Semantic satiation affects category membership decision time but not lexical priming

Experiments 1 and 2 examined the effects of semantic satiation on category membership decision latency. Subjects overtly repeated the name of a category either 3 or 30 times, and then decided whether or not a target exemplar was a member of the repeated category. Experiment 1 obtained some evidence that member decisions are slower and nonmember decisions are faster following 30 repetitions, but only the interaction was reliable. Experiment 2 confirmed only that member decisions are slower following satiation of the category name. The results support the hypothesis that prolonged repetition of a word reduces the availability of semantic information related to that word. Experiment 3 showed that the magnitude of priming in the lexical decision task is unaffected by satiation of the prime. Several general approaches to understanding semantic satiation are discussed. The most parsimonious account assumes that satiation affects the links or pathways connecting concepts in the satiated category. The net effect is to decrease the rate of search and associative spread of activation in conceptual structures.     

Aging affects motor learning but not savings at transfer of learning

Two important components of skill learning are the learning process itself (motor acquisition) and the ability to transfer what has been learned to new task variants (motor transfer). Many studies have documented age-related declines in the ability to learn new manual motor skills. In this study, I tested whether the degree of savings at transfer of learning is similarly affected by advancing age. Young and older adults made aiming movements with a joystick to hit targets presented on a computer screen, with real-time feedback display of their movement. They adapted to three different rotations of the feedback display in a sequential fashion, with return to the normal feedback display between each. Adaptation performance was better when it was preceded by other adaptive experiences, regardless of age.     

Collaboration in implicit memory: evidence from word-fragment completion and category exemplar generation

Psychological Research - Recent studies have begun to investigate the effects of collaboration on explicit tests such as free recall, cued recall, and recognition. In contrast, little is known...     

Auditory and visual word-stem completion: Separating data-driven and conceptually driven processes

Two experiments investigated the contributions of data-driven and conceptually driven processing on an implicit word-stem completion task. In Experiment 1, individual words were studied either visually or auditorily and were tested using either visual or auditory word-stems. Keeping modality the same from study to test led to more priming than did changing modality, but there was reliable cross-modal priming. In Experiment 2, subjects read sentences like The boat travelled underwater and inferred the subject noun (i.e. “submarine”) or sentences like The submarine travelled underwater and categorized the subject noun (i.e. “boat”). At test, there was reliable priming for both actually read nouns and inferred nouns. In addition, a modality effect was evident for the actually read nouns but not for the inferred nouns. Taken together, these results imply that there is a basic conceptually driven contribution to priming plus an additional contribution of data-driven processing when surface form is the same at study and test.     

A comparison of serial position effects in implicit and explicit word-stem completion

In this study I examined a further possible dissociation between implicit and explicit memory—whether implicit memory produces serial position effects that are similar to those found in explicit memory. When implicit word-stem completion and explicit word-stem cued recall were compared, only the explicit test showed significant primacy and recency effects. The explicit test was sensitive to the order in which stimuli words were encoded, but the implicit test was not. This dissociation between implicit and explicit memory provides further evidence that conscious retrieval processes were not involved in the implicit test.     

Posterror slowing predicts rule-based but not information-integration category learning

We examined whether error monitoring, operationalized as the degree to which individuals slow down after committing an error (i.e., posterror slowing), is differentially important in the learning of rule-based versus information-integration category structures. Rule-based categories are most efficiently solved through the application of an explicit verbal strategy (e.g., “sort by color”). In contrast, information-integration categories are believed to be learned in a trial-by-trial, associative manner. Our results indicated that posterror slowing predicts enhanced rule-based but not information-integration category learning. Implications for multiple category-learning systems are discussed.     

TMS to the “occipital face area” affects recognition but not categorization of faces

The human cortical system for face perception is comprised of a network of connected regions including the middle fusiform gyrus (“fusiform face area” or FFA), the inferior occipital cortex (“occipital face area” or OFA), and the superior temporal sulcus. The traditional hierarchical feedforward model of visual processing suggests information flows from early visual cortex to the OFA for initial face feature analysis to higher order regions including the FFA for identity recognition. However, patient data suggest an alternative model. Patients with acquired prosopagnosia, an inability to visually recognize faces, have been documented with lesions to the OFA but who nevertheless show face-selective activation in the FFA. Moreover, their ability to categorize faces remains intact. This suggests that the FFA is not solely responsible for face recognition and the network is not strictly hierarchical, but may be organized in a reverse hierarchical fashion. We used transcranial magnetic stimulation (TMS) to temporarily disrupt processing in the OFA in neurologically-intact individuals and found participants’ ability to categorize intact versus scrambled faces was unaffected, however face identity discrimination was significantly impaired. This suggests that face categorization but not recognition can occur without the “earlier” OFA being online and indicates that “lower level” face category processing may be assumed by other intact face network regions such as the FFA. These results are consistent with the patient data and support a non-hierarchical, global-to-local model with re-entrant connections between the OFA and other face processing areas.     

