AGEING AND ATTENTION: AN
Department of Psychology
Vasanta College for Women,
Attention appears to be the
integral component of most cognitive tasks. It is a necessary component of many
everyday skills such as driving, conversing in noisy environment, searching for
a friend in crowd or interacting with technology (e.g., websites, ATMs). As the
population of older people is growing rapidly, it has become increasingly
necessary to examine how attention function changes with age and to understand
the extent to which these changes can affect their functioning. Measuring
attentional abilities among older adults would allow prediction of continued
success with tasks of everyday life. Some researches have shown that different
types of attention (selective, divided and sustained) decline with ageing when
demands on attentional tasks are increased. This paper presents an overview of
researches done to assess the attentional ability in young and old adults.
Attention, Ageing, Selective
attention, Attentional capacity, sustained attention.
Healthy ageing is
accompanied with a number of cognitive changes. These include decline in
functions such as episodic and working memory, attention and inhibition. Among
these cognitive changes attention is considered to be the fundamental component
as it is gateway to rest of the cognition. Information processing theories of
cognitive ageing suggested that attention deficits could be the source of all or
most age related changes in cognition. Different types of attention (selective,
sustained, and divided) have been found to decline with ageing. Deficiency in
attentional resources has been postulated as important in ageing leading to
inefficiencies rather than losses of functions. It has become increasingly
necessary to examine how attentional ability changes with age and to understand
the extent to which these changes can affect the functioning of rapidly growing
older adult population.
Ageing and Attention
Attention is a necessary
component of everyday skills that require search and prioritization of
information such as driving or interacting with technology (e.g., websites,
ATMs); measuring attentional abilities among older adults would allow prediction
of continued success with tasks of everyday life. Attention is a cognitive
process that helps in complex interaction with the environment by picking up the
relevant information while ignoring the irrelevant ones. Processing one source
of information at the expense of others is the “selective” function of
attention; simultaneous processing of two or more sources of information is the
function of “divided attention” and maintaining a consistent focus on one source
of information is the function of “sustained attention”.
Studies designed to
understand the age related changes underlying attentional abilities show that
normal aging results in loss of attentional capacity 1, 2, 3
typically, the observed effects of aging on attention are modest, and deficits
are apparent only under circumstances of high attentional demands 4, 1, 5.
A number of studies suggested that attention diminishes in old age, as the
tendency for attention to wander begins 2, 6, 7,. For example, one
of the most popular theories used to explain attention and aging, postulates
that with age attention declines because of the increasingly inefficient
operations of an inhibitory mechanism that that helps to suppress irrelevant
information 8, 9. Research on visual attention processes and aging
has focused on selective attention, attentional capacity (divided attention) and
Aging and Selective
Selective attention is the
mechanism in which the resources are directed toward relevant stimuli while
ignoring the irrelevant information in order to meet effectively with task such
as driving, conversing in noisy environment or searching for a friend in crowd.
Visual search task is generally employed to examine the age related attentional
change. Visual search task requires subjects to detect target items in a visual
display. The typical finding in a visual search task is that as the display
size increases, there is a linear increase in RT 10. Previous
researches have reported both deficit as well as age constancies in selective
Evidence for age related
selective attention deficits come from the studies which demonstrated an age
related deficits in the ability to ignore irrelevant or interfering information
11,12,13,14. Rabbit conducted the early investigation for age
differences in selective attention and concluded that older subjects had
difficulty ignoring irrelevant information and were at disadvantage when
searching complex stimuli.11 another study provided further
evidence for age related deficit in selective attention. 13 They
used two conditions of search i.e. feature search and conjunction search and
demonstrated that the older adults were at a disadvantage relative young adults
in the conjunction search condition. Search RT in the feature search condition
was fairly constant over display size for both young and old. It was concluded
that age differences in the conjunction search condition was the result of
increased attentional demands of selecting the appropriate target and avoiding
the interference from similar non target features.
Evidence for age constancies
in selective attention has also been reported. In a study Nabes compared young
and old adults who were required to respond “yes” or “no” regarding the presence
of a prespecified target in a visual display of six digits. 15 On
half of the trials a valid visual cue was presented 1sec. prior to the display
onset and on remaining half of the trail an invalid cue was presented 1sec.
prior to the display onset. Result demonstrated that decrease in RT associated
with cue was equivalent for both young and older adults suggesting that the
older adults were as effective as the young adults in using the cue to attend
selectively to the relevant display items 16. Thus, advance
knowledge about target location can reduce the negative impact of distracters of
Aging and Attentional
Attentional capacity refers
to the limited amount of processing resources that underlie task performance
16. With regard to attentional capacity researches have focused on
divided attention or dual task performance. It has been assumed that the need
to divide the limited pool of attentional resource between two task is more
detrimental for older than to younger adults due to a reduction in cognitive
resource with increasing age.
