Cognitive Decline with Age: What is Affected?

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June 05, 2018 - Gini Beqiri

This article lists key challenges for adult learners due to the natural cognitive decline humans experience as they age.

Intelligence

1. Crystallised intelligence

Consists of the knowledge and skills that have built-up from previous experiences. It is overlearned and well-practiced, such as vocabulary.

This remains intact regardless of your age and adults are better at tasks requiring this intelligence compared to younger people as this knowledge is formed from experiences.

2. Fluid intelligence

Consists of knowledge and skills that have not been accumulated from your experiences and it is less familiar, such as problem-solving. This type of intelligence declines with age so it's important to teach older people strategies to assist them for these tasks.

Attention

Attention is the ability to focus on specific stimuli. There are different types of attention:

Sustained attention: There are no age-related differences in focusing attention on a task over a period of time, for example, watching TV.

Divided attention: This consists of processing multiple stimuli or engaging in multiple tasks simultaneously. This declines with age, especially when the task is more complex. There is evidence that more practice, training and aerobic exercise can help:

• It's thought that more training might help the activity become more automatic and therefore require less attention. Or perhaps the individual has more time to develop better strategies.
• Cardiovascular fitness may increase the effectiveness of neural processes or increase necessary resources (Hawkins, Kramer and Capaldi, 1992).

Selective attention: Attending to specific stimuli in the environment whilst disregarding irrelevant stimuli, such as, trying to talk and listen to someone in a busy restaurant. Selective attention also involves switching attention.

A lot of the original evidence for age-related differences in selective attention came from the Stroop task. This task consists of participants naming the ink colour of an incongruent colour word, for example, the word "yellow" printed in blue. Performance speed declines with age so it's better to avoid overloading adult learners and allow them to fully attend to one task at a time.

Memory

It's well-known that memory is affected by aging but not all types of memory are negatively affected.

Working memory

Working memory involves temporarily holding information in your mind and simultaneously manipulating this information (Baddeley & Hitch, 1974). An example is holding numbers in your head and reorganising them in a certain way. As age increases, working memory declines. This affects learning because it can make tasks, such as, problem-solving and decision-making more difficult.

Emotional working memory

Mikels et al. (2005) found no significant difference between emotional working memory with age. Since emotional working memory does not decline, this suggests that increasing the emotional valence of information may increase memory retention in older adults.

Long-term memory

Long-term memory requires information to be retrieved but this information is not being actively maintained so the original learning could have occurred within the last minutes or many years ago. Long-term memory is important for learning as you want information to remain in your long-term memory.

Declarative (explicit) memory

Declarative memory is the conscious recollection of facts and events in your life. There are different types of declarative memory:

Semantic memory consists of general knowledge about the world, factual information and knowledge of concepts. This type of memory is not affected by age and sometimes older people are better at remembering this information compared to younger people. However, the speed of retrieval may be slower, especially for words and names but this should not interfere that much with learning.

Episodic memory is the memory for personal experiences and events that took place at a certain time and place. This type of memory is the most affected by aging. The impairment with episodic memory and other memory types may be due to the way the information is encoded, consolidated (stored) or retrieved:

Flow of encoding, consolidation and retrieval of information. Diagram from Explore: My Significant Learning

Encoding:

• With age, information may be encoded in a less meaningful way leading to the memory traces not standing out from other memories. This makes retrieval more difficult.
• Salient information may be attended to and less salient information may be ignored, for instance, the context of the experience. This is called source memory as it consists of remembering where and when information was learned - this recollection becomes more difficult with age.
• They may lack effective encoding strategies, for example, they may forget where they placed their notebook. Following a routine reduces this age difference such as, always placing the notebook in the same place. Or using external aids, for example, a list, a calendar or alarm. More time should be taken to actively process new information, such as, discussing it with a peer or creating associations to remember certain facts.
• Divided attention is needed.

Consolidation:

• Aspects of an experience should be connected and formed into a memory trace but this may be impaired if a substantial amount of the experience is associated to its context.

Retrieval:

• Retrieval depends on encoding because information is more difficult to retrieve if it hasn't been encoded effectively.
• Free recall decreases with age but when provided with the appropriate cues information can be retrieved.

