Long-term Effects of Cognitive Training

Abstract

Human development is a multidimensional, multidirectional, and multifunctional process that continues throughout the life span. In this process, individuals experience changes in various domains of development. Changes in cognitive functioning have become the focus of aging researchers since cognitive functioning is a main dimension of older adults’ quality of life. Cognitive decline is associated with aging. Thus, interest in cognitive training interventions designed to improve older adults’ cognitive performance has risen significantly. Different formats of cognitive training programmes such as formal cognitive training, collaborative training, group training, and booster training have been used to help older adults prevent cognitive decline and improve their cognitive functioning. Research has revealed that cognitive training has long-term effects. It seems that some cognitive training interventions have longer effects than other programmes. This paper will discuss the significance of cognitive training for older adults’ cognitive performance, the effects of different formats of cognitive training interventions, and whether cognitive training interventions have long-term benefits for older adults.

Key words: aging, cognitive functioning, cognitive training, long-term benefits

Higher incidences of age-related declines in cognitive performance have been reported with the increase of aging population (Thompson & Foth, 2005). Whereas development is characterized by structural growth, increased environmental adaptation, and improved functions, aging is related to structural decay and functional declines (Perlmutter & Hall, 1992). Many have believed that age-related cognitive decline is universal, pervasive, and irreversible change in cognitive performance; however, recent research and theoretical perspectives of human development and aging have changed these beliefs. Some developmental theorists (e.g., Baltes, 1987) have argued that life-span development is a multidimensional, multidirectional, and multifunctional process wherein individuals experience both gains and losses.

Changes in cognitive functioning have become a key area of research in the field of life-span development, especially the question of how changes in cognitive functioning impact the daily performance of older adults. In addition, investigations explored the ability of older adults to improve their performance through cognitive training (Willis & Nesselroade, 1990; Verhaeghen, Marcoen, & Goossens, 1992).

Investigating older adults’ cognitive performance is a challenge for various reasons. Cross-sectional comparisons (comparing young and older adults) of cognitive performance have shown significant differences, but they do not distinguish between age differences and cohort effects (Thompson & Foth, 2005). Longitudinal studies, on the other hand, have provided evidence for greater stability of cognitive performance in adults. Nevertheless, these studies have not separated the confound effect of time of measurement. Alternatively, sequential research designs have overcome the problems appeared in both cross-sectional and longitudinal designs (Thompson & Foth, 2005).

This paper will first discuss the importance of cognitive training for older adults’ cognitive performance. Second, it will compare formats of cognitive training interventions. Third, it will discuss whether improvements of cognitive performance gained through cognitive training have long-term benefits for older adults.

Cognitive training

A growing number of studies have suggested that cognitive decline, particularly in older adults, can be improved by using cognitive training programmes (Thompson & Foth, 2005; Margrett & Willis, 2006). These approaches comprise different conceptual or theoretical frameworks as well as experimental procedures such as formal cognitive training, collaborative training, and group training.  A wealth of evidence shows improvement in cognitive functioning by using these approaches (Margrett & Willis, 2006).

Studies of cognitive training in older adults have focused mostly on cognitive abilities such as memory, reasoning, speed of processing, and spatial orientation that are important for daily functioning. Memory decline is a major issue of aging population; therefore, some have developed training programmes to improve memory skills in older adults (Thompson & Foth, 2005). Cognitive-Behavioral Model of Everyday Memory (CBMEM) (McDougall, 1999), for example, is a programme of memory improvement that includes components such as health promotion, stress inoculation, memory self-efficacy, and memory strategy training. The Memory Improvement Training Programme developed by Mohs and colleagues (1998) includes sections such as the way the individual’s memory works, stages of remembering processes, attention and concentration, making remembering easier, remembering text information, practice makes perfect, remembering faces and names, and maintenance of memory improvement. A meta-analysis of studies revealed that older adults’ memory have been improved through mnemonic training (Verhaeghen, Marcoen, & Goossens, 1992).

