Explicit and implicit learning of event sequences: Evidence from event-related brain potentials.

Event-related potentials (ERPs) were recorded during a serial reaction time (RT) task, where single deviant items seldom (Experiment 1) or frequently (Experiment 2) replaced 1 item of a repeatedly presented 10-item standard sequence. Acquisition of sequence knowledge was reflected in faster RTs for standard as compared with deviant items and in an enhanced negativity (N2 component) of the ERP for deviant items. Effects were larger for participants showing explicit knowledge in their verbal reports and in a recognition test. The lateralized readiness potential indicated that correct responses were activated with shorter latencies after training. For deviant items, participants with explicit knowledge showed an initial activation of the incorrect but expected response. These findings suggest that the acquisition of explicit and implicit knowledge is reflected in different electrophysiological correlates and that sequence learning may involve the anticipatory preparation of responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of mobilization of knowledge on recognition and recall.

Examined the effect of mobilization of knowledge on recall and recognition in 4 experiments, using 170 undergraduates. In Exp I, the mobilization group generated instances from a specified category and received a study list that contained some of these generated items as well as other members of the category that had not been generated. Control Ss received the same study list after they had generated instances from an irrelevant category. Contrary to previous findings by J. Peeck (see record 1983-22657-001), prior mobilization did not facilitate free recall of the generated study-list items and inhibited recall of nongenerated items. This pattern of recall was replicated in Exp II. The inhibitory effect of prior mobilization on nongenerated items was eliminated in Exp III, which used a recognition memory test. In addition, prior mobilization facilitated the recognition of generated study list items. Exp IV found that when knowledge about the mobilized category was limited, prior mobilization did facilitate free recall but only for generated study-list items. An attempt was made to reconcile data with previous results and to specify the conditions under which mobilization facilitates or inhibits subsequent memory performance. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encoding processes and memory for categorically related words by schizophrenic patients.

Hypothesized that schizophrenics display a deficit in recall relative to recognition (as well as other memory deficits) because they encode the conceptual attributes of to-be-remembered items less frequently than normals. An experimental procedure consisting of 2 phases, incidental learning and long-term retention, was used to test 30 schizophrenics and 26 normal adults. During incidental learning, Ss were presented with 36 short word lists. After each, they recalled a single word that was detectable (i.e., encoded) on the basis of its conceptual category. Two variables were manipulated orthogonally: the probability that items were encoded conceptually and the number of times items were presented. Long-term retention of all items presented during incidental learning was tested in free-recall, category cued recall, and recognition tests, administered in that order. Results show an overriding similarity of schizophrenics to normals in patterns of response to the major variables, providing no support for the hypothesis. Data are consistent, however, with the hypothesis that schizophrenics encode items less elaborately than normals do. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Encoding conditions and the list-strength effect.

The list-strength effect occurs when "strong" items within a list are remembered at the expense of "weak" items within that same list. Two experiments (using 185 college student Ss) showed that variably encoded words were remembered better than words repeated with the same encoding context, whether memory was measured by free recall, frequency estimates, or recognition d'. However, there was little or no evidence from any of the measures that the variably encoded words were recollected in the mixed lists at the expense of the similarly encoded words. This pattern held even though, in Exp 2, there was a list-strength effect on free recall, when list strength was manipulated by increasing the number of presentations of a word. It is concluded that the free recall results could not be accommodated by the model of memory postulated by R. M. Shiffrin et al (see record 1990-13917-001) to account for the effects of list strength. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blocking in category learning.

Many theories of category learning assume that learning is driven by a need to minimize classification error. When there is no classification error, therefore, learning of individual features should be negligible. The authors tested this hypothesis by conducting three category-learning experiments adapted from an associative learning blocking paradigm. Contrary to an error-driven account of learning, participants learned a wide range of information when they learned about categories, and blocking effects were difficult to obtain. Conversely, when participants learned to predict an outcome in a task with the same formal structure and materials, blocking effects were robust and followed the predictions of error-driven learning. The authors discuss their findings in relation to models of category learning and the usefulness of category knowledge in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The efficacy of the generation effect in improving new learning in persons with traumatic brain injury.

