Effects of depth-of-processing and ageing on word-stem and word-fragment implicit memory tasks: Test of the lexical-processing hypothesis

The joint effects of depth-of-processing and age on repetition priming in implicit memory tests of word-fragment completion (WFC) and word-stem completion (WSC) were investigated. The experiment consisted of three study tasks (perceptual, lexical, and semantic) and four memory conditions: implicit (WSC and WFC) and explicit (WS cued recall and WF cued recall). In the WSC condition, semantic and lexical study processing produced equal priming, both superior to the perceptual study processing, whereas the WFC test showed equal priming for these three study conditions. This finding provides clear evidence, consistent with the lexical-processing hypothesis, that depth-of-processing in WSC priming reflects a lexical rather than a semantic process. It also provides support for the view that WSC and WFC involve different processes. However, there was no evidence of an age effect on either of these two implicit tasks. The data also revealed an overall significant effect of age and depth-of-processing, and an interaction between these variables on explicit cued recall tasks, indicating that older adults benefited less than younger ones from a deep encoding condition.     

Effects of attentional load and ageing on word-stem and word-fragment implicit memory tasks

The joint effects of reduced attention and age on repetition priming in implicit memory tests of word-fragment completion (WFC) and word-stem completion (WSC) were investigated. An attention load during the study phase reduced the extent of repetition priming in the WSC condition but not in WFC. This finding provides support for the view that WSC and WFC involve different processes. However, there was no evidence of an age effect on either of these two types of implicit tasks. The data also revealed an overall significant effect of age and reduced attention on explicit cued recall tasks.     

Manipulation of familiarity reveals a necessary lexical component of the word-stem completion priming effect

These experiments were motivated by the idea that many types of nondeclarative memory are by-products arising from the plasticity that is inherent in much of the nervous system. We hypothesized that two types of repetition priming, word-stem completion (WSC) priming and perceptual identification (PI) priming, rely on different mechanisms because the WSC task and the PI task engage different cognitive and brain processes. We tested this hypothesis by manipulating word familiarity. The results, impaired WSC priming but intact PI priming with unfamiliar words, indicate that WSC priming relies primarily on a modification mechanism, whereas PI priming relies primarily on an acquisition mechanism. Our conclusions are consistent with component processes theories of nondeclarative memory.     

Contribution of the priming paradigm to the understanding of the conceptual developmental shift from 5 to 9 years of age

We conducted three experiments to study the role of instrumental (e.g. knife–bread) and categorical (e.g. cake–bread) relations in the development of conceptual organization with a priming paradigm, by varying the nature of the task (naming – Experiment 1 – or categorical decision – Experiments 2 and 3). The participants were 5‐, 7‐ and 9‐year‐old children and adults. The results showed that on both types of task, adults and 9‐year‐old children presented instrumental and categorical priming effects, whereas 5‐year‐old children presented mainly instrumental priming effects, with categorical effects remaining marginal. Moreover, the magnitude of the instrumental priming effects decreased with age. Finally, the priming effects observed for 7‐year‐old children depended on the task, especially for the categorical effects. The theoretical implications of these results for our understanding of conceptual reorganization from 5 to 9 years of age are discussed.     

Aging affects word-stem completion and recognition but not category generation

In this study, we investigated the effect of aging on two implicit memory tasks, word-stem completion and category generation, and on explicit recognition. We compared the performance of young and older adults on these implicit memory tasks with those of explicit recognition. We expected better performance of young than older adults in the explicit memory task and similar priming in both implicit memory tasks. The results showed that young adults performed better than older adults in the recognition task. Moreover, both age groups showed priming in the implicit memory tasks, although priming was greater in young adults compared to older adults in the word-stem completion memory task, whereas both age groups showed similar levels of priming in the category generation task. The present results showed dissociations as a function of age not only between the explicit and the implicit tasks but also between the implicit tasks.     