Fluid intelligence is another important cognitive ability examined by researchers in relation to older adults’ cognitive performance. It appears that cognitive training has a significant impact on improving fluid intelligence in older adults. A study by Baltes and Willis (1982) examined three aspects of fluid intelligence: figure relations, induction, and attention/memory and found significant improvements in these cognitive abilities after the training intervention. Research also revealed that older adults who received cognitive training exhibited a significant improvement in inductive reasoning (Boron, Turiano, Willis, & Schaie, 2007). Also, a considerable amount of research provided evidence for the positive effects of cognitive training on older adults’ cognitive performance (e.g., Cavallini, Pagnin, & Vecchi, 2003; McDougall, 2000; Brum, Forlenza, & Yassuda, 2009; Kueider, Parisi, Gross, & Rebok, 2012; Lampit, Valenzuela, & Gates, 2015) suggesting that cognitive declines in healthy older adults can be improved through cognitive training intervention.

Different formats of cognitive training

Researchers have used different formats of cognitive training intervention programmes: formal cognitive training, collaborative training, group training, and booster training. In formal cognitive training, researchers use multiple training sessions intended to train certain cognitive strategies (Margrett & Willis, 2006).  The highly structured sessions focus on teaching strategies, practicing these strategies with the trainer’s feedback, and evaluating the targeted cognitive abilities. Many studies of formal cognitive training sessions have revealed significant findings in relation to the improvement in cognitive abilities such as verbal memory, inductive reasoning, and speed of processing (Margrett & Willis, 2006).

Collaborative training is also considered as effective for older adults. There is evidence for effectiveness of collaborative cognitive training intervention in older adults’ cognitive functioning, particularly improving their social-advice giving, understanding everyday printed materials, and everyday life management (Margrett & Masiske, 2002). The partner familiarity was a significant factor that influenced the collaborative training process as well as the outcomes of the collaborative training (e.g., Gould, Osborn, Krein, & Mortenson, 2002; Margrett & Masiske, 2002). For example, familiar dyads benefited more from the collaborative training intervention than unfamiliar older dyads even though the unfamiliar dyads received benefits from collaborating with the other partner on everyday cognitive functioning (Margrett & Marsiske, 2002). However, collaborative training may have some negative influences. For example, some studies found that memory recall of older adults who were in the collaborative training condition, decreased compared to those who were in the individual training condition (Andersoon & Ronnberg, 1995, 1996). Time that participants spent on collaborative training, their efforts during the collaborative training, and social aspects of the given task might have obstructed recall strategies they used. Research has found mixed effects of collaborative cognitive training on older adults’ cognitive performance. It seems that various factors may affect older adults to gain benefits from the collaborative cognitive training intervention.

Some researchers have used both formal and collaborative cognitive training interventions to compare their effects. Margrett and Willis (2006), for example, examined their effects on inductive reasoning ability in older adults. Inductive reasoning can be described as one’s ability to infer general rules from particular instances of serial tasks and to generate the next component in a series. A series of ten training sessions used three measures of inductive reasoning: Letter Series test, Word Series test, and Letter Sets test. The participants were randomly assigned to the individual cognitive training group, the collaborative cognitive training group, and the questionnaire only control group. All participants completed a three hour pretest group session and a two hour immediate posttest group session. The improvement of older adults was assessed using two methods: number of correct items and accuracy of responses. Findings suggested that older adults in both individual and collaborative cognitive training conditions performed better on the Letter Series test and the Word Series test than those who were in the control group at the posttest assessment. However, there was no significant difference between the older adults who participated in the individual training sessions and those who underwent collaborative training sessions. The researchers assumed that collaborative training would be more beneficial for older adults, however; the findings did not confirm this prediction.

