Would you still be yourself if you didn’t remember what happened to you yesterday? The longer our lives progress, the more of our past we need to remember (or wish to forget). Our ability to remember what happened to us is crucial to our ability to conceptualize ourselves, and in that way, our memories are fundamental to who we are. However, we experience changes to our memories throughout our lives. This section will highlight how memories are typically not remembered from early life, and also how memory changes in old age lead to not only questions about who we are, but how one can go about their activities of daily living.

Memory During Infancy and Childhood

Memory requires the capacity to mentally represent experience, so it should not be surprising that infant memory is rather fleeting and fragile. As a result, older children and adults experience infantile amnesia (sometimes called childhood amnesia), the inability to recall memories from the first few years of life. Several hypotheses have been proposed for this amnesia. From the biological perspective, it has been suggested that infantile amnesia is due to the immaturity of the infant brain, especially those areas that are crucial to the formation of autobiographical memory, such as the hippocampus. From the cognitive perspective, it has been suggested that the lack of linguistic skills of babies and toddlers limit their ability to mentally represent events; thereby, reducing their ability to encode memory. Moreover, even if infants do form such early memories, older children and adults may not be able to access them because they may be employing very different, more linguistically based, retrieval cues than infants used when forming largely photographic or visual memories. Finally, social theorists argue that episodic memories of personal experiences may hinge on an understanding of “self”, something that is clearly lacking in infants and young toddlers.

However, in a series of clever studies Carolyn Rovee-Collier and her colleagues have demonstrated that infants can remember events from their life, even if these memories are short-lived. Three-month-old infants were taught that they could make a mobile hung over their crib shake by kicking their legs. The infants were placed in their crib, on their backs. A ribbon was tied to one foot and the other end to a mobile. At first infants made random movements, but then came to realize that by kicking they could make the mobile shake. After two 9-minute sessions with the mobile, the mobile was removed. One week later the mobile was reintroduced to one group of infants and most of the babies immediately started kicking their legs, indicating that they remembered their prior experience with the mobile. A second group of infants was shown the mobile two weeks later, and the babies made only random movements. The memory had faded (Rovee-Collier, 1987; Giles & Rovee-Collier, 2011). Rovee-Collier and Hayne (1987) found that 3-month-olds could remember the mobile after two weeks if they were shown the mobile and watched it move, even though they were not tied to it. This reminder helped most infants to remember the connection between their kicking and the movement of the mobile. Like many researchers of infant memory, Rovee-Collier (1990) found infant memory to be very context dependent. In other words, the sessions with the mobile and the later retrieval sessions had to be conducted under very similar circumstances or else the babies would not remember their prior experiences with the mobile. For instance, if the first mobile had had yellow blocks with blue letters, but at the later retrieval session the blocks were blue with yellow letters, the babies would not kick.

Infants older than 6 months of age can retain information for longer periods of time; they also need less reminding to retrieve information in memory. Studies of deferred imitation, that is, the imitation of actions after a time delay, can occur as early as six-months of age (Campanella & Rovee-Collier, 2005), but only if infants are allowed to practice the behavior they were shown. By 12 months of age, infants no longer need to practice the behavior in order to retain the memory for four weeks (Klein & Meltzoff, 1999).

During middle childhood, children are able to learn and remember due to an improvement in the ways they attend to and store information. As children enter school and learn more about the world, they develop more categories for concepts and learn more efficient strategies for storing and retrieving information. One significant reason is that they continue to have more experiences on which to tie new information. New experiences are similar to old ones or remind the child of something else about which they know. This helps them file away new experiences more easily.

Memory and Aging

There are many stereotypes regarding older adults– as forgetful and confused, but what does the research on memory and cognition in late adulthood reveal? Memory comes in many types, such as working, episodic, semantic, implicit, and prospective. There are also many processes involved in memory. Thus it should not be a surprise that there are declines in some types of memory and memory processes, while other areas of memory are maintained or even show some improvement with age.

Changes in Working Memory

Working memory is the more active, effortful part of our memory system. Working memory is composed of three major systems: The phonological loop that maintains information about auditory stimuli, the visuospatial sketchpad, that maintains information about visual stimuli, and the central executive, that oversees working memory, allocating resources where needed and monitoring whether cognitive strategies are being effective (Schwartz, 2011).

Schwartz reports that it is the central executive that typically shows the most marked declines with age. In tasks that require allocation of attention between different stimuli, older adults fare worse than do younger adults. In a study by Göthe et al. (2007) older and younger adults were asked to learn two tasks simultaneously. Young adults eventually managed to learn and perform both tasks without any loss in speed and efficiency, although it did take considerable practice. None of the older adults were able to accomplish this. Yet, when asked to learn each task individually, older adults could perform just as well as young adults. Having older adults learn and perform both tasks together was just too taxing for the central executive. In contrast, in working memory tasks that do not require much input from the central executive, such as the digit span test, which predominantly uses the phonological loop, older adults perform on par with young adults (Dixon & Cohen, 2003).

Changes in Long-term Memory

Long-term memory is divided into semantic (knowledge of facts), episodic (memories of specific events), and implicit (stored procedural skills, classical conditioning, and priming) memory. Semantic and episodic memory are part of the explicit memory system, which requires conscious effort to create and retrieve. Several studies consistently reveal that episodic memory shows greater age-related declines than semantic memory (Schwartz, 2011; Spaniol et al., 2006).

