It is well documented that explicit (declarative, conscious) memory declines in normal aging. Studies have shown a progressive reduction in this form of memory with age, and healthy older adults (typically aged 65+ years) usually perform worse than younger adults (typically aged 18–30 years) on laboratory tests of explicit memory such as recall and recognition. In contrast, it is less clear whether implicit (procedural, unconscious) memory declines or remains stable in normal aging. Implicit memory is evident when previous experiences affect (e.g., facilitate) performance on tasks that do not require conscious recollection of those experiences. This can manifest in rehearsed motor skills, such as playing a musical instrument, but is typically indexed in the laboratory by the greater ease with which previously studied information is processed relative to non-studied information (e.g., repetition priming). While a vast amount of research has accumulated to suggest that implicit memory remains relatively stable over the adult lifespan, and is similar in samples of young and older adults, other studies have in contrast revealed that implicit memory is subject to age-related decline. Improving methods for determining whether implicit memory declines or remains stable with age is an important goal for future research, as the issue not only has significant implications for an aging society regarding interventions likely to ameliorate the effects of age-related explicit memory decline, but can also inform our theoretical understanding of human memory systems.
Emma V. Ward and David R. Shanks
Zoltan Dienes and Anil K. Seth
The major theories of consciousness that distinguish conscious from unconscious states can be grouped into two main classes, either higher-order or integration theories. There is evidence that different types of mental states can be unconscious, though that conclusion depends on the theory of consciousness assumed. Unconscious memory (in the sense of the influence of a prior event not recollected) can shape perception and liking and control our behavior. Subliminal perception can produce semantic priming and guide attention and decision making; and optical variables that a person describes incorrectly can guide action. Implicit learning can shape judgments and choices in complex environments. Unconscious intentions can allow people to respond appropriately in goal-directed ways while the person experiences the actions as involuntary. Unconscious attitudes are no more or less plausible than any other mental state being unconscious, but it has been hard to obtain evidence for unconscious attitudes as distinct from gut reactions one does not agree with.