Null category-length and target–lure relatedness effects in episodic recognition: A constraint on item-noise interference models

There are two main classes of model of interference effects in recognition memory: item-noise and context-noise. Item-noise models predict that a loss of memory discriminability will occur with an increase in the number of studied items from the same taxonomic category (category length, CL) and that forced-choice recognition performance will be higher when the target and lure are related rather than unrelated. Context-noise models, however, predict null effects for both of these manipulations. Although results from some recent experiments suggest that CL and target–lure relatedness have a trivial or no effect on memory discriminability when the related items from the same taxonomic category are “not back to back in the study list but are separated (spaced) by interleaving items from other semantic categories,” these experiments have methodological limitations that were eliminated in the present experiment in which exemplars representing category lengths of 2, 8, or 14 were presented spaced apart within the same study list. Recognition was tested using a yes/no recognition test or a two-alternative forced-choice recognition test in which the target and lure were either related or unrelated. In yes/no recognition, d′ decreased as CL increased, replicating prior research. However, when the slope of the z-ROC function is less than 1.0, as is typically so and was so in the present results, d′ differences can arise due to criterion shifts and are not necessarily due to memory discriminability differences. When the more appropriate measure of memory discriminability, d _a , was computed, CL had no effect in yes/no recognition, nor did it have an effect in forced-choice recognition, which also was not affected by target–lure relatedness. Thus, the present results are congruent with context-noise models and pose a challenge for item-noise models.     

The ironic effect of guessing: increased false memory for mediated lists in younger and older adults

Younger and older adults studied lists of words directly (e.g., creek, water) or indirectly (e.g., beaver, faucet) related to a nonpresented critical lure (CL; e.g., river). Indirect (i.e., mediated) lists presented items that were only related to CLs through nonpresented mediators (i.e., directly related items). Following study, participants completed a condition-specific task, math, a recall test with or without a warning about the CL, or tried to guess the CL. On a final recognition test, warnings (vs. math and recall without warning) decreased false recognition for direct lists, and guessing increased mediated false recognition (an ironic effect of guessing) in both age groups. The observed age-invariance of the ironic effect of guessing suggests that processes involved in mediated false memory are preserved in aging and confirms the effect is largely due to activation in semantic networks during encoding and to the strengthening of these networks during the interpolated tasks.     

Explaining developmental reversals in false memory

We report the first demonstration that a simple, theory-driven manipulation produces opposite developmental trends in false memory for the same information. When 6-, 10-, and 14-year-olds studied lists containing exemplars of familiar taxonomic categories, false memory for the same unpresented items (category exemplars and labels) increased with age if list items were semantically related but decreased with age if semantic relations could not be formed among list items. A control experiment ruled out the hypothesis that these results were due to young children having generic deficits in forming relations among list items.     

Memory search: When does semantic analysis occur?

This study was addressed to the determination of the stage at which semantic analysis occurs during a STM recognition task. A list of exemplars (memory set), drawn from 13 different categories, was presented at a rate of 11/2 sec/item, followed by a category name probe. Ss then indicated whether any of the exemplars in the memory set belonged to that category. List length was varied from 5 to 7, with each memory set containing items from either two or three categories. It was found that RT was independent of list length, but did increase by 60 msec as the number of categories represented in the list increased from two to three. From this, it was concluded that activation of a superordinate category representation occurred upon presentation of each memory-set item, and that the memory scan was done on these superordinate categories.     

The breadth of memory search

The recall of previously studied items is widely believed to incorporate a search of a markedly constrained set of possibilities, and the present study examines whether this set of items typically includes unstudied semantic associates of the study items. In an episodic task, participants recalled a previously studied list of eight exemplars drawn from a small or large category, and, in a semantic task, participants generated exemplars from these categories. Category size affected the time course of recall in the semantic task but not in the episodic task. This empirical dissociation between episodic and semantic memory is consistent with the view that episodic memory search efficiently excludes unstudied semantic associates of the study items and is instead constrained to those items sharing the temporal and spatial attributes of the episode.     

Two routes for activation in the priming of categorical coordinates

The authors operationalized category priming as participants' recognition facilitation of nonstudied, low semantically similar exemplars by studied exemplars in a category. The existing literature either does not examine the effect of studied exemplars on nonstudied exemplars in a category or fails to show an appreciable amount of category priming. In 2 experiments, the authors demonstrated a unique process to account for the category priming effect and distinguish it from the semantic priming effect, facilitation of semantically similar exemplars, in the context of a category. In Experiment 1A, the authors used a multidimensional scaling technique to examine participants' internal structure of different categories. In Experiment 1B, the authors used a lexical decision task that used these internal structures to show that semantic encoding of category exemplars causes activation of existing category knowledge in memory. Consequently, participants easily recognized nonstudied, low semantically similar exemplars in a category. However, recognition facilitation between high semantically similar exemplars did not require category knowledge activation.     