Additionally, some have proposed that pretraining sessions (e.g., training in imagery and relaxation training) are advantageous (e.g., Verhaeghen et al., 1992; Brooks et al., 1999), while others have introduced booster sessions after the initial training intervention programme to maintain the cognitive improvement gained through the cognitive training intervention. There are some benefits of booster training sessions (e.g., McDougall, 1999; Willis et al., 2006). For example, a study on long-term effects of cognitive training on older adults’ cognitive abilities and their daily functioning indicated that booster training sessions had a significantly greater influence on improving certain cognitive abilities in older adults (Willis et al., 2006). In this study, the researchers focused on improving older adults’ memory, reasoning, and speed of processing. They used three training interventions to improve these cognitive abilities. Each intervention comprised ten training sessions. In addition to the initial training intervention, the researchers used four booster training sessions. Findings suggested that older adults who received booster training sessions performed significantly better on speed of processing than those who did not receive booster training. However, other studies found no significant benefits of booster sessions (e.g., Scogin, Prohaska, & Weeks, 1998).

Instructional formats such as group sessions and self-instructional training have also been evaluated (Thompson & Foth, 2005). Some have demonstrated that group sessions are helpful (e.g., Verhaeghen et al., 1992), whereas others have found no special benefit of these sessions (e.g., Rasmusson, Rebok, Bylsma, & Brandt, 1999). Self-instructional training sessions have also been used to understand the effects of cognitive training on older adults’ cognitive abilities (e.g., Flynn & Storandt, 1990). Moreover, some have used combined strategies (group sessions and self-instructional training). Although some studies found that different formats influenced results, there is no consistent evidence to prefer one particular format over another (Thompson & Foth, 2005).

Long-term effects of cognitive training

One of the main concerns of aging researchers is to understand whether the cognitive training intervention has long-term effects on older adults’ cognitive performance. Some studies have revealed that cognitive training has long-term effects. A study of fluid ability training by Willis and Nesselroade (1990) suggested a significant long-term benefit on intellectual performance in older adults. In this research, older adults participated in three experimental phases in cognitive training that related to fluid ability of figure relations. Each phase included pretest-treatment-posttest/no-treatment control group design. The first phase conducted in 1979, aimed to examine the effects of cognitive training on mental ability performance. In the second phase, one year later, the researchers provided further cognitive training. The third phase, in 1986, intended to evaluate the long-term maintenance of training effects and to understand whether older adults would benefit from the additional training. The older adults received five hour training in the first and the second phase. In the third phase, the researchers limited the training sessions for two hours because of advanced age and the limitations of older adults’ visual perception. This cognitive training programme focused on the fluid ability of figural relations, as described by tasks of identifying rules or patterns in figure material. The programme was based on a task analysis of Scale 2 of the Culture Fair Test (Cattell & Cattell, 1957), which is considered a strong marker of the ability of figural relations. It includes four subtests: Figure Series, Figure Classify, Matrices, and Topology, which examine different aspects of figural relations. The task analysis recognizes relational rules such as shape, size, and position used in solving items in each subtest. The fluid ability training problems were created for rules related to each subtest. The training sessions in this study (Willis & Nesselroade, 1990) examined, included the following: a) modeling the use of relational rules in solving the task by the trainer, b) individual practice by older adults on training items, c) providing feedback regarding correct solutions of practice problems, and d) a group discussion.

Findings revealed that the cognitive training programme enabled many adults in the old-old age group to perform higher level of figural relations ability than individuals in young-old age group. Results further suggested that considerable plasticity could be observed in cognitive functioning even in old-old age. Older adults in their late seventies exhibited significant cognitive improvement after the cognitive training intervention. Moreover, the magnitude of training improvement occurred in two phases. Researchers also observed high performance in later phases of the cognitive training programme as a result of cumulative effects.

