Search and selection processes in implicit and explicit word-stem completion performance in young, middle-aged, and older adults

Age differences in priming as a function of processing at encoding

It is unclear whether implicit memory (priming) is affected by aging. Some studies have reported no difference between young and older adults, while others have uncovered reliable reductions. An important factor that may explain these discrepancies is the manner of encoding. Processing requirements (perceptual/conceptual) have varied considerably between studies, yet processing abilities are not equally affected by aging. This study examined whether processing during encoding moderates age effects on priming. Young and older participants studied object-word pairs and made natural/manufactured (conceptual) and left/right rotation (perceptual) judgements in relation to the word or object. Objects served as targets on a subsequent continuous identification with recognition task to assess priming and recognition. Priming and recognition were greater in young than older adults for attended items, with a larger effect size in the conceptual than the perceptual condition. Findings suggest that age differences in priming may be a function of processing at encoding.

Age and processing effects on perceptual and conceptual priming

Explicit (declarative) memory declines with age, but age effects on implicit (nondeclarative) memory are debated. Some studies have reported null changes in implicit memory (e.g., priming in word-fragment completion, perceptual identification, category exemplar generation) with age, while others have uncovered declines. One factor that may account for these discrepancies is processing. Evidence suggests that conceptual and perceptual processes are not equally affected by ageing, yet processing requirements have varied greatly between studies. Processing may moderate age effects on priming, but no study has systematically examined this issue. This registered report presents an experiment to manipulate processing (conceptual / perceptual) during incidental encoding of words, prior to measures of perceptual (perceptual identification) and conceptual (category verification) priming. The perceptual and conceptual priming tasks were matched on all characteristics except processing, making them highly comparable. The four orthogonal conditions (perceptual encoding, perceptual test [PP]; conceptual encoding, perceptual test [CP]; perceptual encoding, conceptual test [PC]; conceptual encoding, conceptual test [CC]) were designed to clarify situations in which age effects on implicit memory emerge, which holds important practical and theoretical implications. Significant effects of Age, Test, and an Age × Processing interaction emerged. Priming was greater in young than older adults and on the perceptual than the conceptual test, but in contrast to the predictions, the age difference was only significant when prior encoding was perceptual (i.e., in the PP and CP conditions).

Age-Related Cognitive Effects of Videogame Playing Across the Adult Life span

OBJECTIVE

Previous studies found positive influences of videogame playing on cognition. However, the age-related and task-related effects of videogame experience across the adult life span are still unknown. The current study aimed to systematically investigate this question.

MATERIALS AND METHODS

The current study used the cross-sectional approach. A total of 166 participants (84 videogame players [VGPs], 82 nonvideogame players [NVGPs]) at the age of 18-80 in the present study were recruited, including 62 young adults aged from 18 to 34 (35 VGPs, 27 NVGPs), 55 middle-aged adults aged between 35 and 59 (24 VGPs, 31 NVGPs), and 49 older adults aged between 60 and 80 (25 VGPs, 24 NVGPs).^1,2 A series of neuropsychological tests from different cognitive domains, including processing speed, visuospatial, attention, memory, and executive function, were conducted on participants.

RESULTS

The age-related effects demonstrated that young and older adults benefited more from videogame experience than middle-aged adults. The task-related effects showed that VGPs benefited more from videogame experience in processing speed and visuospatial processing; next was executive function and attention, while no benefits in memory. The effect sizes suggested that the difference in extent between VGPs and NVGPs in processing speed and visuospatial processing is moderate, in attention and executive function is small, and in memory is negligible.

CONCLUSION

The current findings support the beneficial effects and transfer effects of videogame experience; however, the effects presented age-specific and task-specific characteristics. The results provide useful insights for future videogame intervention studies for healthy adults of different ages.

Spanish norms for completion of restricted length word stems

This study presents a normative database of Spanish restricted length word stems that provides useful information for the selection of stimuli in memory experiments with Word Stem Completion (WSC) tasks. The database includes indices relative to stems (total baseline completion, priming baseline completion, priming, number of completions, ratio between given and deleted letters, and syllabic structure), and indices relative to characteristics of the words used to obtain the stems (frequency, familiarity, number of meanings, length, number of syllables, arousal, and valence). A WSC task was performed by 515 participants to calculate priming and baseline indices. An Exploratory Factor Analysis showed that these indices are grouped in four factors: perceptual, lexical, emotional, and response competition. Stepwise regression analyses performed with these factors showed that the lexical, response competition, and perceptual factors predict priming baseline completion, while only the lexical factor predicts priming. The model that best explains the relationship between priming and priming baseline completion was a cubic model, and the optimum baseline values for achieving priming were between .31 and .36. These norms can be downloaded as Supplemental Materials for this article from https://nuvol.uv.es/owncloud/index.php/s/hpj9by1qbENdjfj .

