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CHAPTER 5
Cognitive ageing in older workers and its impact on lifelong learning 95

hold as well as on the way information is stored and organised. A basic
distinction is that between short-term and long-term memory. Short-term
memory involves immediate recall of items, has a capacity of 7±2 items and
is commonly used when attempting to memorise a short list of items. While
long-term memory involves permanent storage of information in an organised
ʻmental lexiconʼ, it is unlimited in capacity and often described as a library of
knowledge encoded and stored in a relevant and meaningful individual
manner, to be recalled later. Working memory is a theoretical concept first
described by (Atkinson and Shiffrin, 1968) that involves ability actively to hold
relevant information to perform a complex task such as problem-solving and
reasoning. The working memory system (Baddeley, 1999) includes a central
executive that organises sensory input with assistance of attentional
mechanisms, a visuo-spatial sketchpad (for non-verbal information) and a
phonological loop (for verbal information).
Long-term memory is further separated into episodic, semantic and
procedural memories, which involve events, meanings and procedures
respectively. Although long-term memory is unlimited most times healthy
individuals fail to retrieve information accurately. Mnemonic strategies may
reduce forgetting but memory failures are the rule rather than the exception
in everyday situations. The reasons for forgetting have been extensively
investigated due to the importance of memory in personal and professional
environments. Most people in middle adulthood complain that they can not
recall substantial information on processes, procedures and events and are
forced to use reminders to improve their memories. The most important
reasons for forgetting are:
(a) encoding specificity (Thomson and Tulving, 1970);
(b) decay (Woodworth, 1938);
(c) lack of access because of emotional load or repressure (Baddeley, 1999);
(d) interference (Barnes and Underwood, 1959);
(e) amnesia (Baddeley, 1970).
Given the importance of memory in daily activities, several authors have
discussed memory deficits resulting from normal ageing (Gregoire and
Van der Linden, 1997). The studies yielded contradictory results. Table 5.1
provides an overview of the main findings of more recent studies on memory
and ageing in non-pathological individuals.
From Table 5.1 it is clear there are substantial differences in results
depending on age groups and the task used. In relation to short-term memory
which involves immediate recall of short lists of digits there is small decline
that accelerates after the age of 70. On the other hand, well-practiced tasks