The impact of retrieval suppression on conceptual implicit memory

ABSTRACT

When people suppress retrieval of episodic memories, it can induce forgetting on later direct tests of memory for those events. Recent reports indicate that suppressing retrieval affects less conscious, unintentional retrieval of unwanted memories as well, at least on perceptually-oriented indirect tests. In the current study we examined how suppressing retrieval affects conceptual implicit memory for the suppressed content, using a category verification task. Participants studied cue-target words pairs in which the targets were exemplars of 22 semantic categories, such as vegetables or occupations. They then repeatedly retrieved or suppressed the targets in response to the cues for some of those pairs. Afterwards, they were exposed to the targets intermixed with novel items, one at a time, and asked to verify the membership of each of the words in a semantic category, as quickly as possible. Judgment response times to studied words were faster than to unstudied exemplars, reflecting repetition priming, as has been previously observed. Strikingly, the beneficial effects of prior exposure on response time were eliminated for targets that had been suppressed. Follow-up explicit memory tests also demonstrated that retrieval suppression continued to disrupt episodic recall for the items that had been just been re-exposed on the category verification test. These findings support the contention that the effects of retrieval suppression are not limited to episodic memory, but also affect indirect expressions of those memories on conceptually oriented tests, raising the possibility that underlying semantic representations of suppressed content are affected.     

The influence of age on memory for distinctive events

We examined whether memory for distinctive events is influenced by aging. To do so, we used a semantic isolation paradigm in which people show superior memory for a word when it is presented in a list of items from a different semantic category (e.g., the word table is presented in a list of all bird exemplars) as compared with when the same word (table) is presented in a list of unrelated words. Results showed that both younger and older adults demonstrated an isolation effect in memory, although older adults showed a numerically smaller isolation effect than did younger adults. Results suggest that in contrast with previous findings (Cimbalo & Brink, 1982), older adults can take advantage of this type of distinctiveness to aid memory performance.     

Retention performance as a function of the distinctiveness of memory traces and retention task

Summary In the acquisition phase of an incidental learning paradigm, words that are exemplars of categories were judged as to whether or not they belonged to a specified category. This was followed by a forced choice recognition task. The effects of three variables were studied: a) whether the acquisition task called for a positive or a negative response; b) the number of exemplar words per category; and c) whether distractor items in the recognition test came from the same category as the target words or from other categories. The results showed that recognition errors were influenced by all three variables. Unlike the variables a) and c) which showed significant main effects, the effect of number of exemplars per category was significant only for the same category distractor condition. In this condition more exemplars per category led to more recognition errors. The results are explained by assuming that retention performance is determined by two factors. The first factor is the distinctiveness of the memory traces. This is supposed to be a joint product of task-specific encoding and stimulus characteristics. The second factor is the distinctive similarity between the retrieval information and the stored memory traces. Although the results show some sublte effects that are not easy to explain, it is argued that this model offers a good account of the general findings.     

On the durability of retrieval-induced forgetting

Information retrieved from memory becomes more recallable in the future than it would have been otherwise. Competing information associated with the same cues, however, tends to become less recallable, at least for a while. Whether the latter effect—referred to as retrieval-induced forgetting—is persistent, or only transient, is the question that motivated the present research. Participants studied category-exemplar pairs, practised retrieving other exemplars of half the categories, and, finally, were tested for their ability to recall initially studied exemplars after a 5-min delay (half the items) and after 1 week (the remaining items). In addition, for half the categories, opportunities to restudy the exemplars were provided between cycles of retrieval practice. The results demonstrate that retrieval-induced forgetting can persist for as long as a week, but that such forgetting is eliminated when participants are intermittently reexposed to unpractised items during retrieval practice.     

ROCs in recognition with and without identification

Receiver operating characteristics (ROCs) for the recognition of unidentified word fragments were analysed and compared with ROCs for the recognition of identified word fragments. In all conditions reported here, the z-transformed ROCs (z-ROCs) for recognition without identification were linear, with slopes near 1.0. In contrast, the z-ROCs for recognition with identification each had both a linear and a quadratic component, and a slope of substantially less than 1.0. Because the recognition of unidentified word fragments likely results from a familiarity process, the present study examined how well the effect can be explained by global matching variants of signal detection theory. Global matching models predict that memory should be better for strong items from a mixed list than for strong items from a pure list, and should be worse for weak items from a mixed list than for weak items from a pure list; however, only the latter pattern was shown for the recognition of unidentified items.     