Caffeine Enhances Memory Performance in Young Adults during Their Non-optimal Time of Day

Many college students struggle to perform well on exams in the early morning. Although students drink caffeinated beverages to feel more awake, it is unclear whether these actually improve performance. After consuming coffee (caffeinated or decaffeinated), college-age adults completed implicit and explicit memory tasks in the early morning and late afternoon (Experiment 1). During the morning, participants ingesting caffeine demonstrated a striking improvement in explicit memory, but not implicit memory. Caffeine did not alter memory performance in the afternoon. In Experiment 2, participants engaged in cardiovascular exercise in order to examine whether increases in physiological arousal similarly improved memory. Despite clear increases in physiological arousal, exercise did not improve memory performance compared to a stretching control condition. These results suggest that caffeine has a specific benefit for memory during students’ non-optimal time of day – early morning. These findings have real-world implications for students taking morning exams.

Age Effects in Implicit Memory: The Role of Response Competition Induced by Relative Word Frequency

BACKGROUND/STUDY CONTEXT

This study examined the effect of age and response competition on implicit memory performance.

METHODS

Younger and older adults studied high- and low-frequency words and took a word stem completion test that could be completed with multiple solutions. To manipulate response competition, the test list consisted of word stems that could be completed with target low-frequency words, as well as multiple other solutions with higher frequencies than the target (the high response competition condition) and word stems that could be completed with target high-frequency words, as well as multiple other solutions with lower frequencies than the target (the low response competition condition).

RESULTS

Relative to younger adults, older adults showed reduced levels of priming only under conditions of high response competition (low-frequency targets with high-frequency competitors).

CONCLUSION

In support of a response competition mechanism, older adults were more likely to complete stems with nonstudied high-frequency solutions than were younger adults. Results demonstrate that older adults have reduced priming compared with younger adults under some conditions of high response competition.

Priming in word stem completion tasks: comparison with previous results in word fragment completion tasks

This study investigates priming in an implicit word stem completion (WSC) task by analyzing the effect of linguistic stimuli characteristics on said task. A total of 305 participants performed a WSC task in two phases (study and test). The test phase included 63 unique-solution stems and 63 multiple-solution stems. Analysis revealed that priming (mean = 0.22) was stronger in the case of multiple-solution stems, indicating that they were not a homogeneous group of stimuli. Thus, further analyses were performed only for the data of the unique-solution stems. Correlations between priming and familiarity, frequency of use, and baseline completion were significant. The less familiar words, which were less frequent, had higher priming values. At the same time, the stems with lower baseline completion generated more priming. A regression analysis showed that baseline completion was the only significant predictor of priming, suggesting that the previous processing of the stimuli had a greater impact on the stimuli with low baseline performance. At the same time, baseline completion showed significant positive correlations with familiarity and frequency of use, and a negative correlation with length. When baseline completion was the dependent variable in the regression analysis, the significant variables in the regression were familiarity and length. These results were compared with those obtained in a study using word fragment completion (WFC) by Soler et al. (2009), in which the same words and procedure were employed. Analysis showed that the variables that correlated with priming were the same as in the WSC task, and that completion baseline was the variable that showed the greatest predictive power of priming. This coincidence of results obtained with WFC and WSC tasks highlights the importance of controlling the characteristics of the stimuli used when exploring the nature of priming.

Long-Term Recency in Anterograde Amnesia

Amnesia is usually described as an impairment of a long-term memory (LTM) despite an intact short-term memory (STM). The intact recency effect in amnesia had supported this view. Although dual-store models of memory have been challenged by single-store models based on interference theory, this had relatively little influence on our understanding and treatment of amnesia, perhaps because the debate has centred on experiments in the neurologically intact population. Here we tested a key prediction of single-store models for free recall in amnesia: that people with amnesia will exhibit a memory advantage for the most recent items even when all items are stored in and retrieved from LTM, an effect called long-term recency. People with amnesia and matched controls studied, and then free-recalled, word lists with a distractor task following each word, including the last (continual distractor task, CDFR). This condition was compared to an Immediate Free Recall (IFR, no distractors) and a Delayed Free Recall (DFR, end-of-list distractor only) condition. People with amnesia demonstrated the full long-term recency pattern: the recency effect was attenuated in DFR and returned in CDFR. The advantage of recency over midlist items in CDFR was comparable to that of controls, confirming a key prediction of single-store models. Memory deficits appeared only after the first word recalled in each list, suggesting the impairment in amnesia may emerge only as the participant’s recall sequence develops, perhaps due to increased susceptibility to output interference. Our findings suggest that interference mechanisms are preserved in amnesia despite the overall impairment to LTM, and challenge strict dual-store models of memory and their dominance in explaining amnesia. We discuss the implication of our findings for rehabilitation.