Nondeclarative (implicit) memory:

Nondeclarative memories are when there has been a change in your behaviour due to previous experiences but you have no memory of this experience, such as, remembering the words to a song. This type of memory remains stable throughout life.

Procedural memory is a type of nondeclarative memory and it's also not affected by age. It is the memory for cognitive and motor abilities which have been acquired due to practice, such as, riding a bike. This suggests that it's important for learners to practice as much as possible with new information.

Autobiographical memories are personal memories that are episodic and semantic:

• Recent memories are the easiest to retrieve
• The earliest memories are the most difficult to retrieve - the gist of the experience is recalled but fewer details are remembered.
• Memories between the ages of the 15-25 years of age are also more easily recalled. This is referred to the reminiscence bump where the memories are more easily recalled due to the salience and emotionality of that period of life. This again suggests the importance of emotional valence for encoding and retrieving information.

Key points

• Declining working-memory can make some learning processes, such as problem-solving, more difficult.
• There are age-related differences in effective encoding strategies.
• Information may be encoded in a less meaningful way which makes retrieval more difficult.
• Source memory declines and less salient information may not be encoded.
• Using emotional relevance to encode information can decrease the rate of forgetting.
• More time is needed to actively process new information.
• Cues can help with retrieval.
• Practice can assist in making memories and processes easier to recall.
• As age increases, the gist of an experience is remembered but fewer details are recalled.

These memory changes may be due to a slower processing speed, inability to divide attention and the lack of using strategies to improve learning and memory.

Processing speed

Processing speed is the speed cognitive processes and motor responses are performed. This declines with age and lots of cognitive processes are affected due to this. For example, Salthouse (1991) explored age-related decline in cognitive ability by testing 672 people between 20 and 84 years of age.

From the results they concluded that a decline in processing speed mediates the relationship between aging and declining cognitive ability. Therefore, older people need more teaching time because their difficulty is with learning the information adequately for recall - once they have learned the information well enough their recall is not impaired . So it may take longer to teach adults compared to younger people thus they should be given longer teaching time.

Language

Language is made up of both types of intelligence and this ability remains intact, including vocabulary. With age, it becomes more difficult to retrieve words - it takes longer and it becomes more difficult to generate the relevant words quickly (verbal fluency).

Recalling familiar names and places (visual confrontation naming) also becomes difficult from 70 years of age.

Executive control

Executive control consists of a variety of cognitive processes that are involved in selecting and engaging in behaviours appropriate for achieving certain goals, for example, planning, organising, problem-solving, management, implementation and evaluation.

• Executive control is especially needed for novel situations but this ability declines with age due to the decline in mental flexibility.
• There are age-related differences in response inhibition - this is when you stop yourself from engaging in an automatic response and instead produce a more effective novel response.
• Reasoning with unfamiliar information also declines, for example, research suggests that inductive reasoning declines from 45 years old (Singh-Manoux et al., 2012).
• It takes longer for adults to find solutions to problems not experienced previously.

Many of the age differences in cognition seem to be mediated by the decline in working memory which may be due to the decline in processing speed.

What can affect cognitive ability when aging?

Factors linked to aging may also be partially responsible for cognitive decline:

• Health problems: the chance of health problems increases with age and multiple studies have suggested that any physiological disease can negatively affect cognitive function. Hypertension has been especially linked to poorer cognitive functioning and research has suggested that chronic hypertension predicts cognitive decline (Waldstein, 2000).
• Medications which cause side effects, such as tiredness
• Lifestyle factors, for example, smoking, alcohol consumption, dietary insufficiencies, engaging in mentally stimulating activities etc.
• Mental health problems, such as depression which is common in older people, can affect motivation and concentration etc.
• Sensory changes can reduce information processing, for example, reduced hearing ability.
• There are neurobiological explanations of why processing speed decreases. O’Sullivan et al. (2001) suggest that processing speed is due to cortical disconnection - where white matter tracts degrade during aging.

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It's important to understand age-related differences in cognitive abilities because many abilities decline but others remain stable or are even enhanced. With this information you can prepare aptly and create a class or course that suits the needs of your learners.