Category Exemplars Research Articles

Autobiographical Memory Fluency Reductions in Cognitively Unimpaired Middle-Aged and Older Adults at Increased Risk for Alzheimer's Disease Dementia.

Recent research has revealed that cognitively unimpaired older adults who are at higher risk for developing Alzheimer's disease (AD) dementia often exhibit subtle cognitive alterations in their neuropsychological profiles. Emerging evidence suggests that autobiographical memory, which is memory for personal events and knowledge, may be sensitive to early AD-related cognitive alterations. In the present study, we investigated whether the rapid generation of autobiographical memory category exemplars, a retrieval process that taxes the neural network that is vulnerable to early AD, is compromised in cognitively unimpaired middle-aged and older carriers of the e4 allele of the apolipoprotein E gene (APOE4), which increases risk for AD dementia. In addition to standard neuropsychological tests, we administered a fluency task that requires generating exemplars for two types of autobiographical memory, namely episodic memories and personal semantics, to a group of cognitively unimpaired middle-aged and older adults (n = 45) enriched with APOE4 carriers (n = 20). While no APOE4 deficits were found on standard neuropsychological tests, episodic and personal semantic exemplar generation was reduced in the APOE4 group. Autobiographical memory aberrations associated with a higher risk for AD are evident in fluency and affect both episodic memory and personal semantics.

Trait anxiety is associated with reduced typicality asymmetry in fear generalization

In fear conditioning, training with typical category exemplars has been shown to promote fear generalization to novel exemplars of the same category, whereas training with atypical category exemplars supports limited if any generalization to other category members, amounting to a typicality asymmetry in fear generalization. The present study sought to examine how trait anxiety bears on typicality asymmetry in fear generalization. Participants in one condition were presented with typical exemplars during fear acquisition and atypical exemplars of the same category in the subsequent generalization test (typical condition), whereas in the other group, atypical and typical exemplars were presented during fear acquisition and generalization test, respectively (atypical condition). We observed a typicality asymmetry in fear generalization in self-reported expectancy ratings in low trait anxious individuals only. High trait anxious individuals showed a similar degree of fear generalization in both conditions. The current results help illuminate why some individuals are at risk for exhibiting broad fear generalization after exposure to an aversive event.

Individual differences among deep neural network models

Deep neural networks (DNNs) excel at visual recognition tasks and are increasingly used as a modeling framework for neural computations in the primate brain. Just like individual brains, each DNN has a unique connectivity and representational profile. Here, we investigate individual differences among DNN instances that arise from varying only the random initialization of the network weights. Using tools typically employed in systems neuroscience, we show that this minimal change in initial conditions prior to training leads to substantial differences in intermediate and higher-level network representations despite similar network-level classification performance. We locate the origins of the effects in an under-constrained alignment of category exemplars, rather than misaligned category centroids. These results call into question the common practice of using single networks to derive insights into neural information processing and rather suggest that computational neuroscientists working with DNNs may need to base their inferences on groups of multiple network instances.

A daytime nap combined with nighttime sleep promotes learning in toddlers

Napping after learning promotes consolidation of new information during infancy. Yet, whether naps play a similar role during toddlerhood, a stage when many children are beginning to transition away from napping, is less clear. In Experiment 1, we examined whether napping after learning promotes generalization of novel category exemplars 24 h later. Young children (N = 54, age range = 29–36 months) viewed three category exemplars in different contexts from each of three categories and remained awake (No-Nap condition) or napped (Nap condition) after encoding and were then tested 24 h later. Children who napped after learning showed superior generalization 24 h later relative to children who did not nap. In a Nap-Control condition tested 4 h after awakening from a nap, children performed at the same low level as in the No-Nap condition, indicating that generalization stemmed from an additional period of nighttime sleep and not simply from a nap or increased time. In Experiment 2, we examined whether nighttime sleep is sufficient for generalization if it occurs soon after learning. An additional group of children (N = 18) learned before bedtime and were tested 4 h after waking up the next day. Children did not generalize as well as those who had a nap combined with subsequent nighttime sleep. These findings suggest that naps, when combined with a period of nighttime sleep, might help toddlers to retain newly learned information and lead to delayed benefits in generalization.

The influence of reward magnitude on stimulus memory and stimulus generalization in categorization decisions.

