Course Handout - Resource Allocation Theory

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First published online 16:12 GMT 18th March 2003, Copyright Derek J. Smith (Chartered Engineer). This version [HT.1 - transfer of copyright] dated 12:00 13th January 2010


Norman and Bobrow (1975)

This is the paper usually cited as the origin of "Resource Allocation Theory". It was written by Donald A. Norman, of Northwestern University, and Daniel G. Bobrow, of the Xerox Palo Alto Research Centre. The basic propositions of this paper are as follows .....

1.       That when considering biological information processing systems there is a lot to be learned from what goes on in man-made information systems.

2.       That cognitive functioning involves a whole group of independent processes, constantly exchanging information. These may be referred to as "programs".

  1. When programs are "executed" [that is to say, put into operation in some way], they require input data and have to compete for "resources". Norman and Bobrow define resources as "such things as processing effort [presumably brain tissue of some sort], the various forms of memory capacity [presumably brain tissue of some sort], and communication channels [presumably brain tissue of some sort]" (p45).

ASIDE: There are some very basic problems touched on here, because it is actually far from established which brain structures do the processing, which do the memorising, and which do the communicating.

  1. It is implicit in (1) to (3) that there is also some form "supervisory system" capable of directing the overall process. However, this topic was not added to the theory until five years later - see next section.

Given these basic propositions, it follows that there are two ways a given process can run into trouble. The first of these is if the volume of information currently available exceeds the system's powers to cope. This is known as "data-limited" processing. The other form of limitation is where the data are not excessive, but the resources required to process it are. This is known as "resource-limited" processing.

Some clever theory is then provided to explain how different types of task will perform. The general rule is as follows:

"Most tasks will be resource-limited up to the point where all the processing that can be done has been done, and data-limited from there on" (p46).

The standard shape of this relationship is known as the "performance-resource function", and will normally have an RMIN, the minimum amount of resources required to do the task, and an RDL, the level of resources beyond which performance becomes data-limited. The thrust of this argument is summarised diagrammatically, and the shape of the resulting curve shown, in Figure 1.


Figure 1 - The Idealised Performance-Resource Function: Here is a plot of performance against resources for an idealised cognitive task. As we increase the available resources from zero (a state of sleep, perhaps), nothing happens at all to start with. Once we reach RMIN (Point A), performance jumps suddenly to a base rate (Point B). It then increases linearly with increasing resources until it reaches Point C, where it might level off again, waiting another minimum amount of resources (Point D). When Point D is reached, performance starts to increase again, initially quickly, but tailing off until at Point E no further improvement is possible because the process has reached the point where data-limitation takes over. Up to Point E, the process has been resource-limited, but from Point E to Point F it is data-limited, that is to say, it is now data, not resources, which limits performance. Finally, resources cannot exceed Point F, because they are themselves at an absolute limit. Different real-life processes consume resources at different rates. In fact, "most processes have both data-limited and resource-limited regions" (p49).

[The performance-resource function]

Enhanced from a black-and-white original in Norman and Bobrow (1975; Figure 1). Red annotation ours. This version Copyright 2003, Derek J. Smith.


Norman and Shallice (1980/1986)

Norman and Bobrow (1975) made no theoretical assertion as to what mechanism(s) decided what resources were needed to complete a task. The term "supervisory system" came along slightly later, when the concept of limited resources was incorporated into attention theory by Norman and Shallice (1980/1986) as a "supervisory attentional system". As such, this concept is effectively synonymous with the concept of "central executive" as used within Baddeley's Working Memory Theory.


Shallice (1988)

Shallice (1988) summarises the role of the supervisory system as follows:

"..... the Supervisory System [has] access to a representation of the environment and of the organism's intentions and cognitive capacities. It is held to operate not by directly controlling behaviour, but by modulating the lower level [resources] by activating or inhibiting particular schemata. It would be involved in the genesis of willed actions and required in situations where the routine selection of actions was unsatisfactory - for instance, in dealing with novelty, in decision making, in overcoming temptation, or in dealing with danger." (Shallice, 1988, p335.)

It therefore follows that the supervisory system concept is central (a) to human problem solving, and (b) to the deterioration of same following brain injury


Clinical Implications

Two papers are typical of how Resource Allocation Theory can be used in a clinical setting, namely Selinger, Walker, Prescott, and Davis (1993) (which interprets the problem solving performance of CVA patients from this theory's point of view [read all about it]) and Van der Linden, Coyette, and Seron (1992) (which focuses on the topic of central executive function and includes details of a research paradigm claiming to factor apart processing and storage functions [read all about it]).



Norman, D.A. and Bobrow, D.G. (1975). On data-limited and resource limited processes. Cognitive Psychology, 7:44-64.

Norman, D.A. and Shallice, T. (1980/1986). Attention to action: Willed and automatic control of behaviour. Centre for Human Information Processing (Technical Report #99). Reprinted in revised form in Davidson, R.J., Schwartz, G.E., and Shapiro, D. (Eds.) (1986), Consciousness and Self-Regulation (Volume 4), New York: Plenum.

Shallice, T. (1988). From Neuropsychology to Mental Structure. Cambridge: Cambridge University Press.