Objective: To evaluate the usefulness of the generation effect in improving learning and memory abilities in neurologically impaired individuals. The generation effect is the observation that items self-generated by participants are better remembered than items provided by the examiner. Although this effect has shown to be relatively robust in healthy adults, few studies have examined the usefulness of the generation effect in neurological populations. Participants: 18 individuals with moderate-severe traumatic brain injury (TBI) and 18 healthy adults. Main Outcome Measure: The measure was the generation effect protocol. Results: Results indicated recall and recognition of generated information was significantly higher than that of provided information across testing conditions. However, healthy adults showed greater benefit from the generation effect than did individuals with TBI. As expected, recall and recognition performance diminished over time (i.e., immediate recall, 30 min, 1 week) however, rates of forgetting did not differ between groups. Conclusion: Self-generation significantly improved verbal learning and memory in individuals with TBI. The results of self-generation in improving learning suggest that applying that technique may be beneficial in the cognitive rehabilitation of persons with TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the nature of the decision axis in signal-detection-based models of recognition memory.

Most models of recognition memory involve a signal-detection component in which a criterion is placed along a decision axis. Older models generally assume a familiarity-decision axis, but newer models often assume a likelihood ratio axis instead because it allows for a more natural account of the ubiquitous mirror effect. In 3 experiments reported here, item strength was differentially manipulated to see whether a mirror effect would occur. Within a list, the items from 1 category were strengthened by repetition, but the items from another category were not. On the subsequent recognition test, the hit rate was higher for the strong category, but the false-alarm rates for the weak and strong categories were the same (i.e., no mirror effect was observed). This result suggests that the decision axis represents a familiarity scale and that participants adopt a single decision criterion that they maintain throughout the recognition test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond fast mapping: Young children's extensions of novel words and novel facts.

L. Markson and P. Bloom (1997) concluded that there was evidence against a dedicated system for word learning on the basis of their finding that children remembered a novel word and a novel fact equally well. However, a word-learning system involves more than recognition memory; it must also provide a means to guide the extension of words to additional exemplars, and words and facts may differ with regard to extendibility. Two studies are reported in which 2–4-year-old children learned novel words and novel facts for unfamiliar objects and then were asked to extend the words and facts to additional exemplars of the training objects. In both studies, children extended the novel word to significantly more category members than they extended the novel fact. The results show that by 2 years of age, children honor the necessary extendibility of novel count nouns but are uncertain about the extendibility of arbitrary facts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous backward conditioned inhibition and mediated conditioning.

Demonstrations of retrospective revaluation suggest that remembered stimuli undergo a reduction in association with the unconditioned stimulus (US) present during learning. Conversely, demonstrations of mediated conditioning in flavor-conditioning experiments with rats suggest that remembered stimuli undergo an increase in association with the US present during learning. In a food allergy prediction task with 23 undergraduates, we demonstrated simultaneous backward conditioned inhibition and mediated conditioning effects. These results are compatible with the hypothesis that the direction of change (decrease or increase) in associative strength depends on whether the remembered stimulus was of a different category (conditioned stimulus/antecedent) or the same category (US/outcome) as the presented US. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Learning and retention through predictive inference and classification.