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

In the present investigation, we sought to (1) replicate previous reports of impaired word-stem completion (WSC) priming and cued recall performance in older adults, (2) gain a better understanding of the differential roles of search and selection processes in implicit and explicit WSC, and (3) determine the particular aspects of WSC performance that are influenced by age. Experiment 1 demonstrated that older adults primed and recalled fewer items on a WSC task than middle-aged adults did, who in turn primed and recalled fewer items than young adults did. A series of item analyses indicated that choice of a stem completion is influenced by two independent sources of information: the familiarity of the completion reflected by word frequency and the cue-specific match between the stem and the completion word based on the common pronunciation of the stem. Experiment 2 demonstrated that older adults utilized cue-specific matching to the same degree as young and middle-aged adults. However, the impact of target familiarity changed across the lifespan. Older adults produced and recalled high-frequency targets as well as young adults but produced and recalled fewer low-frequency targets than did young participants. The results are consistent with the view that older adults rely on familiarity to a greater degree than do young adults.     

Decreased parahippocampal activity in associative priming: evidence from an event-related fMRI study

In recent years, there has been intense debate on the neural basis of associative priming, particularly on the role of the medial temporal lobe (MTL) in retrieving associative information without awareness. In this study, event-related fMRI was used while healthy subjects performed a perceptual identification task on briefly presented unrelated word pairs and an associative recognition memory task. Contamination of priming by explicit memory was successfully controlled, as associative priming and explicit memory were dissociated on the behavioral level. The fMRI results showed a functional dissociation within the MTL with respect to associative priming effects. The right parahippocampal cortex, but not the hippocampus, showed decreased activation for old vs. new pairs and old vs. recombined pairs (associative priming). The bilateral hippocampus and the right parahippocampal cortex were involved in explicit associative memory. These data provide evidence that subregions of the MTL participate in associative priming even when explicit involvement was controlled. Thus, different regions within the MTL play distinct roles in explicit and implicit associative memory.     

Implicit memory for novel conceptual associations in amnesia

In two experiments, we evaluated the status of implicit memory for novel associations in amnesia. Experiment 1 assessed priming in a category exemplar generation task in which contextual information associated with a target could increase the likelihood of target generation. Control participants, but not amnesic patients, showed associative priming. Amnesics’ impairment was not due to the use of explicit memory by control subjects but reflected a genuine impairment in implicit memory for novel conceptual associations. Experiment 2 assessed priming in a relatedness judgment task, in which associative priming was manifest as longer latencies for old than for recombined pairs of unrelated words. Amnesic patients showed intact associative priming in this task. We discuss differences in the status of implicit memory for novel conceptual associations in amnesia, with reference to the nature of the representation that supports priming in the two tasks and the type of processing that is required at test.     

内隐与外显记忆的编码与提取非对称性关系

实验采用“学习-测验”范式, 考察在编码或提取中分别附加的干扰任务对内隐测验或外显测验中获得的ERP新旧效应产生的影响。结果表明, 在内隐测验中, 编码干扰对随后测验中的ERP新旧效应没有产生影响, 而提取干扰却改变了300~500ms新旧效应的脑区位置, 破坏了500~700ms新旧效应; 与之相反, 在外显测验中, 编码干扰破坏了500~700ms新旧效应, 而提取干扰对这一效应没有产生影响, 即编码与提取干扰对内隐或外显测验中的ERP新旧效应都产生了非对称性的影响, 但又存在着差异, 从而为两种记忆在编码与提取加工的关系上存在的分离现象提供了神经生理方面的证据。     

Aging and the Deletion Function of Inhibition

The present study was adapted from the sentence completion task of Hartman and Hasher (1991). We addressed the question raised by Burke (1997): are the age-related differences in priming effects found in that task better explained by deficits in explicit memory or by inefficient inhibitory mechanisms? In the study phase, older and younger adults read high cloze sentences ending with an expected or an unexpected final word. In the second phase, participants were asked to complete sentence frames with either the final word presented during the study phase (inclusion condition) or with another, new word (exclusion condition). The third phase was an indirect memory test of perceptual identification. Finally, we compared explicit memory for recalled and inhibited words in a recognition test. In perceptual identification by older adults, priming was equivalent for recalled and inhibited words, whereas in younger adults priming was higher for recalled than for inhibited words. In the explicit memory test, recognition scores were lower for inhibited words in both age groups. These results are consistent with the view of Hasher and Zacks (1988), who assume an age-related decline in the ability to suppress no-longer-relevant information     

