Exploring the Nuances of Memory Decline in Older Age: A Closer Look at Theories and Real-World Functioning 


Memory, the intricate process of encoding, storing, and retrieving information, is a fascinating aspect of cognitive function that evolves throughout our lives. It is categorized into various types, each with distinct attributes, such as sensory, short-term, working, and long-term (implicit and explicit) memory (Kaplan et al, 2016; Martin & Carlson, 2019). In this exploration of the aging mind, we delve into the contrasting theories of memory decline in older adults, examining the Processing Speed Theory and the age-invariant implicit memory hypothesis.

Processing Speed Theory

Salthouse’s (1996) Processing Speed Theory posits that cognitive decline in older adults is primarily attributed to a slowing in the processing speed of cognitive functions like reasoning, problem-solving, and memory. While Salthouse faced criticism for not adequately addressing motor speed confounds in initial experiments (Ebaid et al, 2017), subsequent research has lent support to his theory. Studies linking executive function slowdowns, especially in dual processing speed within working memory, to older adults (Park, 2000; Zacks et al., 2000) reinforce Salthouse’s claims.

However, the real-world applicability of Salthouse’s theory is questionable, as observed in septuagenarian heads of state, industry leaders, and emeriti professors who continue to exhibit exemplary cognitive functioning (Salthouse, 2011). The discrepancy between laboratory findings and everyday cognitive performance raises intriguing questions, urging further exploration to bridge this gap (Salthouse, 2011).

Age-Invariant Implicit Memory

In contrast, the age-invariant implicit memory hypothesis suggests that certain memory processes, particularly implicit memory, remain relatively preserved with age due to their occurrence outside of conscious awareness (Martin et al, 2019; Schacter, 1987). Implicit memory encompasses priming, conditioning, and procedural memory, where learned information aids in task performance without relying on conscious recollection.

Fleischman et al (2004) investigated this hypothesis, finding only mildly reduced priming in older adults but concluding that it was not an inevitable consequence of aging. Similarly, Spaan and Raaijmakers (2011) observed no age-related effects on priming in a study involving cognitively healthy individuals aged 55–94 years.


While some studies, such as Ward et al’s (2013) literature review, suggest that improved measurement methods may reveal age-related effects on implicit memory, the lab-life dichotomy persists. The discrepancy between laboratory findings and real-world cognitive functioning raises intriguing questions about the applicability of these theories in understanding memory decline in older age.

In conclusion, the evidence from laboratory testing supports observable slowing in broad cognitive functions in older adults. Still, the real-world scenario challenges the inevitability of memory decline. Implicit memory, on the other hand, appears to show little to no age-related decline, further complicating the narrative. Ultimately, the exploration of memory decline in older age is a complex journey, requiring a nuanced understanding of both theoretical frameworks and the everyday experiences of older adults.


Ebaid, D., Crewther, S. G., MacCalman, K., Brown, A., and Crewther, D. P. (2017). Cognitive processing speed across the lifespan: beyond the influence of motor speed. Front. Aging Neurosci. 9:62. doi: 10.3389/fnagi.2017.00062 

Fleischman, D. A., Wilson, R. S., Gabrieli, J. D. E., Bienias, J. L., & Bennett, D. A. (2004). A Longitudinal Study of Implicit and Explicit Memory in Old Persons. Psychology and Aging, 19(4), 617–625. https://doi.org/10.1037/0882-7974.19.4.61

Graham, E.K., James, B.D., Jackson, K.L., Willroth, E.M., Boyle, P., Wilson, R., Bennett, D.A., Mroczek, D.K. (2020). Journals of Gerontology Series B: Psychological Sciences and Social Sciences. https://doi.org/10.1093/geronb/gbaa135 

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