Reward magnitude is a central concept in most theories of preferential decision making and learning. However, it is unknown whether variable rewards also influence cognitive processes when learning how to make accurate decisions (e.g., sorting healthy and unhealthy food differing in appeal). To test this, we conducted 3 studies. Participants learned to classify objects with 3 feature dimensions into two categories before solving a transfer task with novel objects. During learning, we rewarded all correct decisions, but specific category exemplars yielded a 10 times higher reward (high vs. low). Counterintuitively, categorization performance did not increase for high-reward stimuli, compared with an equal-reward baseline condition. Instead, performance decreased reliably for low-reward stimuli. To analyze the influence of reward magnitude on category generalization, we implemented an exemplar-categorization model and a cue-weighting model using a Bayesian modeling approach. We tested whether reward magnitude affects (a) the availability of exemplars in memory, (b) their psychological similarity to the stimulus, or (c) attention to stimulus features. In all studies, the evidence favored the hypothesis that reward magnitude affects the similarity gradients of high-reward exemplars compared with the equal-reward baseline. The results from additional reward-judgment tasks (Studies 2 and 3) strongly suggest that the cognitive processes of reward-value generalization parallel those of category generalization. Overall, the studies provide insights highlighting the need for integrating reward- and category-learning theories. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Category norms with a cross-sectional sample of adults in the United States: Consideration of cohort, age, and historical effects on semantic categories.

This paper describes normative data for newly collected exemplar responses to 70 semantic categories described in previous norming studies (Battig & Montague, Journal of Experimental Psychology, 80(3, pt.2): 1-46, 1969; Van Overschelde, Rawson, & Dunlosky, Journal of Memory and Language, 50(3): 289-335, 2004; Yoon et al., Psychology and Aging, 19(3), 379-393, 2004). These categories were presented to 246 young (18-39 years), middle (40-59 years), and older (60 years and older) English-speaking adults living in the United States who were asked to generate as many category exemplars as possible for each of the 70 categories. In order to understand differences in normative responses, we analyzed these responses a) between age groups within the current sample and b) in comparison to three previously published sets of norms. Experimental studies using such norms typically assume invariance of normative likelihoods across age and historical time. We replicate previous findings such that exemplar frequency correlations suggest moderate stability in generated category members between age groups and cohorts for many, but not all, categories. Further, analyses of rank-order correlations highlight that the traditional measure of typicality may not capture all aspects of typicality, namely that for some categories there is high consistency in the frequency of exemplars across age groups and/or norms, but the ordering of those exemplars differs significantly. We include a cluster analysis to aid in grouping categories based on relative stability across time, cohort, and age groups. These results emphasize the importance of maintaining and updating age-differentiated category norms.

Effects of Chinese word structure on object categorization in Chinese–English bilinguals

ABSTRACTWe investigated how verbal labels affect object categorization in bilinguals. In English, most nouns do not provide linguistic clues to their categories (an exception issunflower), whereas in Chinese, some nouns provide category information morphologically (e.g., 鸵鸟-ostrichand 知更鸟-robinhave the morpheme鸟-birdin their Chinese names), while some nouns do not (e.g., 企鹅-penguinand 鸽子-pigeon). We examined the effect of Chinese word structure on bilinguals’ categorization processes in two ERP experiments. Chinese–English bilinguals and English monolinguals judged the membership of atypical (e.g.,ostrich,penguin) vs. typical (e.g.,robin,pigeon) pictorial (Experiment 1) and English word (Experiment 2) exemplars of categories (e.g.,bird). English monolinguals showed typicality effects in RT data, and in the N300 and N400 of ERP data, regardless of whether the object name had a category cue in Chinese. In contrast, Chinese–English bilinguals showed a larger typicality effect for objects without category cues in their name than objects with cues, even when they were tested in English. These results demonstrate that linguistic information in bilinguals’ L1 has an effect on their L2 categorization processes. The findings are explained using the label-feedback hypothesis.

Exemplar learning reveals the representational origins of expert category perception

Irrespective of whether one has substantial perceptual expertise for a class of stimuli, an observer invariably encounters novel exemplars from this class. To understand how novel exemplars are represented, we examined the extent to which previous experience with a category constrains the acquisition and nature of representation of subsequent exemplars from that category. Participants completed a perceptual training paradigm with either novel other-race faces (category of experience) or novel computer-generated objects (YUFOs) that included pairwise similarity ratings at the beginning, middle, and end of training, and a 20-d visual search training task on a subset of category exemplars. Analyses of pairwise similarity ratings revealed multiple dissociations between the representational spaces for those learning faces and those learning YUFOs. First, representational distance changes were more selective for faces than YUFOs; trained faces exhibited greater magnitude in representational distance change relative to untrained faces, whereas this trained-untrained distance change was much smaller for YUFOs. Second, there was a difference in where the representational distance changes were observed; for faces, representations that were closer together before training exhibited a greater distance change relative to those that were farther apart before training. For YUFOs, however, the distance changes occurred more uniformly across representational space. Last, there was a decrease in dimensionality of the representational space after training on YUFOs, but not after training on faces. Together, these findings demonstrate how previous category experience governs representational patterns of exemplar learning as well as the underlying dimensionality of the representational space.