Ageing affects conceptual but not perceptual memory processes

Whereas age effects commonly occur in tests of explicit memory, tests of implicit memory often show age invariance. In two experiments, the traditional confound between test type (implicit vs explicit) and retrieval process (conceptually driven vs perceptually driven) was removed by using conceptually driven and perceptually driven tests of both implicit and explicit memory. Experiment 1 revealed a significant age effect for conceptually driven retrieval and no age effect for perceptually driven retrieval, regardless of the type of memory being measured. Experiment 2 highlighted a difference between the two age groups in their ability to utilise semantic encoding in a nominally perceptually driven explicit memory test. The paper concludes that although perceptually driven processing is stable over age, particular care must be taken to minimise contamination from conceptually driven retrieval processes in such investigations.     

Bilingualism affects picture naming but not picture classification

Bilinguals named pictures in their dominant language more slowly (and with more errors) than did monolinguals. In contrast, bilinguals named the same pictures as quickly as did monolinguals on the fifth presentation (in Experiment 2) and classified them (as human made or natural) as quickly and accurately as did monolinguals (in Experiment 1). In addition, bilinguals retrieved English picture names more quickly if they knew the name in both Spanish and English (on the basis of a translation test that bilinguals completed after the timed tasks), and monolingual response times for the same materials suggested that this finding was not obtained simply because names that were easier to translate were easier in general. These findings suggest that bilinguals differ from monolinguals at a postconceptual processing level, that implicit activation of lexical representations in the nontarget language can facilitate retrieval in the target language, and that being bilingual is analogous to having a lexicon full of lower frequency words, relative to monolinguals.     

How category learning affects object representations: not all morphspaces stretch alike

How does learning to categorize objects affect how people visually perceive them? Behavioral, neurophysiological, and neuroimaging studies have tested the degree to which category learning influences object representations, with conflicting results. Some studies have found that objects become more visually discriminable along dimensions relevant to previously learned categories, while others have found no such effect. One critical factor we explore here lies in the structure of the morphspaces used in different studies. Studies finding no increase in discriminability often use blended morphspaces, with morphparents lying at corners of the space. By contrast, studies finding increases in discriminability use factorial morphspaces, defined by separate morphlines forming axes of the space. Using the same 4 morphparents, we created both factorial and blended morphspaces matched in pairwise discriminability. Category learning caused a selective increase in discriminability along the relevant dimension of the factorial space, but not in the blended space, and led to the creation of functional dimensions in the factorial space, but not in the blended space. These findings demonstrate that not all morphspaces stretch alike: Only some morphspaces support enhanced discriminability to relevant object dimensions following category learning. Our results have important implications for interpreting neuroimaging studies reporting little or no effect of category learning on object representations in the visual system: Those studies may have been limited by their use of blended morphspaces.     

Ageing affects conceptual but not perceptual memory processes

Whereas age effects commonly occur in tests of explicit memory, tests of implicit memory often show age invariance. In two experiments, the traditional confound between test type (implicit vs explicit) and retrieval process (conceptually driven vs perceptually driven) was removed by using conceptually driven and perceptually driven tests of both implicit and explicit memory. Experiment 1 revealed a significant age effect for conceptually driven retrieval and no age effect for perceptually driven retrieval, regardless of the type of memory being measured. Experiment 2 highlighted a difference between the two age groups in their ability to utilise semantic encoding in a nominally perceptually driven explicit memory test. The paper concludes that although perceptually driven processing is stable over age, particular care must be taken to minimise contamination from conceptually driven retrieval processes in such investigations.     

Disrupting feedback processing interferes with rule-based but not information-integration category learning

The effect of a sequentially presented memory scanning task on rule-based and information-integration category learning was investigated. On each trial in the short feedback-processing time condition, memory scanning immediately followed categorization. On each trial in the long feedback-processing time condition, categorization was followed by a 2.5-sec delay and then memory scanning. In the control condition, no memory scanning was required. Rule-based category learning was significantly worse in the short feedback-processing time condition than in the long feedback-processing time condition or control condition, whereas information-integration category learning was equivalent across conditions. In the rule-based condition, a smaller proportion of observers learned the task in the short feedback-processing time condition, and those who learned took longer to reach the performance criterion than did those in the long feedback-processing time or control condition. No differences were observed in the information integration task. These results provide support for a multiple-systems approach to category learning and argue against the validity of single-system approaches.     

Target-flanker discriminability affects conflict size but not sustained suppression

On successive trials, repetitions of irrelevant information often tend to reduce congruency effects as compared to alternations of irrelevant information. The preferred explanation for this congruency modulation is the sustained-suppression hypothesis, suggesting that suppression of the irrelevant information on a given trial perseveres into the subsequent trial. However, in contrast to the generality of this idea, this modulation is only stable when the irrelevant information contains spatial features, which coincided in the existing research with large conflict sizes and response conflicts. In two arrow flanker experiments, we investigated whether the congruency modulation depends on the size of the conflict, by manipulating the saliency of the target (Experiment 1) and the flankers (Experiment 2). Although these manipulations affected the size of the conflict caused by the flankers, neither experiment showed an influence of conflict size on the reduction of the congruency effect for repetitions as compared to alternation of the irrelevant flankers. We conclude that sustained-suppression is not a consequence of large conflicts, at least if sustained-suppression causes the congruency modulation.     