Temporal processing characteristics of the Ponzo illusion

Many visual illusions result from assumptions of our visual system that are based on its long-term adaptation to our visual environment. Thus, visual illusions provide the opportunity to identify and learn about these fundamental assumptions. In this paper, we investigate the Ponzo illusion. Although many previous studies researched visual processing of the Ponzo illusion, only very few considered temporal processing aspects. However, it is well known that our visual percept is modulated by temporal factors. First, we used the Ponzo illusion as prime in a response priming task to test whether it modulates subsequent responses to the longer (or shorter) of two target bars. Second, we used the same stimuli in a perceptual task to test whether the Ponzo illusion is effective for very short presentation times (12 ms). We observed considerable priming effects that were of similar magnitude as those of a control condition. Moreover, the variations in the priming effects as a function of prime-target stimulus-onset asynchrony were very similar to that of the control condition. However, when analyzing priming effects as a function of participants’ response speed, effects for the Ponzo illusion increased in slower responses. We conclude that although the illusion is established rapidly within the visual system, the full integration of context information is based on more time-consuming and later visual processing.     

What happens to our representation of identity as familiar faces age? Evidence from priming and identity aftereffects

Matching identity in images of unfamiliar faces is error prone, but we can easily recognize highly variable images of familiar faces – even images taken decades apart. Recent theoretical development based on computational modelling can account for how we recognize extremely variable instances of the same identity. We provide complementary behavioural data by examining older adults’ representation of older celebrities who were also famous when young. In Experiment 1, participants completed a long-lag repetition priming task in which primes and test stimuli were the same age or different ages. In Experiment 2, participants completed an identity after effects task in which the adapting stimulus was an older or young photograph of one celebrity and the test stimulus was a morph between the adapting identity and a different celebrity; the adapting stimulus was the same age as the test stimulus on some trials (e.g., both old) or a different age (e.g., adapter young, test stimulus old). The magnitude of priming and identity after effects were not influenced by whether the prime and adapting stimulus were the same age or different age as the test face. Collectively, our findings suggest that humans have one common mental representation for a familiar face (e.g., Paul McCartney) that incorporates visual changes across decades, rather than multiple age-specific representations. These findings make novel predictions for state-of-the-art algorithms (e.g., Deep Convolutional Neural Networks).     

The effects of attention on perceptual implicit memory

Reports on the effects of dividing attention at study on subsequent perceptual priming suggest that perceptual priming is generally unaffected by attentional manipulations as long as word identity is processed. We tested this hypothesis in three experiments by using the implicit word fragment completion and word stem completion tasks. Division of attention was instantiated with the Stroop task in order to ensure the processing of word identity even when the participant's attention was directed to a stimulus attribute other than the word itself. Under these conditions, we found that even though perceptual priming was significant, it was significantly reduced in magnitude. A stem cued recall test in Experiment 2 confirmed a more deleterious effect of divided attention on explicit memory. Taken together, our findings delineate the relative contributions of perceptual analysis and attentional processes in mediating perceptual priming on two ubiquitously used tasks of word fragment completion and word stem completion.     

In what sense is implicit memory "episodic"? The effect of reinstating environmental context

We consider three aspects of the term episodic. Previous literature shows implicit memory does not make conscious autobiographical reference but does code an item's intrinsic context (e.g., perceptual detail). Here, we consider extrinsic context--namely, that not directly processed as part of item identification and not overtly relevant to the task. Study-test mismatch in environmental context (outdoors vs. indoors) reduced memory in an explicit stem-cued recall task but had no effect on repetition priming in an implicit stem completion task. This was true even for very low frequency words. We support the view that implicit memory reflects traces within perceptual (or semantic) knowledge-based systems that are instance specific but do not code the full spatiotemporal context information necessary to support conscious recollection. We also interpret our results as consistent with differences in environmental context specificity between free recall and recognition.     

Effects of hearing words, imaging hearing words, and reading on auditory implicit and explicit memory tests

In four experiments, we examined the degree to which imaging written words as spoken by a familiar talker differs from direct perception (hearing words spoken by that talker) and reading words (without imagery) on implicit and explicit tests. Subjects first performed a surface encoding task on spoken, imagined as spoken, or visually presented words, and then were given either an implicit test (perceptual identification or stem completion) or an explicit test (recognition or cued recall) involving auditorily presented words. Auditory presentation at study produced larger priming effects than did imaging or reading. Imaging and reading yielded priming effects of similar magnitude, whereas imaging produced lower performance than reading on the explicit test of cued recall. Voice changes between study and test weakened priming on the implicit tests, but did not affect performance on the explicit tests. Imagined voice changes affected priming only in the implicit task of stem completion. These findings show that the sensitivity of a memory test to perceptual information, either directly perceived or imagined, is an important dimension for dissociating incidental (implicit) and intentional (explicit) retrieval processes.     