Work in category learning addresses how humans acquire knowledge and, thus, should inform classroom practices. In two experiments, we apply and evaluate intuitions garnered from laboratory-based research in category learning to learning tasks situated in an educational context. In Experiment 1, learning through predictive inference and classification were compared for fifth-grade students using class-related materials. Making inferences about properties of category members and receiving feedback led to the acquisition of both queried (i.e., tested) properties and nonqueried properties that were correlated with a queried property (e.g., even if not queried, students learned about a species' habitat because it correlated with a queried property, like the species' size). In contrast, classifying items according to their species and receiving feedback led to knowledge of only the property most diagnostic of category membership. After multiple-day delay, the fifth-graders who learned through inference selectively retained information about the queried properties, and the fifth-graders who learned through classification retained information about the diagnostic property, indicating a role for explicit evaluation in establishing memories. Overall, inference learning resulted in fewer errors, better retention, and more liking of the categories than did classification learning. Experiment 2 revealed that querying a property only a few times was enough to manifest the full benefits of inference learning in undergraduate students. These results suggest that classroom teaching should emphasize reasoning from the category to multiple properties rather than from a set of properties to the category. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Storage and retrieval of associative clusters: A stages-of-learning analysis of associative memory traces.

In this research, the assumptions underlying the unitary trace theory of item representation and acquisition were tested in two cued-recall experiments in which the degree of preexperimental knowledge (typicality) was manipulated. Subjects learned lists of word triads (each of which consisted of a single cue and two targets) to a stringent acquisition criterion. In Experiment 1, typicality was manipulated in the absence of semantic relationships between members of the associative clusters. In Experiment 2, semantic relationships were present among cluster members, and preexperimental knowledge was manipulated by varying the degree of intracluster category membership as measured by whether cue and target items were typical or atypical category exemplars. In both experiments a mathematical model that embodies stages-of-learning distinctions was used to analyze the acquisition data. The results indicated that (1) cues and targets were represented in a single holistic memory trace, and (2) the manipulation of the degree of preexperimental knowledge affected both trace storage and retrieval learning, but had only a minimal impact on retrieval performance between the time a trace was stored and the time retrieval learning was complete. It was argued that these findings are consistent with a single unitary trace interpretation, namely, the modified storage-retrieval model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and memory for expected and unexpected objects in real-world settings.

Adult age differences in the consistency effect were examined in 3 experiments. The consistency effect refers to items inconsistent with expectations being better remembered than items consistent with expectations. Younger and older adults walked into an office room and viewed objects that varied in their consistency with expectation. Immediate and delayed recognition tests on item information (i.e., distractors were defined by their semantic identity) revealed that both age groups recognized unexpected items better than expected items. However, when recognition of token information was requested (i.e., distractors were defined by their physical appearance), younger adults, in contrast to older adults, exhibited consistency effects. Also, under divided attention, young adults revealed the same pattern of data as did elderly adults under full attention. The results are discussed in terms of capacity-related differences in distinctive encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directed Forgetting in Incidental Learning and Recognition Testing: Support for a Two-Factor Account.

Instructing people to forget a list of items often leads to better recall of subsequently studied lists (known as the benefits of directed forgetting). The authors have proposed that changes in study strategy are a central cause of the benefits (L. Sahakyan & P. F. Delaney, 2003). The authors address 2 results from the literature that are inconsistent with their strategy-based explanation: (a) the presence of benefits under incidental learning conditions and (b) the absence of benefits in recognition testing. Experiment 1 showed that incidental learning attenuated the benefits compared with intentional learning, as expected if a change of study strategy causes the benefits. Experiment 2 demonstrated benefits using recognition testing, albeit only when longer lists were used. Memory for source in directed forgetting was also explored using multinomial modeling. Results are discussed in terms of a 2-factor account of directed forgetting. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Learning about categories that are defined by object-like stimuli despite impaired declarative memory.

Exposure to members of a category facilitates later categorization of similar but novel instances of the category. Past studies have suggested that category knowledge can be acquired implicitly and independently of declarative memory. However, these studies have relied on dot pattern stimuli that, unlike most real-world objects, are difficult to verbalize and cannot be broken into component features. It is therefore unclear how relevant such studies are to an understanding of everyday categorization. In the present studies, category learning in amnesic patients was tested with stimuli that both exhibit discrete features and are easy to describe (namely, cartoon animals). Amnesic patients were as competent as healthy volunteers in learning to categorize these animals, despite their impairment in recalling the animals' features. The results suggest that the implicit acquisition of category knowledge is a common process in everyday experience, and that it can occur whenever individuals encounter a large group of related items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of relevance shifts in category acquisition: A test of neural networks.

