The spacing effect depends on an encoding deficit, retrieval, and time in working memory: evidence from once-presented words

The spacing effect in list learning occurs because identical massed items suffer encoding deficits and because spaced items benefit from retrieval and increased time in working memory. Requiring the retrieval of identical items produced a spacing effect for recall and recognition, both for intentional and incidental learning. Not requiring retrieval produced spacing only for intentional learning because intentional learning encourages retrieval. Once-presented words provided baselines for these effects. Next, massed and spaced word pairs were judged for matches on their first three letters, forcing retrieval. The words were not identical, so there was no encoding deficit. Retrieval could and did cause spacing only for the first word of each pair; time in working memory, only for the second.     

Associative priming in word fragment completion: a dissociation between explicit and implicit retrieval processes

Three experiments investigated associative priming in word fragment completion. In associative priming, the study word that acts as a prime is semantically related in some way to the response word that the subject must produce or respond to at test. For example, a prime might be semantically related to the solution to its paired word fragment (e.g. study "VANILLA", solve fragment "-H-C--A-E" at test, solution is "CHOCOLATE"). Associative priming therefore differs from both repetition and conceptual priming, in which the studied primes are themselves the words that must be produced or responded to at test. In Experiment 1, associative primes were found to influence word fragment completion performance on an explicit test, but not on an implicit test. Experiment 2 demonstrated that the effects of associative primes on explicitly instructed fragment completion cannot be attributed to the specific information about cue-prime relationships that is included in the explicit instructions. Experiment 3 demonstrated that a manipulation of modality, a variable known to disrupt implicit retrieval processes, disrupts repetition priming on an explicit test, but not associative priming. The results of these three experiments suggest that whereas repetition primes are retrieved from memory by both explicit and implicit retrieval processes, associative primes are retrieved by only explicit processes. These data suggest that implicit retrieval processes are cue-dependent processes which automatically retrieve memory information that provides a good match to retrieval cues. Explicit retrieval processes are cue-independent, functioning as an intentional retrieval set to access particular categories or types of memory information.     

Brain regions supporting intentional and incidental memory: a PET study

Regional brain activity associated with intentional and incidental memory retrieval was studied with PET. Previously studied and new words were presented in either an intentional or an incidental memory task. Type of task was crossed with an encoding manipulation ('deep' vs 'shallow') which varied the probability that studied items would be remembered. In both tasks, deeply encoded items were associated with greater activation in the left hippocampus than were items that had received shallow encoding, suggesting that the involvement of the hippocampus in memory retrieval is independent of whether remembering is intentional or incidental. Right prefrontal and bilateral parietal cortex were more activated during the international task than during the incidental task, irrespective of encoding condition. Thus, these regions play a more extensive role in memory retrieval when remembering is intentional.     

Manipulation of attention at study affects an explicit but not an implicit test of memory

We investigated the impact of attention during encoding on later retrieval. During study, participants read some words aloud (ignoring the print color) and named the print color of other words aloud (ignoring the word). Then one of two memory tests was administered. The explicit test--recognition--required conscious recollection of whether a word was studied. Previously read words were recognized more accurately than were previously color named words. This contrasted sharply with performance on the implicit test--repetition priming in lexical decision. Here, words that were color named during study showed priming equivalent to words that were read during study; both were responded to faster than unstudied words. Thus, an attentional manipulation during study had a strong effect on an explicit test of memory, but almost no effect on an implicit test. Focal attention during study is crucial for remembering consciously but not necessarily for remembering without awareness.     

Failure to find the picture superiority effect in implicit conceptual memory tests.

According to the transfer appropriate processing framework (H. L. Roediger, M. S. Weldon, & B. A. Challis, 1989), if pictures engage more conceptual processing than words, then they should produce more priming on implicit conceptual tests. Experiments 1 and 2 did not find any significant advantage of pictures on the implicit category production or word association tests. When these tests were given as explicit cued-recall tests in Experiment 3, pictures were recalled better than words, producing a dissociation and indicating that the materials were sensitive to differences in picture and word processing. In Experiments 4 and 5, the implicit tests showed level-of-processing effects indicating that they were sensitive to differences in conceptual processing. Therefore, it is hypothesized that (a) conceptual processing plays a minor role, if any, in superior picture recall and that visual distinctiveness is a more important factor; and (b) distinctiveness is more important in intentional than incidental retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit false memory in the DRM paradigm: Effects of amnesia, encoding instructions, and encoding duration.

Recent studies with the Deese/Roediger–McDermott (Deese 1959; Roediger & McDermott, 1995) paradigm have revealed that amnesic patients do not only show impaired veridical memory, but also diminished false memory for semantically related lure words. Due to the typically used explicit retrieval instructions, however, this finding may reflect problems at encoding, at recollection, or both. Therefore, the present experiments examined implicit as well as explicit false memory in patients suffering from Korsakoff’s syndrome and controls. In Experiment 1, encoding instructions either focused on remembering individual list words, or on discovering semantic relationships among the words. In Experiment 2, different presentation durations were used. Results emphasize the distinction between automatic and intentional retrieval: Korsakoff patients’ veridical and false memory scores were diminished when explicit recollection was required, but not when memory was tested implicitly. Encoding manipulations only significantly affected veridical memory: Priming was reduced with thematic encoding, and explicit retrieval was facilitated when given more study time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The memory enhancement effect of emotion is absent in conceptual implicit memory.