Willis and Nesselroade’s study (1990) provided significant evidence for the long-term effects of cognitive training on cognitive performance in older adults specifically, in old-old age. However, several concerns should be considered when interpreting the findings. One is, the older adults in this study reported that they were in good health; therefore, the cognitive training intervention may not be effective for older adults who have cognitive changes or decline due to neuropathological conditions. Next, the participants were community-dwelling adults who might have had low levels of cognitive functioning due to limited cognitive stimuli in their everyday setting. Cognitive stimulation in the environment and maintaining engagement in cognitively stimulating activities are important in enhancing and maintaining cognitive performance in old age (Scarmeas, Levy, Tang, Manly, & Stern, 2001; Ball et al., 2002; Wilson et al., 2002). Even though the findings of this study revealed that cognitive training intervention improved older adults’ cognitive performance, it is questionable whether these older adults would be able to maintain the improved cognitive ability gained through the training programme if they continue to live in the same environment that does not provide cognitive stimulation. Another question is how older adults would perform in naturalistic types of cognitive activities. This study utilized an experiment to examine the long-term effects of fluid ability training on older adults’ cognitive performance, thus, it is important to investigate the methods of enhancing older adults’ cognitive performance in more natural type of activities that they can use in their everyday functioning.

Some researchers have investigated whether computer-assisted cognitive training has an effect on long-term improvement in cognitive performance in older adults. Gunther and colleagues (2003), for example, examined the effects of computer-assisted cognitive training on aging-related memory failures, learning, information processing speed, and interference tendency in older adults. In this study, a sample of 19 older adults received 14 weeks computer-assisted cognitive training that included one 45-minute training session per week. These older adults completed or responded to the Nurnberg Aging Inventory and the California Verbal Learning Test prior to the training programme, immediately after the training programme, and five months after the training.

After the computer-assisted cognitive training, Gunther et al. (2003) observed significant improvements in most cognitive abilities in these older adults. Particularly, they exhibited significant improvements in primary working memory, secondary working memory, learning, interference tendency, and information processing speed. In addition, the researchers found that older adults maintained cognitive abilities such as learning and interference tendency five months after they completed the cognitive training. This suggests that older adults improved cognitive abilities that were targeted through the computer-assisted training programme, yet, they were unable to maintain all the cognitive abilities for five months. A limitation of this research work is that there was no follow-up after five months to examine whether older adults were able to maintain those improved cognitive abilities. Therefore, it does not provide strong evidence for long-term effects of computer-assisted cognitive training on maintaining certain cognitive abilities in older adults.

Inductive reasoning is another cognitive ability investigated by aging researchers in relation to older adults’ cognitive functioning. It involves one’s ability to recognize novel patterns and to effectively use these patterns to solve similar problems (Boron, Turiano, Willis, & Schaie, 2007). Inductive reasoning is an important cognitive ability that can be examined both experimentally and descriptively as it is related to higher order executive functioning. Also, it is considered as a pure marker of fluid intelligence. As a fluid ability, inductive reasoning seems to be vulnerable to earlier age-related declines. Particularly, it is associated with the ability in performing tasks of daily living among older adults (Wolinsky et al., 2006).

Research finds that cognitive training has significant effect on older adults’ reasoning ability. For example, a study by Boron et al. (2007) examined the effects of cognitive training on accuracy and the number of items that older adults attempted in inductive reasoning performance. In this study, older adults received two cognitive training interventions: inductive reasoning training and spatial orientation training. Older adults who received the spatial orientation training served as a comparison group. Both these training interventions targeted the content and strategies unique to inductive reasoning and spatial orientation. After the baseline assessment, older adults received five one-hour training sessions within two weeks period. They were administered the Primary Mental Ability (PMA) reasoning (inductive reasoning) and spatial orientation measures at pretest and posttest assessments. Findings suggested that older adults who received inductive reasoning training answered more items in the measures, and answered more of them correctly. Lower functioning older adults (those who have a lower level of education) and those who performed at a lower baseline level due to cognitive decline exhibited greater magnitude of change in accuracy as a function of cognitive training compared to those who exhibited higher functioning. Even though the findings supported the effects of cognitive training on improvement in older adults’ inductive reasoning, it did not provide adequate information regarding whether these older adults maintained the improved cognitive ability for a longer period. In addition, several factors limited the generalizability of findings in this study. The sample of this study included independently functioning Caucasian older adults who were selected from a geographically restricted region. Moreover, they were screened on the basis of their physicians’ reports to ensure their physical and mental health. These factors had led to a selected sample, thereby limiting the generalizability of the findings of this study.