A rule-based categorization deficit in Alzheimer's disease?

This study examined the categorization processes that Alzheimer's disease (AD) patients use during assessments of semantic memory. Rule-based categorization involves the careful, analytic processing of strict criteria to determine category membership, particularly for items from graded categories with ambiguous category membership; similarity-based categorization requires an overall comparison of a test stimulus with a prototype or remembered exemplar of the category and is relatively effective for the rapid categorization of items with unambiguous category membership. To assess these processes in AD, patients were asked to decide the category membership of test stimuli for categories with poorly defined or fuzzy boundaries (e.g., VEGETABLE) and for categories with well-defined boundaries (e.g., FEMALE) and then to judge the representativeness of the test stimulus for its chosen category. A subgroup of AD patients demonstrated a typical pattern of impaired semantic memory compared to healthy control subjects; that is, difficulty deciding the category membership of test items from fuzzy categories. Among these patients, we found no deficit in category membership decisions about items taken from well-defined categories. We also found that AD patients and healthy controls do not differ in their representativeness judgments of items within a correctly judged category. These findings are most consistent with the hypothesis that rule-based categorization difficulty limits semantic memory in AD.     

The Experimental Measurement of a Social Hierarchy in Gallus Domesticus: VI. Preliminary Identification of Social Law

Bousfield and Sedgewick showed that the cumulative number of associations produced to a category as a function of time could be described by an exponential function having the parameters m (rate of association) and C (total number of associates produced). In two experiments using male and female college students (N = 16 and N = 14, respectively), the present study investigated the hypothesis suggested by previous research, that the values of m and C for different categories are negatively correlated. S s produced examples of different categories in four-minute periods per category on mimeographed sheets. The predicted negative correlation across categories was found (Experiment I, r = .54, p < .05, one-tailed test; Experiment 2, r = .75, p < .01). Categories with a low m value had a high C value and vice versa. The effect can be explained by a model which assumes exemplars are stored more or less densely in semantic memory.     

Chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) show the isolation effect during serial list recognition memory tests

The isolation effect (or von Restorff effect) occurs when one item in a to-be-remembered list is distinctive from all remaining items, and memory for that item is enhanced. Four chimpanzees were presented with a serial list of four photographs. In the homogeneous condition, all list items were from the same semantic category (e.g., four fruits). In the isolate condition, three items were from the same category, but the fourth item (the isolate) was from a different category (e.g., three fruits and one toy). Then, two photographs were presented, and the chimpanzees had to select the one that was from the list. Two of four chimpanzees were significantly more likely to select a correct isolate item than an item from the same list position in the homogeneous condition for at least some list positions. This facilitation in performance was for isolate items only, as presenting an isolate item in a list did not facilitate greater recognition of other list items compared to the homogeneous condition. These results indicated that some chimpanzees perceived the semantic categories of the photographs, and categorization of photographs led to the isolation effect. Thus, chimpanzees may share with humans some aspects of memory organization that involve spontaneously categorizing visual stimuli and recognizing categorically unique stimuli.     

An interactive activation approach to object processing: Effects of structural similarity,name frequency,and task in normality and pathology

Abstract

We present a computational model of the processes involved in retrieving stored semantic and name information from objects, using a simple interactive activation and competition architecture. We simulate evidence showing a cross-over in normal reaction times to make semantic classification and identification responses to objects from categories with either structurally similar or structurally dissimilar exemplars, and that identification times to objects from these two different classes correlate differentially with measures of the structural similarity of objects within the category and the frequency of the object's name. Structural similarity exerts a negative effect on object decision as well as naming, though this effect is larger on naming. Also, on naming, structural similarity interacts with the effects of name frequency, captured in the model by varying the weight on connections from semantic to name units; frequency effects are larger with structurally dissimilar items. In addition, (1) the range of potential errors for objects from these two classes, when responses are elicited before activation reached a stable state, differ–a wider range of errors occur to objects from categories with structurally similar exemplars; and (2) simulated lesions to different locations within the model produce selective impairments to identification but not to semantic classification responses to objects from categories with structurally similar exemplars. We discuss the results in relation to data on visual object processing in both normality and pathology.     