Spelling-to-sound regularity affects pronunciation latency but not lexical decision

Summary A series of experiments are reported concerning the regularity effect in single- word pronunciation and lexical decision tasks. Experiment 1 compared pronunciation latencies for exception words based on unfamiliar letter patterns (e.g., YACHT) with exception words based on common letter patterns (e.g., PINT). It was found that both types of exceptions produced longer latencies than regular words. Experiment 2 employed a more objective basis for matching exception and regular words for letter pattern familiarity. Under these conditions exception words still produced significantly longer pronunciation latencies than regular words. These experiments show that previous demonstrations of the regularity effect in pronunciation cannot be attributed to uncontrolled visual differences between exception and regular words. Experiment 3 investigated whether the same material as Experiment 2 would produce a regularity effect in lexical decision but this was not found. Theoretical implications of these resuts and discrepancies with previous studies are discussed.     

Hypermnesia occurs in recall but not in recognition

Two experiments investigated the effect of encoding conditions and type of test (recall vs. recognition) on the phenomenon of hypermnesia (improved performance across repeated tests). Subjects in Experiment 1 studied a list of words using either imaginal or semantic elaboration strategies and then received three successive tests. Different groups of subjects received either free recall, four-alternative forced-choice recognition, or yes/no recognition tests. Reliable hypermnesia was found only in the recall conditions, with the recognition conditions showing either no change in performance levels across tests (forced-choice tests) or significant forgetting (yes/no tests). In Experiment 2, subjects studied a list of words, and encoding was manipulated using three orienting tasks. Once again, hypermnesia was found with the recall tests but not with the forced choice recognition tests. Finding hypermnesia in recall but not in recognition indicates that retrieval processes in recall play a major role in producing hypermnesia. Also, the finding that the magnitude of the recall hypermnesias increased with an increase in total cumulative recall levels across study conditions suggests that cumulative recall levels are an important factor in determining the presence or absence of recall hypermnesia.     

Exploring the false recognition of category exemplars: Effects of divided attention and explicit generation

Two experiments used the category repetition procedure (Dewhurst & Anderson, 1999) to test the hypothesis that false remember (R) responses occur because participants generate associates to items presented at study. Participants in Experiment 1 studied the categorised lists either with full attention or whilst performing one of two secondary tasks (articulatory suppression or random number generation). Both secondary tasks led to a reduction in the number of false R responses, with random number generation producing the greater effect. Experiment 2 manipulated the presentation duration of study items and the instructions given to participants. The numbers of false R responses were not influenced by presentation duration, but increased when participants were explicitly instructed to make associations to study items. The findings support the view that false R responses are caused by the activation of semantic associates at encoding.     

Mathematics anxiety affects counting but not subitizing during visual enumeration

Individuals with mathematics anxiety have been found to differ from their non-anxious peers on measures of higher-level mathematical processes, but not simple arithmetic. The current paper examines differences between mathematics anxious and non-mathematics anxious individuals in more basic numerical processing using a visual enumeration task. This task allows for the assessment of two systems of basic number processing: subitizing and counting. Mathematics anxious individuals, relative to non-mathematics anxious individuals, showed a deficit in the counting but not in the subitizing range. Furthermore, working memory was found to mediate this group difference. These findings demonstrate that the problems associated with mathematics anxiety exist at a level more basic than would be predicted from the extant literature.     

Word imagery but not age of acquisition affects episodic memory

Evidence is presented from two experiments and from a reanalysis of data published by Christian, Bickley, Tarka, and Clayton (1978) that the chronological age at which a word is acquired does not affect free recall or recognition memory. Morris’s (1981) report, that late acquired words are better recalled than early acquired words, was not replicated and appears to be attributable to a difference in the emotionality value of his lists. Although the data are consistent with an interpretation in terms of semantic, but not episodic, memory tasks’ being sensitive to word age of acquisition, it is suggested that a more fine-grained analysis is necessary.     

Extent of food restriction affects probability but not delay-based decision-making

Rodent studies on decision-making often use food rewards and food-restrict subjects in order to motivate performance. However, food restriction has widespread effects on brain and behavior, which depend on factors including extent of restriction and feeding schedule. These factors are well recognized for their effects on motivation, but may also cause effects on decision-making independent of motivation. We examined how the degree of weight-based food restriction in rats influenced decision-making on the probability and delay discounting tasks. Additionally, we examined how the method of food restriction (consistent amount vs. time constrained feeding schedule) influenced decision-making. Our results showed that the degree of weight-based food restriction significantly altered probability, but not delay discounting, and that these effects were not entirely explainable by differences in motivation. Additionally, the method of food restriction did not significantly influence discounting when animals were within the same range of weight-based restriction. Together, our findings suggest that the degree of food restriction may modulate the neural circuitry responsible for selective aspects of decision-making related to probability. Further, these data support the need for tight control and reporting of weight and feeding in studies relying on food restriction, and suggest that the effects of food restriction may be broader than previously considered.