The way in which foreign words are learned determines their use in isolation and within sentences.

We compared 2 learning methods for the acquisition of vocabulary in a second language (L2). In addition, the use of the new L2 words was evaluated both in isolation and within sentences. In the semantic method, L2 words and pictures denoting their meanings were presented and participants learned by practicing a semantic categorization task (to indicate whether new words were exemplars of semantic categories). In the lexical methods, individuals received L1-L2 word pairs and they performed a letter-monitoring task (to indicate whether L1-L2 words contained a grapheme). After training, compared with the lexical learning group, the semantic learning group showed: (a) no cost between training sessions, (b) better performance in out-of-context tasks (e.g., picture naming), and (c) an efficient processing of L2 words in sentences. The pattern of outcomes shows the advantage of semantic learning for the acquisition and the use of L2 words in isolation and within sentences. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Acquisition and generalization of cough trigger beliefs in allergic rhinitis.

In allergic conditions, trigger identification is often inaccurate, and may be influenced by pre-existing beliefs. In this study, we investigated the acquisition and generalization of symptom trigger beliefs in individuals with allergic rhinitis (n = 24) and control participants (n = 24). In a lab-based trigger acquisition task, unique exemplars of two trigger categories were either paired with saline inhalation (CS- category) or citric acid inhalation (CS+ category). The next day, we tested recognition and symptom expectancy for CS category exemplars and exemplars of novel trigger categories. Participants acquired differential symptom expectancies for CS+ compared to CS- exemplars, with faster acquisition in participants with rhinitis. Differential symptom expectancies persisted the next day, and generalized to novel trigger categories, with stronger generalization in rhinitis vs. control participants. These patterns of acquisition and generalization suggest that overgeneralization of trigger beliefs may complicate trigger identification in participants with allergic conditions.

The effects of aversive-to-appetitive counterconditioning on implicit and explicit fear memory.

Counterconditioning (CC) is a form of retroactive interference that inhibits expression of learned behavior. But similar to extinction, CC can be a fairly weak and impermanent form of interference, and the original behavior is prone to relapse. Research on CC is limited, especially in humans, but prior studies suggest it is more effective than extinction at modifying some behaviors (e.g., preference or valence ratings) than others (e.g., physiological arousal). Here, we used a within-subjects design to compare the effects of aversive-to-appetitive CC versus standard extinction on two separate tests of long-term memory in human adults: implicit physiological arousal and explicit episodic memory. Participants underwent Pavlovian fear conditioning to two semantic categories (animals, tools) paired with an electric shock. Conditioned stimuli (i.e., category exemplars) from one category were then extinguished, while stimuli from the other category were paired with a positive outcome. Participants returned 24-h later for a test of skin conductance responses (SCR) to the conditioned exemplars, as well as a surprise recognition memory test for stimuli encoded the previous day. Results showed reduced SCRs at a test for unique stimuli from a category that had undergone CC, relative to stimuli from a category that had undergone standard extinction. Additionally, participants selectively remembered more stimuli encoded during CC than extinction. These results provide new evidence that aversive-to-appetitive CC, as compared to extinction, strengthens memory for items directly associated with a positive outcome, which may provide stronger retrieval competition against a fear memory at test to help diminish fear relapse.

Effects of formant proximity and stimulus prototypicality on the neural discrimination of vowels: Evidence from the auditory frequency-following response

Cross-language speech perception experiments indicate that for many vowel contrasts, discrimination is easier when the same pair of vowels is presented in one direction compared to the reverse direction. According to one account, these directional asymmetries reflect a universal bias favoring “focal” vowels (i.e., vowels with prominent spectral peaks formed by the convergence of adjacent formants). An alternative account is that such effects reflect an experience-dependent bias favoring prototypical exemplars of native-language vowel categories. Here, we tested the predictions of these accounts by recording the auditory frequency-following response in English-speaking listeners to two synthetic variants of the vowel /u/ that differed in the proximity of their first and second formants and prototypicality, with stimuli arranged in oddball and reversed-oddball blocks. Participants showed evidence of neural discrimination when the more-focal/less-prototypic /u/ served as the deviant stimulus, but not when the less-focal/more-prototypic /u/ served as the deviant, consistent with the focalization account.

