing as it does not distinguish the basic element from the structures it can be built up into.)

There are five main parts of an element, in two groups :

A. a need/ working storage pair :
1. a statement of a cognitive need. In previous papers this was called a cognitive 'goal', but the word goal causes problems. Another possible term would be cognitive 'function'.
2. the associated working storage, indicated by boxes. The left hand box (not shown in all Figures) represents the input parameters for the element, the context which determines what specifically is needed. The right hand box represents the result of the processing to meet the cognitive need.

B. three types of link between these pairs :
3. the link to the processing for meeting the cognitive need. This link is indicated by a stepped arrow (arrows may be stepped left or right in the Figures, for convenience of visual layout). (This link plays a special part in the choice and organisation of behaviour, which will be discussed in Section 6.)
4. the links between cognitive needs, by which they are built up into larger structures or 'routines', which meet other cognitive needs. These links are represented by dashed lines. (They are discussed further in Section 3.)
5. the cross references between different parts of working storage. These are represented by solid lines. (These cross references, and the nature of the context for behaviour, will be discussed further in Section 4, Section 5, and Section 6.)

As well as the elements and 'routines', other key aspects of the proposed cognitive processing mechanism, discussed later, are :
* the combination of conditional elements into 'sequencer' structures which retain an overview of the state of the task, and which determine the sequence of behaviour, what to do next. This is discussed more in Section 4.
* the meta-knowledge associated with 'routines', which is used in the choice of best working method, how to do something. This is discussed more in Section 6.

Superficially, this element might just look like an unnecessarily complicated if-then element. However, later sections of this paper will show the power of these properties of the element :
* the cognitive needs act as the focus for the organisation of behaviour (Section 3, Section 4, and Section 6.)
* the contents of working storage are built up by cognitive activities. The contents are not simply a representation of unprocessed input information, and the contents are structured by their relation to the cognitive needs (Section 3).
* the links between the working storage items build the working storage up into a contextual overview, which is cross-referenced by other cognitive processing, and is the basis for choosing what to do next and how to do it (Section 4, and Section 6).
* the goal/need and the means for meeting it are independent. The link between the two is a flexible and powerful decision point using meta-knowledge, which is involved in mental workload and learning (Section 6 and Section 7).

2.2. From the verbal protocol to the nature of the elements

But what was the origin of these proposed constituents ? This Section illustrates how the cognitive processing element originated from the protocol analysis. The first sub-section gives a protocol example. The second section shows how the processes underlying this protocol were inferred. The third section discusses why the processing has been represented by the element.

Figure 2.2.1 : A sample protocol fragment. (Bainbridge 1972, 1985)

Analysing the verbal protocol

In the furnace power allocation task (e.g. Bainbridge, 1974) the operators were asked to speak their thoughts out loud, and this verbal report was recorded and transcribed. Figure 2.2.1 shows a short section of protocol from an inexperienced subject. Five furnaces are involved, named A, B, C, D and E. Each furnace goes through a sequence of stages in the steel making process - charge, melt, half-melt, oxidise, reduce, tap, fettle - at its own rate, depending on its size and what type of steel it is making. The protocol fragment in Figure 2.2.1 shows the operator predicting when a furnace will change from one stage to another. This section of protocol has already been divided into distinct phrases, on the basis of natural language understanding. Figure 2.2.2 shows the same protocol, with each successive phrase written on a different line. An analyst has judged, on the basis of natural language understanding and knowledge of the task, which of the phrases are linked together. These links are shown by the connecting arrows.

Figure 2.2.2 : The protocol in Figure 2.2.1 divided into phrases, with cross references between them (Bainbridge 1974, 1985)

Identifying the underlying processing

To make a simulation of the thinking described in the protocol, it is necessary to identify the processes underlying the protocol. The phrases in Figure 2.2.2, for example, fall into two groups, which are differ considerably in detail, but are both concerned with predicting the time when a given furnace stage will end. So the analyst's aim is to find what common processes are carried out whenever the person predicted the end of a furnace stage, and to describe these processes in such a way that they could be used for any furnace or stage of steel making. The aim of the simulation was to represent the underlying thinking processes, not the details of the language in which they were expressed. It is of course a major assumption that the same processes underlie each time the operator predicts the end of a stage, rather than that the operator has a separate set of mental instructions for predicting the end of each stage on each furnace. In this case, however, the protocol evidence did not suggest that there were major differences, and also the prediction process had been described in the task instructions as a general strategy.

The protocol does not mention explicitly all the processing which must have been involved in any given piece of thinking. The underlying processing was therefore identified by combining two types of evidence : by drawing together information from all the occasions on which given processing was done (in the furnace operator study, a cognitive simulation was only suggested for processing which had been done at least twice), and by the analyst inferring any processing which must have been done in order for the operator to be able to say what he did, but which he had not explicitly mentioned. The process of combining these two types of evidence is illustrated in Figure 2.2.3.