The effect of changing the validity of stimulus dimensions in the course of category learning was investigated. Contrary to previous experiments on interdimensional relevance shifts, a family resemblance stimulus structure was used that allowed for the direct comparison of performance on items learned before and after the relevance shift. In both experiments, the test performance was dominated by information that was acquired after the relevance shift. The results indicate that the acquired knowledge of the 2 learning phases was not integrated, but knowledge learned before the shift was partly replaced by information acquired after the shift. Simulation of the results by the independent cue model, the configural cue model, and ALCOVE (attention learning covering map) demonstrates that these models must be expanded by a mechanism that inhibits the integration of information acquired before and after the relevance shift. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thirty-Something Categorization Results Explained: Selective Attention, Eyetracking, and Models of Category Learning.

An eyetracking study testing D. L. Medin and M. M. Schaffer's (1978) 5-4 category structure was conducted. Over 30 studies have shown that the exemplar-based generalized context model (GCM) usually provides a better quantitative account of 5-4 learning data as compared with the prototype model. However, J. D. Smith and J. P. Minda (2000) argued that the GCM is a psychologically implausible account of 5-4 learning because it implies suboptimal attention weights. To test this claim, the authors recorded undergraduates' eye movements while the students learned the 5-4 category structure. Eye fixations matched the attention weights estimated by the GCM but not those of the prototype model. This result confirms that the GCM is a realistic model of the processes involved in learning the 5-4 structure and that learners do not always optimize attention, as commonly supposed. The conditions under which learners are likely to optimize attention during category learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From chair to "chair": A representational shift account of object labeling effects on memory.

What are the consequences of calling things by their names? Six experiments investigated how classifying familiar objects with basic-level names (chairs, tables, and lamps) affected recognition memory. Memory was found to be worse for items that were overtly classified with the category name--as reflected by lower hit rates--compared with items that were not overtly classified. This effect of labeling on subsequent recall is explained in terms of a representational shift account, with labeling causing a distortion in dimensions most reliably associated with the category label. Consistent with this account, effects of labeling were strongly mediated by typicality and ambiguity of the labeled items, with typical and unambiguous items most affected by labeling. Follow-up experiments showed that this effect cannot be explained solely by differences in initial encoding, further suggesting that labeling a familiar image distorts its encoded representation. This account suggests a possible mechanism for the verbal overshadowing effect (J. W. Schooler & T. Y. Engstler-Schooler, 1990). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of list format and category headers on age differences in understanding medication instructions

We examined whether instructions are better understood and remembered when they contain organizational cues. Our previous research found that older and younger adults organize medication information in similar ways, suggesting that they have a schema for taking medication. In the present study, list formats (vs. paragraphs) emphasized the order of information and category headers emphasized the grouping of information specified by this schema. Experiment 1 examined whether list and header cues improve comprehension (answer time and accuracy) and recall for adults varying in age and working memory capacity (measured by a sentence span task). List instructions were better understood and recalled than paragraphs, and reduced age differences in answer time and span differences in accuracy. Headers reduced paragraph comprehension for participants with lower levels of working memory capacity, presumably because they were not salient cues in the paragraphs. Experiment 2 investigated if headers were more effective when more saliently placed in paragraphs and lists, and if list and header cues helped readers draw inferences from the instructions. List formats again reduced age differences in comprehension, especially reducing the time needed to draw inferences about the medication. While headers did not impair comprehension, these cues did impair recall. The present study suggests that list-organized instructions provide an environmental support that improves both older and younger adult comprehension and recall of medication information.