programme is inappropriate. The person who put on his gardening clothes in-
stead of getting the car out exemplifies the way in which strong but unplanned
actions can occur in the absence of attentional control.
Schema Theory A more detailed theory was proposed by Norman (1981) and
by Sellen and Norman (1992). According to them, actions are determined by
hierarchically organised schemas or organised plans. The highest-level schema
represents the overall intention or goal (e.g. buying a present), and the lower-
level schemas correspond to the actions involved in accomplishing that inten-
tion (e.g. taking money out of the bank; taking the train to the nearest shopping
centre). A schema determines action when its level of activation is sufficiently
high and when the appropriate triggering conditions exist (e.g. getting into the
train when it stops at the station). The activation level of schemas is determined
by current intentions and by the immediate environmental situation.
According to this schema model, action slips occur for various reasons:
.Errors in the formation of an intention.
.Faulty activation of a schema, leading to activation of the wrong schema
or to loss of activation in the correct schema..Faulty triggering of active schemas, leading to action being determined
by the wrong schema.
Many of the action slips recorded by Reason (1979) can be related to this
theoretical framework. For example, discrimination failures can lead to errors
in the formation of an intention, and storage failures for intentions can produce
faulty triggering of active schemas.
Evaluation One of the positive characteristics of recent theories is the notion
that errors or action slips should not be regarded as special events produced by
their own mechanisms; rather, they emerge from the interplay of conscious and
automatic control, and are thus ‘‘the normal by-products of the design of the
human action system’’ (Sellen & Norman, 1992, p. 318). On the negative side,
the notion that behaviour is determined by the automatic or conscious mode of
control is rather simplistic. As we saw earlier in the chapter, there are consid-
erable doubts about the notion of automatic processing, and it is improbable
that there is a unitary attentional system. More needs to be discovered about
the factors determining which mode of control will dominate. It is correctly
predicted by contemporary theory that action slips should occur most fre-
quently with highly practised activities, because it is under such circumstances
that the automatic mode of control has the greatest probability of being used.
However, the incidence of action slips is undoubtedly much greater with
actions that are perceived to be of minor importance than those regarded as
very important. For example, many circus performers carry out well-practised
actions, but the danger element ensures that they make minimal use of the
automatic mode of control. It is not clear that recent theories are equipped to
explain such phenomena.
Behavioural Efficiency
It might be argued that people would function more efficiently if they placed
less reliance on relatively automatic processes and more on the central pro-
392 Michael W. Eysenck and Mark T. Keane