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Working and ageing
96 Guidance and counselling for mature learners

that involve knowledge (crystallised intelligence) show little or no decline
across the life span. This indicates that life experience and wisdom
compensate for slight changes in memory ability in older adults particularly
over 60 years of age. It is likely that older adults use their experience to adapt
effective strategies while younger people rely more on their processing abilities
and increased memory performance.

5.5. Speed of processing and ageing

Speed in cognitive processing emerges as a unique and reliable predictor of
cognitive ability in adults. Decision speed refers to the ability to respond
accurately and quickly to complex problems that not everyone would be able to
answer if given indefinite time. On the other hand, perceptual speed refers to
the ability to respond quickly to relatively easy tasks that everyone can correctly
answer if given indefinite time (Salthouse, 2000). Age-related delay in speed
can be illustrated with simple reaction time tasks that require an individual to
press a button at the presence of a stimulus. Verbal fluency is another indicator
of speed in linguistic ability, which is a predictor of memory in older adults
(Luszcz, 2000). Speed of processing and general knowledge are both reliable
predictors of memory tasks in older adults (Hedden et al., 2005).
A decline in speed of processing has been documented in several studies
(Salthouse, 2000; Birren and Fisher, 1995). However, this decline is more
evident after the age of 60 and affects other cognitive abilities, such as
memory and reasoning. According to the processing speed theory (Salthouse,
1996) cognitive ability is affected by processing speed because some
cognitive operations can only be successfully completed within a time
framework since the supporting operations may no longer be available if
processing is achieved at a later stage. In essence, speed of processing
reflects not only the ability to perform a specific activity but also the ability to
perform rapidly other tasks that support the target activity. Indeed, slow
processing may reduce the amount of available information needed to perform
a task that requires a higher level of processing. For example, in a complex
task, operations such as associations, elaborations, and rehearsals should
be readily available within a specific time framework to achieve higher
performance. If processing speed delays these supporting operations due to
decay or displacement, performance will be weaker (Salthouse, 1996).
Overall, speed of processing appears to account for several age-related
cognitive deficits. General slowing of processing ability may begin as early as