Memory for emotional stimuli is superior to memory for neutral stimuli. This study investigated whether this memory advantage is present in implicit memory. Memory was tested with a test of explicit memory (associate cued recall) and a test of conceptual implicit memory (free association) identical in all respects apart from the retrieval instructions. After studying emotional and neutral paired associates, participants saw the first member of the pair, the cue; in the test of explicit memory participants were instructed to recall the associate; in the test of implicit memory participants were instructed to generate the first word coming to mind associated to the word. Depth of study processing dissociated performance in the tests, confirming that the free-association test was not contaminated by an intentional retrieval strategy. Emotional pairs were better recalled than neutral pairs in the test of explicit memory but not in the equivalent test of implicit memory. The absence of an emotion effect in implicit memory implies that emotional material does not have a privileged global mnemonic status; intentional retrieval is necessary for observing the emotion-related memory advantage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of generation on indirect measures of memory.

Subjects either read words (CHIMP) or generated words ("a small ape—C') during the study phase of three experiments. The effects of these encoding tasks on performance in two indirect, priming tests—word completion and word identification—were observed. The word completion test is a version of word stem completion in which subjects are shown the initial four letters of a five-letter word (e.g., CHIM_: CHIMP, CHIME) and are asked to add one letter to produce the first word that comes to mind. In word identification, subjects are shown a word briefly and are asked to identify it. Systematic comparisons of the two tests within single experiments showed that generation, either to semantic cues or to orthographic cues, had different effects on performance in the two tests: Word identification performance was lower for words generated rather than read, whereas word completion performance for words generated was indistinguishable from performance for words read. These results suggest that performance in different indirect tests depends on the processing of different types of information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in implicit and explicit memory: Time course and encoding effects.

Young and older adults were tested at three delays on word-stem completion or cued recall following semantic or structural word judgments. Identical three-letter stems were present at retrieval for both implicit (completion) and explicit (cued recall) tasks; only the intention to recall list words differed. The young adults outperformed the older adults on both implicit and explicit task at all test delays. Under some conditions, the older but not the young adults performed more poorly on cued recall than on stem completion, suggesting a possible failure to use implicitly available information to support explicit remembering. These results suggest that some forms of implicit memory decline with normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired Implicit Memory for Gist Information in Amnesia.

In 2 experiments using a converging associates paradigm, the authors evaluated implicit memory for gist information in amnesic patients. In Experiment 1, participants saw multiple sets of associates, each converging on a nonpresented theme word, and were then tested using an implicit word stem completion test and an explicit cued recall test. Amnesic patients showed intact implicit and impaired explicit memory for studied words, but memory for nonpresented lures was impaired, regardless of retrieval instructions. To evaluate whether impaired implicit memory for lures was due to accelerated forgetting of gist information, short study lists were used in Experiment 2, each consisting of a single set of associates. Amnesics' implicit memory for lures was again impaired. These results point to an inability to encode robust gist representations as the cause of impaired gist memory in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Building episodic connections: Changes in episodic priming with age and dementia.

Previous studies of associative encoding that used explicit retrieval tasks have shown both age- and dementia of the Alzheimer type (DAT)-related declines, but such results may be biased by group differences in explicit retrieval. In the present experiment, the authors assessed implicit associative encoding for 25 younger adults (ages 18–25), 73 healthy older adults (ages 59–91), and 65 adults with DAT (ages 59–91) during a speeded word-naming task using an episodic priming measure. Episodic priming refers to the facilitation in responding to a target word after repetition of both words in a prime–target pair, in comparison with simple repetition of the target word with a new prime on each presentation. In contrast with other studies of implicit associative encoding that did not use an implicit episodic priming measure, the present study found both age- and DAT-related declines in associative encoding under conditions of massed learning trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive Processing of Emotional Information in Depression, Panic, and Somatoform Disorder.

Emotional Stroop tasks (subliminal/supraliminal exposures), implicit memory tasks (tachistoscopic word identification), and explicit memory tasks (free recall after incidental learning) with 4 word types (physical threat, positive, negative, and neutral words) were administered to patients with major depressive disorder (n = 30), panic disorder (n = 33), somatoform disorder (n = 25), and healthy control participants (n = 33). On the Stroop task, panic patients showed subliminal interferences for physical threat and negative words, depressive patients showed supraliminal interferences for negative words, and somatoform patients showed supraliminal interferences for physical threat words. No patient groups demonstrated implicit memory biases. On the explicit memory task, depressive and panic patients showed memory biases for negative words; somatoform patients showed biases for physical threat words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of environmental support on implicit and explicit memory in younger and older adults.