Another study provided evidence for the long-term effects of cognitive training on older adults’ figure relations performance (Willis, Blieszner, & Baltes, 1981). In this study, a sample of 58 older adults (61-84 years old) was randomly assigned to two groups: the figure relations training group and the control group. After the baseline assessment, these older adults were assessed at three posttests conducted after one week, one month, and six months after the cognitive training intervention. Fluid and crystallized measures were used in posttest assessments to evaluate the effects of cognitive training on older adults’ cognitive functioning. The cognitive training programme consisted of five one-hour training sessions over two weeks. The training programme was based on the task analysis of Scale 2 of the Culture Fair Test (Cattell & Cattell, 1957). Each of the first four cognitive training sessions focused on one of the four types of figure relation problems: Figure Series, Figure Classify, Matrices, and Topology. The fifth cognitive training session aimed to review all four types of figure relation problems. In this study, the researchers assessed the effects of cognitive training intervention by using two criteria. The first criterion focused on the cognitive training effects and the transfer effects within a theory-based measurement of paradigm. The second criterion aimed to assess the maintenance of cognitive training and transfer effects across three posttests assessments (one week, one month, and six months). Results revealed significant differences between the training group and the control group on figure relations across three posttests. Also, a pattern of differential transfer was observed with greater training effect, and the pattern of training transfer was maintained across three posttest assessments. Accordingly, the cognitive training intervention had a significant effect on older adults’ cognitive performance and they were able to maintain the improved cognitive ability for six months. However, there was no follow-up after six months.

Some studies have indicated that the improvement in cognitive performance of older adults has lasted a longer period (e.g., several years) after the cognitive training (e.g., Schaie, 1993; Stigsdotter, Neely, & Backman, 1993), whereas others have not found strong evidence for the long-term effects of cognitive training intervention. For example, a study by Schmidt, Berg, and Deelman (2001) stated that cognitive improvement in older adults after the training intervention did not last for three months. In this study, the researchers investigated the effects of the cognitive training programme on prospective memory in adults. Prospective memory can be described as remembering to perform or do something in a particular situation or at a specific moment in the future. It is an important aspect of memory that individuals use more frequently in their daily lives (Schmidt, Berg, & Deelman, 2001).

Using the cognitive training intervention, the researchers intended to enhance individuals’ prospective memory by relating cues from the retrieval situation with the information that needs to be remembered. In this study, a sample of adults over 45 years of age was randomly assigned to three conditions: the prospective training, the educational training, and the control condition. The prospective and the educational trainings consisted of six sessions, each of which lasted about an hour. During the prospective training sessions, the researchers focused on both external and internal strategies that would benefit adults to improve their prospective memory. The educational training sessions aimed to discuss about ways that adults can reduce worries about forgetfulness. In each session, they discussed about a topic associated with memory. These adults underwent an individual training during the training intervention and they were given homework after each training session to practice their abilities further in daily settings. They were assessed for prospective memory in three occasions: before the training period, after the training period, and three months follow-up. The measurements included a telephone task, a prospective categorization task, and a prospective memory task (name-face test, names in context I, names in context II, and famous faces). The outcomes of the training were assessed through subjective as well as objective evaluations. With regard to subjective evaluations, it was found that adults were satisfied with the effects of the training in both conditions: the prospective training condition and the educational training condition. Findings suggested that the prospective training had a significant effect on prospective memory measures at posttest assessment. Even though training had a significant effect, there was only a small improvement on prospective memory performance. A separate analysis of results of both the telephone task and the prospective categorization task revealed no significant overall training effect. However, older participants in the training group improved most on the telephone task. There was no significant training effect on the prospective categorization task. Findings suggested that the training-related performance improvement was maintained till three months after the initial training. The effects of the cognitive training did not generalize to other memory measures that were assessed with tests for remembering names or control measures that were assessed with visuomotor reaction time tests. Similar to previous research, this study does not provide strong evidence for long-term training effects on prospective memory performance in older adults even though the older adults reported subjective satisfaction with the training. In addition, there was no evidence whether the improved cognitive ability was maintained after the three months of follow-up.