Enhanced recognition of words previously presented in a task with nonfocal prospective memory requirements

Remembering to perform deferred actions when events are encountered in the future is referred to as event-based prospective memory. Individuals can be slower to respond to ongoing tasks when they have prospective memory task requirements. These costs are interpreted as evidence for cognitive control processes allocated to the prospective memory task, but we know little about these processes. In the present article, the recognition of nontargets previously presented in an ongoing task with prospective memory task requirements provided evidence for the differential processing of individual ongoing task items. Participants performed a lexical decision task, where some participants were required to make an alternative prospective memory response either to a specific word (focal) or to exemplars of a category (nonfocal). Participants were slower to respond to the ongoing task in the nonfocal conditions than in the control condition (costs), regardless of whether or not prospective memory task importance was emphasized. Participants were also slower to respond to the ongoing task in the focal conditions than in the control condition, but only when prospective memory task importance was emphasized. This task was followed by a surprise recognition memory test in which nontarget words from the lexical decision task were intermixed with new words. Focal conditions, but not nonfocal conditions, showed better discrimination on the recognition task, as compared with the control condition. Participants in nonfocal conditions mapped the semantic features of the ongoing task letter strings onto the semantic features of their prospective memory category, and this elaboration in the processing of individual nontargets increased incidental learning and produced the recognition benefit.     

Preservation of categorical knowledge in Alzheimer's disease: A computational account

Abstract

The distinction between knowledge of specific exemplars and knowledge of their general categories is central to much theorising on the nature of semantic memory. The dissociation between exemplar and category knowledge observed in Alzheimer's Disease (AD) would appear to support this distinction, and to suggest that different neural systems are involved in the representation of exemplar and category knowledge. We review the evidence for preserved category knowledge in the semantic memory impairment of AD, and propose an alternative interpretation, according to which category and exemplar knowledge are both represented in the same distributed neural substrate. The relative preservation of category knowledge is a consequence of the greater frequency, and hence greater robustness, of the representation of attributes shared by all or most members of a category, compared to exemplar-unique attributes. We test and confirm the computational adequacy of this hypothesis in two computer simulations.     

To what extent does typicality boost semantic priming effects between members of their categories?

Atypical items of their semantic category yield more generalisation than their typical members when relearning in connectionist networks (Plaut, D. C. (1996). Relearning after damage in connectionist networks: toward a theory of rehabilitation. Brain and Language, 52(1), 25–82) and in empirical studies (Kiran, S., & Thompson, C. K. (2003). The role of semantic complexity in treatment of naming deficits: Training semantic categories in fluent aphasia by controlling exemplar typicality. Journal of Speech, Language, and Hearing Research, 46(4), 773–787). It seems therefore that atypical words provide more information about the overall structure of the semantic category due to their specific and shared features. In this view, atypical primes could strongly facilitate the processing of targets compared to typical primes, because typical primes contain little information about the variation between members within a category. In contrast, three semantic priming experiments in visual word recognition showed an advantage with the typical context, but not with the atypical one. These findings were observed in a variety of tasks, including lexical decision, categorisation and semantic judgment. Our results do not support the findings about generalisation in relearning and suggest that typicality effects in semantic priming mostly come from the activation of representative features of categories.     

Retrieval‐induced forgetting: A developmental study

Two studies examined the possibility of retrieval‐induced forgetting by 7‐year‐olds. Children heard a story while viewing pictures of events mentioned in the story, each highlighting objects drawn from two distinct semantic categories (e.g. animals and food). Over the next several days, children were asked the same yes/no questions about half the examples from one category and, finally, were tested for their memory of the complete set of examples from both categories. Both a category‐cued recall test (Study 1) and a written recognition‐memory test (Study 2) produced results suggestive of retrieval‐induced forgetting. That is, children showed poorer memory for unpractised items from the practised category than for unpractised items from the other category. The severity of the effect did not differ reliably between the children and young adults, and was unaffected by whether practised items appeared before or after the unpractised competitors (Study 2). We consider the implications of these findings for competing views about retrieval‐induced forgetting and the development of cognitive inhibition.     

Category width and differentiation in semantic categories

The hypothesis that the judgemental categorizing behaviour measured by Pettigrew's Category-Width scale is linked to semantic categorization is investigated. Individual differences in broad vs. narrow categorizing behaviour measured by the C-W scale are reconceptualized within the framework of Rosch's (1977) theory of human categorization. Two extreme groups on the C-W scale, broad categorizers and narrow categorizers, were selected as subjects. One experiment employed a short-term release-from-proactive-inhibition paradigm. The amount of discrepancy in recall between the preshift and the shift trials was used as an index to perceived semantic distance. The result showed that narrow categorizers perceived the same fuzzy items in a semantic category as less similar to the good exemplars of that category than broad categorizers did. In a further experiment using a semantic-categorization technique, narrow categorizers judged the same fuzzy items as category members less frequently than broad categorizers did, indicating that narrow categorizers possess more differentiated semantic categories than do broad categorizers. These findings are seen as an extension of the differential categorizing behaviour on artificial categories in the C-W scale to semantic categorization for which there is a pre-existing system.