Figure 2.2.3 : The processing underlying the protocol in Figure 2.2.2 (Bainbridge 1974, 1985).

It is obvious there is a large gap between what is in the protocol and what is given in Figure 2.2.3. This gap has been bridged by the analyst's assumptions. This process of simplification is done by human categorisation. What categories are used depends on the purpose of the analysis. The validity of the categorisation can be tested by using a number of judges. These aspects of protocol analysis are discussed in Bainbridge (1985, 1990).

Figure 2.2.4 : The processing in Figure 2.2.3 described in terms of the processing element (Bainbridge, 1974).

The processing element representation

Figure 2.2.3 shows a possible relatively conventional representation of the processing. Figure 2.2.4 shows the same processing represented by the proposed cognitive element. This representation was chosen after trying out many possible alternatives, because it makes several important aspects of the processing explicit, which are not shown in Figure 2.2.3.

The goal or function of the processing.
There are two aspects of cognitive behaviour which appeared in the protocols, and which it is useful to make explicit here.

a. The wording of a protocol often suggests that the person speaking knows what they want to do, and then (particularly in the case of an inexperienced operator) works out how to do it, e.g. phrases 2 or 11 in Figure 2.2.2. A representation is required which makes explicit the need met by the processing, rather than leaving it implicit in the final operation of the processing as in Figure 2.2.3. (The reasons for using a goal, or cognitive need, oriented account, are discussed further in Section 6.)

b. Also an operator may use several different ways of meeting a given cognitive need, at different times (see Section 6), so a representation is needed which makes it explicit that the goal of (or need met by) the processing and the means of meeting it are independent.

These two requirements of the representation are met by making the cognitive need the focus of the representation, and by indicating the goal-means link by a special stepped arrow.

The working storage.
Figure 2.2.3 does not make the cross references in working storage explicit. In trying to understand the protocol, it was found that working storage was a key underlying factor. It could for example be involved in the links between phrases indicated in Figure 2.2.2. (This will be discussed further in Section 3, Section 4 and Section 5). It was therefore useful to have a representation which made the working storage explicit. In these diagrams a box has been used, with arrows to represent cross references. In Figure 2.2.4 cross references within the group of phrases are shown in an abbreviated form, by arrows in the boxes. Figure 2.3.2 below is an example in which the cross references in working storage are shown in full.

The cognitive processing element thus originated as a form of notation which captured, or made explicit, various key aspects of the nature of the processing. Hopefully, why these are key aspects of processing will become clear in the rest of this paper.

TABLE 2 : Prairie Island Nuclear Power Station Incident, Time 1414
(Bainbridge, 1991, Table 1, adapted from Operator Decision/ Action Summary
in Pew et al, 1981, p.B-12).

Event, or operator comment	Underlying cognitive processes (inferred by analysis)
high radiation alarm on IR15 air ejector	INFORMATION AVAILABLE
	COGNITIVE INFERENCES BY OPERATORS :
occasional spiking produces false alarms, assume this is a false alarm	Interpretation
if not a false alarm, IR15 will alarm again	Expectation
monitor for further indications	Intention

2.3. A more complex example

A further example illustrates more detail about some basic aspects of how the element works. The behaviour in this example is a short section of the cognitive activities of a team of nuclear power station operators reacting to a high radiation alarm, as summarised in Table 2. The operators did not react to the alarm as an alarm, but used their knowledge of the process to infer what had happened. A simple generalised and goal-oriented account of the operators' activity could be :

infer state of process by
1. find possible causes of displayed information.
2. select one of these by
i. find which one has the highest frequency.
3. check interpretation by
i. find nature of distinguishing evidence
ii. look for/ wait for distinguishing evidence
iii. compare actual with expected.

In this representation, what the operators do is expressed in terms of their cognitive needs, which are met by carrying out more detailed cognitive processing, also described as cognitive needs. Level of detail is indicated by type of number.

Figure 2.3.1 : Element representation of the processing in Table 2 (Bainbridge, 1992). See also Figure 2.3.2 and Figure 3.1.

This sequence of instructions could be implemented in many ways. Figure 2.3.1 shows how they could be implemented using the processing element. Two main aspects of the links between elements will be introduced in this section : the transfer of control between parts of the processing, and the use of working storage.