A study on the effect of cognitive training on speed of processing in older adults found significant effects only on instrumental activities of daily living (Edwards et al., 2002). In this study, the researchers aimed to examine the extent to which standardized speed of processing training intervention transfers to similar and different speeded cognitive assessments and also to other aspects of cognitive performance. A sample of community-dwelling older adults who were randomly assigned to the training group (speed of processing) and the control group were tested on cognitive skills such as speed of processing, executive function, memory, visual-spatial skills, crystallized intelligence, attention, verbal fluency, and functional abilities. The training group received ten one-hour training speed of processing and they completed the same tests six weeks after the initial training. Findings suggested that the training intervention had significant effects on some measures of speed of processing but did not transfer to all domains of cognitive performance. The older adults who received the cognitive training performed significantly better at posttest on the Useful Field of View (speed of processing) than the control group. Useful Field of View measures the speed at which an individual can process multiple stimuli rapidly in the visual field (Edwards et al., 2002). Older adults also performed better on Instrumental Activities of Daily Living (IADL) functions than the control group, that is, training of speed of processing had a transfer of the training effect to IADL functioning. These findings suggest that cognitive training has long-term effects on improving certain domains of cognitive functioning. Again, there was no evidence to support whether the improved cognitive performance was maintained after six weeks. Therefore, it is not clear whether older adults were able to continue their improved ability over longer period of time.

A study by Dahlin and colleagues (2008) examined the long-term effects of computer-based cognitive training on improving executive functioning in both young and older healthy adults. In this study, older adults were randomly assigned to two conditions: the training group and the control group. Young adults were randomly assigned to the same conditions. They underwent a computer-based cognitive training in updating of information in working memory.  The training intervention included 15 sessions over a period of five weeks, with three sessions of 45 minutes each per week. They were trained in groups of four. The cognitive training session comprised practice on the criterion task (the letter memory task) and five training tasks. All these tasks need updating of information. Of the five training tasks, four were similar to the criterion task which needed updating of single items such as letters, numbers, colors, and spatial locations). The other training task, the keep-track task, also needed updating, categorization, and association. All participants were assessed at pretest, and again at posttests immediately after the completion of the cognitive training intervention and 18 months after the cognitive training. Measures included cognitive abilities such as working memory, episodic memory, perceptual speed, verbal fluency, and reasoning.

With respect to older adults, findings revealed a significant improvement in cognitive performance (the letter memory criterion task) suggesting cognitive training gains. More specifically, their cognitive gains were similar to or even larger than that of young adults. Except the keep-track task, in all other tasks, older adults exhibited significant improvement in cognitive performance suggesting considerable and long-lasting plasticity of executive functioning in old age. However, the study did not extend beyond 18 months.

Cognitive training on older adults’ daily functioning

Cognitive decline affects everyday functioning in older adults. Researchers investigated the effects of cognitive decline on older adults’ Instrumental Activities of Daily Living (IADL) (e.g., cooking, shopping, travelling) and whether the cognitive training would be beneficial for their cognitive performance. For example, Willis and colleagues (2006) investigated the long-term effects of cognitive training on cognitive abilities as well as everyday functioning in older adults. This study was a five-year follow-up study with four groups: three treatment groups and a control group conducted between April 1998 and December 2004. Older adults were assessed at baseline, following the training and annually (1, 2, 3, and 5 years). Three training interventions targeted to assess three cognitive abilities: memory (verbal episodic memory), reasoning (inductive reasoning), and speed of processing (visual search and identification). Each training intervention comprised 10 training sessions. In addition, the researchers conducted four booster training sessions at 11 and 35 months after the initial training sessions. The major purpose of these booster training sessions was to maintain cognitive improvement gained through the training sessions.