Addressed (1) whether there are age differences on an implicit word-stem-completion task and (2) whether age differences on both implicit and explicit memory would decrease with increased environmental support. A total of 287 Ss were presented with words in an incidental learning task with structural or semantic processing. Following 2 filler tasks, Ss received an implicit or an explicit word-stem-completion task. The number of letters in the stem varied from 2 to 4. Results yielded an Age?×?Memory Task dissociation such that there were large age differences on the explicit task and no age difference on the implicit task, regardless of whether Ss aware of the memory test were included or excluded. There was no evidence that environmental support improved older adults' performance more than that of younger adults on either memory task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit and explicit memory for shape, body weight, and food-related words in patients with anorexia nervosa and nondieting controls.

Twelve patients with anorexia nervosa and 12 control participants watched a series of 64 words. There were 4 word types: anorexia related, positive, negative, and neutral. The last 3 types were anorexia unrelated. Anorexia-related words had the same affective valence as the neutral control words. Next, the participants completed an explicit memory test ( cued recall ) and an implicit memory test (word stem completion). Results showed a strong explicit memory bias for anorexia-related words for patients with anorexia nervosa but not for nondieting controls. There was no evidence for a similar bias in implicit memory. Results are discussed in the context of cognitive biases in psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired priming on the general knowledge task in amnesia.

The status of priming on the general knowledge test was examined in amnesia. Twenty amnesic and 20 control participants studied words (e.g., CHEETAH) under semantic and nonsemantic encoding conditions and attempted to answer general knowledge questions (e.g., "What is the fastest animal on earth"?) under implicit and explicit retrieval instructions. The measure of memory was how many more test questions participants answered correctly using studied than nonstudied words. Amnesic patients showed impaired memory under implicit and explicit retrieval instructions. Control participants showed equal memory under implicit and explicit retrieval instructions, a result indicating that they engaged in explicit retrieval in both instruction conditions. General-knowledge priming appears to involve explicit retrieval that depends on medial-temporal and diencephalic regions damaged in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal learning strategies in Parkinson's disease.

Word-list learning was studied in patients with Parkinson's disease (PD) and normal control (NC) participants by means of the selective-reminding procedure of H. Buschke and P. A. Fuld (1974) in 3 learning conditions using semantically unrelated items; semantically related items, whose implicit categorical structure had to be spontaneously guessed; and semantically related items, whose explicit categorical structure was known in advance. The PD patients displayed poor learning in all 3 conditions. To identify the functional locus of the PD patients' deficits, the authors performed a stochastic Markov chain analysis, which allowed individual measurements of encoding, retrieval, and category clustering abilities. PD patients were never significantly impaired in encoding word engrams; their impairment was confined to automatic and intentional retrieval and to the ability to benefit from explicit semantic clues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct comparison of two implicit memory tests: Word fragment and word stem completion.

In 3 experiments, the implicit memory tests of word fragment and word stem completion showed comparable effects over several variables: Study of words produced more priming than did study of pictures; no levels-of-processing effect occurred for words; more priming was obtained from pictures when Ss imaged the pictures' names than when they rated them for pleasantness; and forgetting rates were generally similar for the tests. A different pattern of results for the first 3 variables occurred under explicit test conditions with the same word fragments or word stems as cues. It is concluded that the 2 implicit tests are measuring a similar form of perceptual memory. Furthermore, it is argued that both tests are truly implicit because they meet the D. L. Schacter et al (1989) retrieval intentionality criterion: Levels of processing of words have a powerful effect on explicit versions of the tests but no effect on implicit versions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encoding, retrieval, main effects and interactions: Were Lockhart and Craik (1990) on the level?

Investigated whether a main effect of encoding emerges when retrieval tests are equated for difficulty. 132 introductory psychology students were tested in 2 experiments. Ss encoded words semantically or by rhyme, and then judged whether unstudied words were related to studied words. A list structure (L. Jacoby, 1975) was adapted to remove the overall difference in difficulty across semantic and rhyme retrieval tasks. Results indicate no main effect of retrieval task, and the main effect of encoding was not dependent on the retrieval task. Semantic encoding led to a greater likelihood that Ss would judge an unstudied word to be related to a studied word. It was concluded that test words shared either a semantic or a rhyme relation with studied words, the advantage of semantic encoding was not dependent on the retrieval criterion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odors and the remembrance of things past.

Three experiments, using ambient odors and incidental learning procedures, examined the effectiveness of odors as memory retrieval cues. Experiment 1 showed that a single ambient odor present on both learning and testing improved recall of a list of words over a no-odor control and a group that received the odor at encoding or retrieval only. Experiment 2 replicated this result and showed that whereas reinstating the odor context improved overall recall, recall of odor-related information was not significantly enhanced by the odor cue. Finally, Experiment 3, employing implicit and explicit retrieval tasks, demonstrated that the same odor must be present on both learning and remembering for the memory benefit to occur. The memory enhancement observed with odors was not due to the effects of semantic mediation. The results are discussed within the framework of encoding specificity of memory (e.g., E. Tulving and D. M. Thomson, 1973), and implications for odor imagery and cuing effects on odor-related material are addressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)