Page 50 - Handbook of Electronic Assistive Technology

Chapter 2 • Cognitive Impairment and EAT 37

Attention

The human attention system allows us to make sense of our environment. It is excellent
at filtering the information that comes through our senses to allow us to focus on the task
at hand. The attenuation model of selective attention posits that information that enters
the senses is preconsciously either attended to or attenuated (Treisman, 1964) depend-
ing on physical properties such as loudness. Attenuated information is processed if it has
a low enough activation threshold, which is subjective to the individual for each piece
of information. For example, the cocktail party effect means that people attend to their
own name spoken in a crowd at a party because that information has more salience to
the listener and therefore a lower activation threshold than the other background noises.
Thinking about this theory of attention, there are many potential ways in which attention
could be impaired. The senses could fail to pick up information, or too much information
could meet the activation threshold causing overload. Neurocognitive disorders are often
linked with sensitivity to loud noises and dislike of noisy or busy environments (Wilson,
2009; Stiegler and Davis, 2010). There could also be a mismatch between the amount of
processed information that enters the working memory and working memory capacity.
This may explain the difficulties with dual tasking (e.g., walking and talking) experienced
by those with neurological impairment (Evans et al., 2009; Springer et al., 2006). Walking
takes up a small amount of the attentional processes and that usually does not impact
upon the performance of another cognitive task that requires attention (e.g., understand-
ing verbal information from a person you are conversing with). However, if working mem-
ory capacity is reduced, then the amount of information that is processed might be too
great resulting in the patient failing to understand what the person is saying and/or walk-
ing with an uneven gait (Evans et al., 2009).
Clinicians working with people with attention difficulties may categorise patients
according to the type of senses for which they experience attention difficulties. For
example, people may have a deficit in attending to one side of their vision, or heightened
sensitivity to sound. People may also experience difficulties with sustaining attention,
being distracted easily by environmental stimuli not relevant to a goal they are trying to
achieve. Alternatively, people may struggle to switch attention from one task to another
when appropriate. Sohlberg and Mateer (1987) developed a clinical model of attention to
describe people’s difficulties and develop rehabilitation to help people overcome atten-
tion difficulties. They describe five levels of attention with increasing difficulty: focused,
sustained, selective, alternating and divided. Focused, sustained and selective attention
describe first discrete responding focused on environmental stimuli, the ability to sus-
tain that attention and maintain a behavioural response consistently and the ability to
selectively maintain attention when distractions are present. Alternating attention means
being able to shift the focus of attention between tasks that require different cognitive
abilities (e.g., composing an email and then answering a phone call). Finally, divided
attention describes the ability to perform multiple tasks or task demands at the same time
(e.g., composing an email while listening to someone on the phone).