Priming effects from young-old to very old age on a word-stem completion task: minimizing explicit contamination

We investigated the size of repetition priming effects from young-old to very old age using a newly developed Word-Stem Completion (WSC) task. Retrospectively, we examined the role of explicit, intentional retrieval strategies in priming. We constructed our task by taking factors into account that were known to complicate the measurement of significant and valid priming effects. Within our sample of 170 cognitively healthy elderly persons of 55-94 years old, we found no effects on priming of age, gender, education, intelligence, cognitive status, memory complaints, or depressive symptoms. Participants that subsequent to task administration reported awareness of the study-test relationship obtained higher priming scores. However, analysis of stem-completion times showed that explicit contamination during the task was unlikely. The results suggest that WSC priming is age-invariant up to very old age. This task with increased validity might contribute to the differentiation with Alzheimer's disease by improving specificity of assessment.

The sound of mute vowels in auditory word-stem completion

Some studies have argued that orthography can influence speakers when they perform oral language tasks. Words containing a mute vowel provide well-suited stimuli to investigate this phenomenon because mute vowels, such as the second <e> in <vegetable>, are present orthographically but absent phonetically. Using an auditory word-stem completion task, we tested whether subjects were influenced by the presence of mute vowels. We ran experiments in two languages which contain numerous mute-vowel words: Tigrinya, which uses a syllabic/moraic writing system, and French, which uses an alphabetic writing system. We argue that Tigrinya and French speakers based their completion on the sound form of words, rather than the written one. We suggest that the presence of mute vowels at the underlying phonological level, rather than their orthographic representation, influences speakers in the word-stem completion task. Some effects previously attributed to orthography may instead be attributable to underlying phonological representations.

Examining the response competition hypothesis of age effects in implicit memory

Age reductions in priming have been explained by differences in processing demands across implicit memory tests. According to one hypothesis, older adults show reduced priming relative to younger adults on implicit tests that require production of a response because these tests typically allow for response competition. In contrast, older adults do not show reductions in priming on identification tests that contain little response competition. The following experiments tested the specific role of response competition in mediating age effects in implicit memory. In Experiment 1, younger and older adults studied a list of words and were then given an implicit test of word stem completion. They studied a second list of words and were given an implicit test of general knowledge. Each implicit test contained items with unique solutions (the low response competition condition) and items with multiple solutions (the high response competition condition). In Experiment 2, younger and older adults were given explicit versions of the word stem completion and the general knowledge tests. Results showed an effect of age on explicit memory (Experiment 2), but no effect of age or response competition on priming (Experiment 1). Results are inconsistent with the theory that response competition leads to age effects on production tests of implicit memory.

Automatic memory processes in normal ageing and Alzheimer's disease

This study examined the contribution of automatic and controlled uses of memory to stem completion in young, middle-aged and older adults, and compared these data with a study involving patients with Alzheimer's disease (AD) who performed the same task (Hudson and Robertson, 2007). In an inclusion task participants aimed to complete three-letter word stems with a previously studied word, in an exclusion task the aim was to avoid using studied words to complete stems. Performances under inclusion and exclusion conditions were contrasted to obtain estimates of controlled and automatic memory processes using process-dissociation calculations (Jacoby, 1991). An age-related decline, evident from middle age was observed for the estimate of controlled processing, whereas the estimate of automatic processing remained invariant across the age groups. This pattern stands in contrast to what is observed in AD, where both controlled and automatic processes have been shown to be impaired. Therefore, the impairment in memory processing on stem completion that is found in AD is qualitatively different from that observed in normal ageing.

Repetition priming without identification of the primes: evidence for a component process view of priming

The aim of the present study was to examine whether priming can occur due to recent perceptual processing of the same stimulus with minimal influence from conceptual process and also to investigate its underlying neural mechanisms using fMRI. Words were presented in mirror orientation in a word identification priming task. The presentation durations of the primes were titrated individually so that each participant could only identify approximately half of the primes, while the remainder disappeared before participants could identify the meaning of the word. A substantial behavioral priming effect was found when these unidentified primes were repeated later, suggesting that recent exposure to the perceptual processes without accessing the meaning is sufficient to prime later identical processes of the same repeated stimuli. Imaging data showed significant repetition suppression in several brain regions mediating perceptual, but not semantic or conceptual, processes. Together, our findings are consistent with the general predictions of transfer appropriate processing (TAP) and the component process view of priming, positing that priming is a function of more efficient cognitive processes that are repeated from study to test, and this increased efficiency is reflected in repetition suppression effects evident on fMRI.