Cognitive outcomes such as reasoning, memory, and attentional speed were used to evaluate the effects of the cognitive training intervention and functional outcomes such as everyday problem solving, activities of daily living (ADL), instrumental activities of daily living (IADL) functioning, and everyday speed of processing. Considering the training effects of cognitive abilities, findings revealed that each training intervention produced immediate improvement in cognitive skills. Also, the improvements were maintained across five years. With regard to the effects of the training intervention on daily functioning, results were analyzed using self-reported instrumental activities of daily living measures and performance-based measures. Results of self-reported measures indicated that even though older adults in all three training groups stated that they had less difficulty in instrumental activities of daily living (IADL) the effect of findings was significant only for the reasoning group. Findings of performance-based IADL measures suggested that there was no general effect on daily problem solving or daily speed of processing. The older adults who had the booster training in speed of processing exhibited better performance than those who did not receive the booster training. Overall, though there were significant findings, there was no strong evidence to support that cognitive training had significant effect on reducing age-related cognitive decline and improving instrumental activities of daily living in older adults.

Conclusion

The major purpose of this paper was to discuss and analyse findings of studies that have focused on long-term effects of cognitive training on older adults’ cognitive performance. Considering the aforementioned studies and their findings, it seems that researchers have found mixed results in relation to the long-term benefits of cognitive training. Reasons for these outcomes may vary from one study to another. Researchers have used different training intervention programmes such as computer-assisted training, individual training, group training, and booster training to examine the long-term effects. In addition, the duration of the cognitive training intervention varies from one study to another (e.g. ten one-hour sessions, six one-hour sessions, and weekly 45-minute sessions). Therefore, these training interventions may have different outcomes in relation to the targeted cognitive abilities. Moreover, the evaluations of the long-term effects of cognitive training were conducted at varying delays. For example, some used three posttest assessments: one week, one month, and six months, after the cognitive training, while others conducted only one posttest assessment. Therefore, it is not clear whether older adults maintained the improved cognitive abilities longer period of time and whether the improvements had long-term benefits.

It is also important to note that the selection of sample might have influenced different outcomes of cognitive interventions. For example, some studies included selected samples, whereas others consisted of community-dwelling older adults who may experience in low levels of cognitive functioning due to limited cognitive stimuli in their living environment. Even though these older adults improved their cognitive abilities through the cognitive training interventions, they may not be able to maintain the improved skills due to lack of cognitive stimulation in their everyday settings. Therefore, the outcomes of these studies did not provide a clear picture of long-term benefits of cognitive training. Another concern is whether these older adults are able to perform in naturalistic types of cognitive activities. Mostly, studies utilized an experimental procedure to examine the long-term effects of cognitive training programmes on older adults’ cognitive performance. They do not provide evidence for how they would perform in more naturalistic type of cognitive activities. Hence, it is vital to focus on improving older adults’ cognitive performance in more naturalistic type of cognitive activities that they can use in their everyday functioning.

In conclusion, researchers have examined different aspects of cognitive performance in older adults using different methods based on the targeted cognitive domains. It is clear that some cognitive training programmes have longer effects than other training interventions. Also, even though cognitive training has immediate cognitive improvements in older adults, they may need additional cognitive training (e.g., booster training sessions) to maintain the improved cognitive abilities. Considering the aforementioned factors and findings, it seems that more research is needed to understand the long-term benefits of cognitive improvements in older adults. It is important to identify specific method or training programme that would be more beneficial for older adults to maintain certain cognitive abilities. More importantly, future research needs a greater focus on improving cognitive abilities that older adults require in their daily functioning and to utilize methods that include more naturalistic types of cognitive activities to enhance their cognitive functioning in everyday setting.

Malathie P. Dissanayake, South Asian Institute of Technology and Medicine

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