Transfer of Control

Two types of transfer of control are represented, within and between the levels of organisation of the behaviour. Figure 2.3.1 shows three levels of detail, The highest level element could be called the 'originating cognitive need', and in some diagrams is indicated by a double lined box called a 'head' box. (The need for a special term will become clear later). Passing control from one level of detail down to another is shown by a stepped arrow. Within one level, the elements are linked by dotted lines. So two types of transfer of control are represented, within and between the levels of organisation of the behaviour.

a. Links between levels are represented by the stepped arrow, meaning 'the above is implemented by doing the following'. The stepped arrow also indicates a goal-means separation : the cognitive need is independent of the means by which it is met. This gives the possibility of great flexibility in behaviour, as discussed in Section 6.

To make Figure 2.3.1 simple, it does not show explicitly how each of the cognitive needs is met, there is not something at the end of every stepped arrow. For more on this, see Section 3 and Figure 3.1.

b. The arrows made of dashed lines represent transfer of control between cognitive needs within the same level. Items linked together by dashed arrows make up a 'routine' which meets a higher level cognitive need. In this example, the 'routine' is somewhat like a conventional programming routine, but this is misleading as these 'routines' have some different properties which are discussed in Section 3 (part 3.2.1)

Working Storage

Working storage ('working' storage in the sense that these items only need to be stored while the task is being done) is represented by the boxes associated with the cognitive needs. The left-hand box is for the input parameters, so that what the lower processing finds to meet the need is specific to the given circumstances. The right-hand box is for the results of carrying out the processing which meets the need (e.g. in the nuclear example, what is found as a result of looking for possible causes).

Figure 2.3.2 : Cross references in working storage (Bainbridge, 1992). Where this Figure does not show how the cognitive need is met, see Figure 3.1.

The cross references between items in working storage are not represented in Figure 2.3.1. Figure 2.3.2 does show these local cross references. The left hand box receives the inputs, which are either passed on from the inputs of previous cognitive needs or come from the result of meeting previous cognitive needs. The right hand box represents the result of meeting the cognitive need. This result may then be fed 'down' the levels of processing, for use in later cognitive processing. Or it may be fed 'up' the levels of processing, as a result which gives the result needed at a 'higher' level.

The boxes and cross reference arrows are not meant to imply actual storage or transfer of data from one place to another. It could be more appropriate to think of the arrows as type-token links referring to data stored elsewhere, and the box as a symbol for a point at which the results of processing could be available.

Evidence (see Section 4, part 4.4) suggests that the data found by a main 'routine', for the originating cognitive need, may be available for a longer period of time than just during the 'routine', and may be referred to by other 'routines'. This will be called continuing working storage, and may be represented by a double-lined 'head' box. The working storage items cross referenced within a 'routine' appear to be available for reference only during that 'routine', so this type of local storage is temporary. As cross references are only either within a 'routine', or to continuing working storage, this might suggest that a 'routine' is an independent processing module. This is discussed more in Section 8, part 8.2.1.

Other aspects of behaviour (see Section 4, part 4.3) suggest that the contents of working storage are available in parallel. It is possible to think of these boxes as a special type of blackboard, in which the contents and the format of this blackboard are inherently structured by being related to the cognitive needs and the links between them. And only the 'head' data is available to later processing (see Section 4, part 4.4).

The term working 'storage' is used in this paper, rather than working 'memory', because this working storage is not simply a memory for items which are replicas of the input information. Working storage here is a task-related temporary structure of data which has been transformed and interrelated as a result of task thinking to meet the cognitive needs. For example, the person does not necessarily remember the value of a process variable, but what this value implies for action, and what the action should be. They may not remember the specific times of events, but use these data about times as part of working out what will happen next, what this will imply for action, and what to do about it. So this working storage is a cognitive structure, and it may not be possible to infer what is in it simply from observing what information the person takes in and what actions they make. The cognitive processing elements make this use of working storage explicit (which is not usually done in descriptions of cognitive processing), because working storage is such an important mechanism, both in linking together local processing, as outlined in this Section, and in providing the context for the organisation of more complex behaviour, see Section 4, Section 5, and Section 6.

The rest of this paper will discuss in more detail the properties of the element outlined here, and its potential for accounting for complex behaviour.

Summary of main points in Section 2

* There are five parts to a processing element :
i. a statement of a cognitive need,
ii. associated working storage for the result of carrying out the cognitive processing which meets this need,
iii. links to processing for meeting the cognitive need,
iv. links between cognitive needs, building them into larger structures,
v. cross references between different parts of working storage.

* The method ('routine') for meeting a cognitive need is itself made of linked cognitive needs.

* Cross references between working storage items within a 'routine' also link the 'routine' together.

* The cognitive needs and the cross references structure the working storage. The contents of working storage are available in parallel, it acts as a kind of structured blackboard.

* Working storage contains the result of the thinking which meets a cognitive need, so contains transformed data, not simply a representation of the outside world.

* The result found by a main 'routine' is maintained in working storage for a longer time, and is available for reference by other processing.

©1997 Lisanne Bainbridge