It has been suggested that episodic memories may be harder to encode and retrieve because they contain at least two different types of memory: (1) the event and (2) when and where the event took place. In contrast, semantic memories are not tied to any particular geography or time line. Thus, only the knowledge needs to be encoded or retrieved (Schwartz, 2011). Spaniol et al. (2006) found that retrieval of semantic information was considerably faster for both younger and older adults than the retrieval of episodic information, with there being little difference between the two age groups for retrieval of semantic memories. They note that older adults’ poorer performance on episodic memory appeared to be related to slower processing of the information and the difficulty of the task. They found that as tasks became more difficult, the gap between the two age groups’ performance widened, but more so for tasks involving episodic than semantic memory tasks.

Studies that examine general knowledge (semantic memory) of topics such as politics and history (Dixon et al., 2007) or vocabulary/lexical memory (Dahlgren, 1998) often find that older adults outperform younger adults. However, older adults do find that they experience more “blocks” at retrieving information that they know. In other words, they experience more tip-of-the-tongue (TOT) events than do younger adults (Schwartz, 2011). Memory blocks are especially common for the retrieval of “nonsense words”or specific concept labels. Unfortunately for older adults, nonsense words include the names of people, places, and things (like movies, restaurants, or books)– which represent many common topics of conversation.

Implicit memory requires little conscious effort and often involves skills or more habitual patterns of behavior. This type of memory shows few declines with age. Many studies assessing implicit memory measure the effects of priming. Priming refers to changes in behavior as a result of frequent or recent experiences. For example, if you were shown pictures of food and asked to rate their appearance and then later were asked to complete words such as s_ _ p, you may be more likely to write “soup” than “soap” or “ship.” The images of food “primed” your memory for words connected to food. Does this type of memory and learning change with age? The answer is typically “no” for most older adults (Schacter et al., 1994).

Prospective memory refers to remembering things we need to do in the future, such as remembering a doctor’s appointment or to take medication before bedtime. It has been described as “the flip-side of episodic memory” (Schwartz, 2011, p. 119). Episodic memories are the recall of events in our past, while the focus of prospective memories is of events in our future. In general, humans are fairly good at prospective memory if they have little else to do in the meantime. However, when there are competing tasks that also demand our attention, this type of memory rapidly declines. One explanation given for this phenomenon is that this form of memory draws on the central executive of working memory, and when this component of working memory is absorbed in other tasks, our ability to remember to do something else in the future is more likely to slip out of memory (Schwartz, 2011).

However, prospective memories are often divided into time-based prospective memories, such as having to remember to do something at a future time, or event-based prospective memories, such as having to remember to do something when a certain event occurs. When age-related declines are found, they are more likely to be time-based, rather than event-based, and in laboratory settings rather than in the real-world, where older adults can show comparable or slightly better prospective memory performance (Henry et al., 2004; Luo & Craik, 2008). This should not be surprising given the tendency of older adults to be more selective in where they place their physical, mental, and social energy. Having to remember a doctor’s appointment is of greater concern than remembering to hit the space-bar on a computer every time the word “tiger” is displayed, and outside the lab many more compensatory aids (e.g., post-it notes, calendars, phone alarms) are readily available.

Recall versus Recognition

Memory performance often depends on whether older adults are asked to simply recognize previously learned material or recall material on their own. Generally, for all humans, recognition tasks are easier because they require less cognitive energy. Older adults show roughly equivalent memory to young adults when assessed with a recognition task (Rhodes et al., 2008). However, in recall tasks, older adults show memory deficits in comparison to younger adults. While the effect is initially not that large, starting at age 40 adults begin to show regular age-graded declines in recall memory compared to younger adults (Schwartz, 2011).

The Age Advantage

Fewer age differences are observed when memory cues are available, such as for recognition memory tasks, or when individuals can draw upon acquired knowledge or experience. For example, older adults often perform as well if not better than young adults on tests of word knowledge or vocabulary. Expertise often comes with age, and research has pointed to areas where aging experts perform quite well. For example, older typists were found to compensate for age-related declines in speed by looking farther ahead at printed text (Salthouse, 1984). Compared to younger players, older chess experts focus on a smaller set of possible moves, leading to greater cognitive efficiency (Charness, 1981). Accrued knowledge of everyday tasks, such as grocery prices, can also help older adults make better decisions than young adults (Tentori et al., 2001).

New Research on Aging and Cognition

Can the brain be trained in order to build cognitive reserve to reduce the effects of normal aging? ACTIVE (Advanced Cognitive Training for Independent and Vital Elderly), a study conducted between 1999 and 2001 in which 2,802 individuals age 65 to 94, suggests that the answer is “yes.” These participants received 10 group training sessions and 4 follow up sessions to work on tasks of memory, reasoning, and speed of processing. These mental workouts improved cognitive functioning even 5 years later. Many of the participants believed that this improvement could be seen in everyday tasks as well (Willis et al, 2006). Learning new things, engaging in activities that are considered challenging, and being physically active at any age may build a reserve to minimize the effects of primary aging of the brain.