2 Human cognition and error

Baddeley and Hitch (1974) put forward a more complex model of STM, the working memory model (Figure 2.2). They suggested that rather than several linear stores, memory is controlled by a central executive (CE), which is the attention element of the model. The model further includes the visuo-spatial sketchpad (VSS), which deals with all visual input (the inner eye), and the phonological loop (PL), which deals with all auditory input (the inner ear). Baddeley and Hitch proposed that we cannot utilise two sets of information using the same modality, for example read a book and watch TV or pay attention to a conversation while listening to music with lyrics. In 2000, they proposed the addition of a further element to the working memory model, the episodic buffer, in which information from separate conscious memory channels (such as VSS and PL) are integrated into single memory chunks and used as the buffering mechanism between working memory and LTM (Baddeley 2000). The buffer can access the LTM when necessary, to enhance the STM by including episodes stored in the LTM.

Figure 2.2 Working memory model.

The Baddeley and Hitch model has resonance within the emergency setting and the operating theatre. It suggests that by attending to too many similar stimuli, we may reduce our ability to consciously attend to important issues, and can easily miss a crucial piece of information.

Automatic Cognition

Some types of thinking appear to be fast and effortless and occur in the subconscious. These include well-practised procedures or behaviours that rely on pattern recognition. Automatic cognition is often mistaken for the capacity for multitasking: however, what appears to be multitasking is actually switching rapidly from one task to another. In undertaking a familiar task, we must be aware of the fallibility produced from our tendency to ‘let our minds wander’: to focus on what interests us but not specifically on, perhaps, the mundane task that we are undertaking.

It is LTM that requires and uses pattern recognition. However, it is important to realise that pattern recognition can also lead to an incorrect conclusion. What happens in reality is interplay between the short-term conscious working memory and the LTM store. More often than not, knowledge from the LTM about previous life events and learning can be recalled, and usually that recall is accurate. However, sometimes these retrievals are inaccurate and hence pattern recognition can lead to an incorrect conclusion. As a simple example, a personalised car number plate, ‘P 5 YCH’, may appear to spell PSYCH. On closer inspection it is clear that our pattern recognition has failed, as the pattern of the number 5 is close enough to the letter S to trick us into thinking it says PSYCH. In a clinical example, a patient with shortness of breath might be thought on initial impression to have asthma, when a fuller history and examination would have revealed diabetic ketoacidosis.

There are three levels of cognition control (Table 2.1). The first, which is the most basic and slow, is the knowledge-based level. In this we require slow, conscious attention requiring both visual and audible input to guide our performance. This type of control is flexible in that it will respond to instructions from others but it does require significant concentration. Needless to say, as we have all experienced, the individual can be easily distracted and thus error prone. Knowledge-based cognition is utilised in a number of situations. These include learning a new skill, suffering from work overload and, specifically, where there is a lack of rules or procedures. One can also become error prone in situations of fatigue and high stress. Under normal circumstances, however, this level of cognition is used for novel or new problems.

Table 2.1 ‘Skill rules knowledge’ framework of cognitive behaviour control

(Rasmussen 1983; adapted from Reason 2008)

At the higher level of cognitive function is the skill-based, automatic level and this is where skill and knowledge have been acquired to enable routine performance. In this instance, we have packaged a sequence of events, for example, rapid sequence induction in anaesthetics or, for foundation year doctors, assembling the information and skill for IV cannulation. As one becomes expert, these skills become automatic and, in some instances, become difficult to teach to others without consciously disaggregating their steps.

Activity Box

Consider, for example, an apparently simple activity that you take for granted – like approaching a sliproad on a motorway. Write down the elements of that process in your notebook.

Your list might have included:

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