complex tasks such as driving at high speeds in variable weather conditions and road conditions. Yet,
research has shown that there is a limit to what humans can handle.
It is well documented that human error on the road causes minor injury to fatal accidents and even
damage. Treat et al (1977) calculated that human error is a major contributing factor in 90% of
accidents and was also the only factor in 57% of accidents.
This essay will consider two theories of psychological research on human memory. Attention and
perception that can be used to assist understanding of the cause of human error on the roads.
It will provide an overview of these two theories and the limitations in human information processing
that contributes to accidents. It will also consider human error and how the research mentioned can be
applied to minimise driver errors on the roads. It will conclude with a number of possibilities considered
to reduce human error.
Several studies noted that capacity of humans to process information is limited in capacity.
Green(1991)research confirms that the flow of information whilst undertaking everyday tasks as driving
is complex with the driver handling various information at the same time such as auditory and visual
input vehicles, pedestrians, road signs, weather conditions. There is a continuous demand on the
driver’s memory who is also handling other auditory information such as talking to other passengers,
listening to music, and recalling or recognising directions.
Information processing theory is used to explain the importance of attention. Several studies show that
accidents occur when the driver was focussed on something else. Several studies reveal that the driver
can carry put all of the above tasks if visual and auditory input is low. However, if there is an increase in
demand for attention when there is poor visibility or the driver is driving very fast, or driver is affected
by fatigue or alcohol then attentional capacity is reduced.
This limitation in capacity relates to bottleneck theories which suggests information enters the
awareness one at a time whilst the information capacity theories propose information is processed
through various channels, but each channel has a limited capacity. The driver does not have the capacity
for inputs; they can only pay attention to certain number of information.
Broadbent(1958),Treisman(1960) and Deutsch & Deutsch(1963) put forward the theories of selective
attention that remains influential, despite current theories focus on capacity theory, and the decay of
information explained by Baddeley & Hitch(1974).
Broadbent Filter Model theory is based on Atkinson and Shiffrin multi-store memory model (1968) that
explains memory processes and sequences stages; sensory, short-term and long term memory. The
research confirms that the driver processes two types of stimulus. According to Broadbent the input
comes through the filter and the other stimuli are held in a ‘bottleneck’ for processing later.
Baddeley & Hitch (1974) working memory not only has limited capacity but also information decays,
this gives limitation in regards to new information being held. There is some difficulty with Filter model
Theory of attention. Cherry (1953) ‘cocktail party effect’ experiment confirms the subject focuses
attention on interesting stimuli whilst ignoring other stimulus. Again, Treisman (1960) proposed that if
stimulus has meaning it can be processed, whilst Deutsch and Deutsch (1963) proposed that if stimulus
needs to be responded to it can be selected later.
The conclusion to be drawn from this, is that driver capacity to interact safely on the road is reduced
and the possibility of human error increases because of the demands placed on attention. With such
complex tasks as driving, information would not be retained or recalled, and as the capacity for inputs
are limited the driver can only pay attention to certain pieces of information, so information which
could be important could slip from memory. The issue remains of how to get drivers to focus their
attention fully on the road.
Human perception is another research area that can be applied to human error on the roads. Human
perception is based on context and expectations the bottom up and top down approach. Several studies
reveal that perceptual error jeopardise road safety. For example drivers often admit to not seeing visible
information such as pedestrians crossing the road. In addition drivers misinterpret information such as
speed or closeness to other vehicles. or drivers misread the speed or the closeness of other vehicles.
Mack & Rock (1992) researched visual perception of unexpected shapes whilst looking at it directly. This
phenomenon is called inattentional blindness or perceptual blindness. This phenomenon occurs when
subjects do not see visible objects in front of them. This can be for reasons such as overload of
information or their attention is focussed on something else that has meaning, or no internal reference to the visible object. Simons, Chabris (2004) experiment on perception resulted in showing how subjects did not see an incident happening in front of them. This experiment involved participants playing basketball game and missing an unexpected appearance of someone dressed up in a white gorilla suit walk onto the ball court during the game. Subjects did not recall seeing the white gorilla.
Scholl et al (2003) research also suggests that auditory input such as talking on mobile telephone can increase the opportunity of a subject failing to notice the unexpected and leading to increased human errors.
This research on perception has implications for road safety, as drivers often report they did not see the
pedestrian or car in front. The driver focus on what they expect to see ‘top down processing’ rather
than on the unexpected objects. This results in the likelihood of important and unexpected objects being
missed. Neisser (1976) suggests that is not either or for humans. Perception involves both top down and bottom up processing becoming a perceptual cycle.
Reason (1991) extensive research on human error defines error “as circumstances in which planned
action fail to achieve the desired outcome.” Examples of this are stepping on the brakes too late and
failing to stop at red traffic lights. Norman & Shallice(1986) and Reason(1991)theory could be used to explain human error in driving tasks and knowledge. Norman and Shallice propose two types of control ‘ controlled control’ and ‘automatic control’. Controlled control being within awareness, but conscious and limited and automatic control out of awareness, creates automacity in tasks already rehearsed over a long period of time. This become out of awareness and is performed without effort like driving.
Reason (1991) also suggests that there are 3 types of cognitive processes that cause errors.
- Skills based error or slips these consist of automatic action that was unconscious
- Rules based mistakes these consist of non-appliance of a heuristic to undertake a task
- Knowledge based conscious thought to solve a problem
Finally Reason (2000) Swiss Cheese Model of human error can assist in understanding how road accident
occurs. All slices of the cheese model have gaps which have to be aligned for an accident to occur. Thus
a combination of factors can cause human error. To reduce the chance of accident road experts could
use Reason model to identify the factors that contribute reducing unsafe acts such as talking on mobiles
whilst driving, visible multiple cues, signals, colour coding, speed limits and road examinations are some
of the examples observed to reduce road fatalities.
This essay has attempted to briefly explain the psychological research on memory that could be applied
to the road. It concludes that this research on attention and perception can help to understand the
cause of human errors on the road. However, memory research is still laboratory based, and opens to
criticism regarding ‘ecological validity’. In deed human error is inevitable and getting humans to adapt
their behaviour may prove challenging.
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