Does priming with awareness reflect explicit contamination? An approach with a response-time measure in word-stem completion

The present experiment investigates the involvement of awareness in functional dissociations between explicit and implicit tests. In the explicit condition, participants attempted to recall lexically or semantically studied words using word stems. In the implicit condition, they were instructed to complete each stem with the first word which came to mind. Subjective awareness was subsequently measured on an item-by-item basis. As voluntary retrieval strategies are known to be time consuming, the time taken to complete each stem was recorded. In the explicit task, semantically studied words were associated with higher levels of recall and faster response times than lexically studied words. By contrast, in the implicit task, these effects failed to reach significance, although deep encoding made the contents of memory more accessible to awareness. As expected, performance was slower in the explicit than in the implicit task, but in the latter condition, times to produce old words with and without awareness were comparable, and both of these responses were produced more quickly than control words. This finding suggests that although participants may become aware in implicit paradigms, they do not adopt voluntary retrieval strategies.

Abstractionist versus exemplar-based theories of visual word priming: a subsystems resolution

Three experiments addressed abstractionist versus exemplar-based theories of the visual representations underlying word priming. Participants first read centrally presented whole words (each displayed in all lowercase or in all uppercase letters), and then they completed laterally presented word stems (each displayed in all lowercase or in all uppercase letters). Word stem completion priming was letter-case specific (greater for same-case primed items than for different-case primed items) when stems were presented directly to the right cerebral hemisphere but not when stems were presented directly to the left cerebral hemisphere. This interaction was not influenced by the typicality of the test stems, but it was observed only for stems composed of letters with visually dissimilar lowercase and uppercase structures (e.g., bea/BEA) and not for stems composed of letters with visually similar lowercase and uppercase structures (e.g., sco/SCO). In contrast, cued recall was letter-case specific when similar-case or dissimilar-case stems were presented directly to the right hemisphere. Results do not support strongly abstractionist or exemplar-based theories. Instead, they suggest a resolution to these differing perspectives: Relatively independent neural subsystems operate in parallel to underlie abstract-category and specific-exemplar priming of word forms.

Age differences in implicit memory: conceptual, perceptual, or methodological?

The authors examined age differences in conceptual and perceptual implicit memory via word-fragment completion, word-stem completion, category exemplar generation, picture-fragment identification, and picture naming. Young, middle-aged, and older participants (N = 60) named pictures and words at study. Limited test exposure minimized explicit memory contamination, yielding no reliable age differences and equivalent cross-format effects. In contrast, explicit memory and neuropsychological measures produced significant age differences. In a follow-up experiment, 24 young adults were informed a priori about implicit testing. Their priming was equivalent to the main experiment, showing that test trial time restrictions limit explicit memory strategies. The authors concluded that most implicit memory processes remain stable across adulthood and suggest that explicit contamination be rigorously monitored in aging studies.

A Quantitative Model-Based Approach to Examining Aging Effects on Information-Integration Category Learning

Information-integration category learning was examined in older and younger adults. Accuracy results indicated that older participants learned less well than younger participants in both linear and nonlinear conditions. Model-based analyses indicated that both groups in the linear condition tended to use information integration but that later in training younger participants were more likely to do so. In contrast, the 2 groups in the nonlinear condition were equally likely to use information integration. Further analysis indicated that younger adults were more accurate than older adults when an information-integration approach was adopted, whereas fewer age-related differences were observed when a rule-based approach was used, suggesting that age can have a negative impact on information-integration category learning processes but less impact on rule-based learning.

An examination of daily activities and their scripts across the adult lifespan

In two normative studies, we examined daily scripted activities from the perspective that scripts are frequency-based knowledge structures. In Study 1 individuals recorded their daily activities for 7 consecutive days. Fifteen activities that were reported with low, moderate, and high frequency were selected for Study 2, in which individuals generated a script for each activity. The 18 most frequently generated events from each script are reported, along with their centrality and distinctiveness rankings and the number of individuals reporting each event. Overall, the mean number of events generated increased with increasing script frequency, suggesting that script representations are subject to frequency effects. Also, we found a high level of consistency across the three age groups in the events generated in each script and in their corresponding rankings of centrality and distinctiveness. Finally, we found no evidence of age or gender bias in the frequency or recency of engaging in each of the scripted activities.

More on magnitude of priming in implicit memory tasks

The effects of word frequency, length of the word, and type of word fragment in a fragment-completion test were investigated with 57 undergraduate students, 19-22 years. Priming with better performance on studied than on nonstudied words in this task was greater for low frequency words than for high frequency words and greater for fragments without the first letter than for fragments with the first letter. It was inferred that characteristics of fragments should be considered in any implicit memory task when the magnitude of priming is of interest. In general, word fragment-completion processes appear to be based on sources of information available in visual identification tasks.