Automatically activated facets of ageism: Masked evaluative priming allows for a differentiation of age‐related prejudice

This study investigated the automatic activation of ageism by using a go/no‐go version of the masked evaluative priming task. Pictures of younger persons, of older persons in everyday contexts, and of older persons depicting age‐related conditions of decline were used as masked primes that preceded positive and negative target adjectives conveying either other‐relevant valence (e.g., just and mean) or possessor‐relevant valence (e.g., serene and lonely). The evaluative priming effect (denoting relative negativity of old‐everyday primes in comparison with younger primes) was significant, as hypothesized, only for possessor‐relevant targets. It was not moderated by explicit ageism. A second priming index (denoting relative negativity of old‐decline primes in comparison with old‐everyday primes) predicted, however, explicit ageism. Again, this result was, as expected, constrained to the index based on possessor‐relevant targets. This study provides further evidence that prejudice in terms of automatic evaluations of social stimuli can be more fine grained beyond a mere one‐dimensional positive–negative differentiation. Copyright © 2012 John Wiley & Sons, Ltd.     

Investigating semantic memory impairments: The contribution of semantic priming

Abstract

The semantic priming task is a valuable tool in the investigation of semantic memory impairments in patients with acquired disorders of language. This is because priming performance reflects automatic or implicit access to semantic information, unlike most other tests of semantic knowledge, which rely on explicit, voluntary access. Priming results are important for two main reasons: First, normal priming results may be observed in patients who perform poorly on other semantic memory tests, enabling us to distinguish between loss of, or damage to, information in semantic memory, and voluntary access to that information. Second, we can investigate the detailed pattern of loss and preservation of different types of semantic information, by charting the priming effects for different kinds of words, and different kinds of semantic relations between primes and targets.

We discuss the use of the priming task in this context, and address some of the theoretical and methodological criticisms that have been raised in connection with use of the priming task to address these issues. We then describe two recent studies in which we have employed semantic priming tasks, along with other more traditional methods, to investigate specific questions about the semantic memory deficits of three patients.     

What colour is the car? Implicit memory for colour information in children

Three experiments were conducted to examine age-related differences in colour memory. In Experiment 1, preschool age and elementary school age children were given a conceptual test of implicit colour memory (a colour-choice task). They were presented with the names or achromatic versions of previously studied coloured line drawings and asked to select an appropriate colour. Significant priming could be demonstrated: The children chose the previously seen colours more often than was expected by chance. Equivalent priming was found for both versions (pictorial and verbal) suggesting that colour priming may be conceptually mediated. Moreover, colour priming proved to be age invariant. Experiment 2 replicated and extended this finding by using a wider age group (preschool, elementary school, and young adults) and by giving a perceptual implicit task (picture identification) in addition to a verbal colour-choice task. Colour did not affect priming in the perceptual task. Whereas priming showed no developmental change, agerelated improvements were observed on an explicit colour memory task that differed only in the test instructions from the implicit colour-choice task (Experiments 2 and 3). Taken together, the results suggest that implicit colour memory may be mediated by conceptual processes that are age invariant.     

Opposing effects of age and reading ability on pseudoword priming

Repetition priming refers to the facilitation of stimulus processing due to prior processing of the same or similar stimulus, and is one of the most primitive ways in which experience and practice can affect performance. Previous studies have produced contradictory results regarding the stability of repetition priming across development. Drawing on models of word priming that suggest decreased priming with increased reading ability, the present experiment investigated the possibility that null effects of age in priming are due to opposing effects of age and reading ability on priming magnitude. Forty-eight participants between 7 and 22 years old read aloud primed and unprimed pseudowords, after completing a reading ability assessment. In line with predictions, the magnitude of priming for pseudowords increased with increased age when reading ability was controlled, and decreased with increased reading ability when age was controlled. Moreover, neither the age nor ability effect was significant when tested without the other. Results were not influenced by explicit memory for primed pseudowords. Thus, the present experiment provides evidence for developmental increases in word priming, as well as a potential explanation for the lack of developmental effects in previous studies.