Dual tasks have been used to
investigate age related changes in attentional capacity. The findings from such
studies have demonstrated that the impairment of performance associated with
dual condition is greater for older adults than for young adults 17.
Numerous studies in cognitive aging research have shown that as the complexity
of the task increases, the magnitude of the age difference in performance also
increases 18, 19, 20, 21. Nestor, Parsuraman and Haxby used probe RT
task paradigm in young and old adults to evaluate the “cost” of both automatic
and controlled mental processes. Results demonstrated that older adults showed
increased attentional cost for both automatic and effortful mental operations
compared to young adults.
These results can be
explained from the assumption that there is fundamental resource (cognitive
capacity) and this resource is reduced in old age. Dual tasks require division
of attention between two simultaneous tasks. If cognitive capacity of elderly
subjects is reduced, then primary task requires greater proportion of the
available resource leaving less for secondary task and thus leading to poorer
secondary task performance in older tan in young adults.
Ageing and Sustained
Sustained attention or
vigilance refers to the ability to detect small changes occurring at random
intervals in the environment 22. The fundamental problem with
sustained attention or vigilance is the decrement function. Vigilance decrement
is the decline in the detection rate of critical targets with time on task.
Studies of sustained attention distinguish between overall vigilance, reflecting
overall level of performance on sustained attention task, and the vigilance
decrement, reflecting the ability to sustain attention over time on task 23.
Laboratory studies of
sustained attention in older persons yielded conflicting results. Several
studies found that sustained attention of young and older persons on vigilance
tests did not differ 24, 25, 26, 27, and 28; while other studies
showed that the vigilance performance of elder person was less efficient than
that of younger persons 29, 30, 31, 32, 33, 34.
The clock test for 1 hour to
study sustained attention in normal aging and found overall decrease in
detection (hits) rates in old relative to young subjects.32 older
subjects had equivalent increase in response time than young subjects. Several
studies indicate that aging is generally associated with increase in response
criteria 35, 36, and that older subjects become more conservative
over time on task than the young. Pars Raman, Nestor and Greenwood 37
used the vigilance task with degraded stimuli while Berardi, Parsuraman, and
Haxby 3 used high event rate digit discrimination task at six levels
of stimulus degradation to investigated age differences in sustained attention.
These studies provided evidence in support of the view that overall level of
sustained attention are lower in older individuals than they are in young
individuals as the processing demands of vigilance tests are increased by
varying event rate and stimulus degradation.
Researchers have explained
this inconsistency in findings regarding sustained attention and aging as the
result of a number of factors. Researches suggested that the rate of stimulus
presentation and the stimulus quality influence performance significantly among
older individuals 38, 39, 1, 37, 40.
explanations have been proposed for age differences in attentional processes and
age related differences in attentional functioning. 41 The first
theory proposes that with increased age comes a reduction in energy that fuels
cognitive processing. Thus, attention is a resource that enables cognitive
processing and this resource is diminished with advanced age. Second theory
proposes that older adult exhibit reduced inhibitory functioning. 42
Attentional deficiencies in older adults are due to a filtering decrement,
resulting in increased levels of intrusions and distractions from irrelevant
stimuli. The third theoretical consideration explains age differences in
attention by a generalized slowing model or by the consideration of a reduction
in the size of older adult’s functional visual field 43. Those who
posit a generalized age related slowing argue that age related attentional
effects are expressions of a general slowing of all cognitive operations with
advanced age 18, 42, 19, 45.
In summary, it can be
concluded that attentional capacity is affected by ageing which is manifested in
terms of inefficiencies in their functioning. Typically, the observed effects
of aging on attention are modest, and deficits are apparent only under
circumstances of high attentional demands. Selective attention seems to decline
with ageing but advance knowledge about target location can reduces the negative
impact of distracters. An attentional capacity or divided attention appears to
be most affected by the ageing process while studies of sustained attention in
older persons yielded conflicting results. The inconsistencies in the findings
can be attributed to differences in methodologies used in different researches.
Various theoretical accounts have also been proposed to explain these results
but this area needs more extensive explorations to understand the changes in
attention as the person grows older.
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