The congruent, the incongruent, and the unexpected: Event-related potentials unveil the processes involved in schematic encoding

Learning is most effective when new information can be related to a preexisting knowledge structure or schema. In the present study, event-related potentials (ERPs) were used to investigate the temporal dynamics of the processes by which activated schemata support the encoding of schema-congruent information. Participants learned category exemplar words that were either semantically congruent or incongruent with a preceding category cue phrase. Congruent words were composed of expected (high typicality, HT) and unexpected (low typicality, LT) category exemplars. On the next day, recognition memory for the exemplars and the category cues they were presented with was tested. Semantically related lures were used in order to ascertain that memory judgements were based on episodic memory for specific category exemplars. Generally, congruent (HT and LT) exemplars were remembered better than incongruent exemplars. ERPs recorded during the encoding of the exemplar words were compared for subsequently remembered and forgotten items. Subsequent memory effects (SME) emerged in the N400 time window at frontal electrodes and did not differ between congruent and incongruent exemplars. In the same epoch, an SME with a parietal distribution was specific for congruent exemplars, suggesting that activated schemata strengthened memory for congruent exemplars by supporting the encoding of item-specific details. Subsequently remembered LT exemplars were associated with a late frontal positivity that is assumed to reflect expectancy mismatch-related processing such as the contextual integration of an unexpected word by the suppression of strongly expected words. A correlation analysis revealed that the greater the involvement of the processes reflected by the frontal positivity, the lower the level of false positive memory responses in the test phase one day later. These results suggest that the contextual integration of schema-congruent but unexpected events involves a weakening of the representations of semantically related, but unstudied items in memory and by this benefits subsequent memory.

Divided attention and the encoding effects of retrieval.

Retrieving from memory both reveals as well as modifies memory. It is important to understand how these encoding effects of retrieval differ from other forms of encoding. One possible difference relates to attention: divided attention is well known to disrupt memory encoding but typically has much less impact on memory retrieval. However, less is known about the relative attentional demands of the encoding consequences of retrieval. The current experiments examined retrieval-based encoding using free recall, a retrieval task purported to require substantial attentional resources. In three experiments, participants studied common category exemplars (Phase 1), restudied or freely recalled the exemplars (Phase 2), and then took a final free-recall test (Phase 3). Phase 2 occurred under full attention (FA) or divided attention (DA). In all three experiments, the negative effect of DA on final recall was significant in the restudy but not retrieval condition. The pattern persisted with short (Experiment 1) or long study lists (Experiment 2), requiring lesser or greater retrieval effort, and with multiple Phase 2 tests, permitting the development of more elaborate retrieval strategies (Experiment 3). The encoding effects of retrieval appear resilient to distraction, even using a memory task that is more effortful and easily disrupted by DA (i.e., free recall). In addition, these results are inconsistent with elaboration and effort accounts of retrieval-based learning.

Optimal distinctiveness, strategic categorization, and product market entry on the Google Play app platform

Research SummaryNew entrants often face uncertainty regarding how to optimally position themselves within product markets. We suggest that new entrants can use two important schemas to strategically categorize themselves to gain a competitive advantage in platform markets: category exemplars and category prototypes. Using a unique dataset of more than 83,000 new Google Play developers and more than 139,000 apps, we find that the optimally distinct entry point is at a high level of exemplar similarity and a low level of prototype similarity. We find that greater alignment of an entrant with the prototype corresponds to a weaker benefit of exemplar similarity. These findings have important implications for understanding competitive dynamics within product markets, strategic positioning at entry, and the interdependence of strategic categorization decisions. Managerial SummaryEntrepreneurial startups often find it difficult to know how to optimally position their products among a large number of rivals in highly competitive platform markets. Our study suggests that these startups can draw on two reference points to help determine the optimal positioning for their products: category exemplars and category prototypes. Exemplars include the most successful products in a market category while prototypes represent the most common products in a category. Drawing on a large dataset obtained from the Google Play app store, we find that developers can substantially increase the installs of their first app by crafting an app text description that is as similar as possible to the description of a category exemplar and as different as possible from the category's prototypical description.

Cognitive reappraisal during unpleasant picture processing: Subjective self-report and peripheral physiology.

Increased attention among the research community in exploring underlying mechanisms of emotion regulation has prompted a growth of experimental works in this field. Empirical studies have mainly focused on self-reports, brain imaging, and electrophysiological measures, with only a few works exploring peripheral physiology. Additionally, most of such studies have not considered the specific stimuli content, even though prior literature has shown relevant differences in psychophysiological and subjective responses depending on picture categories. The current study assessed several peripheral correlates (startle amplitude, electrodermal changes, heart rate) of emotion regulation processes in a sample of 122 healthy participants. The task consisted of voluntary reappraisal of negative emotions prompted by unpleasant pictures (threat to others and victims), compared to a nonregulation control condition (looking at exemplars of the same categories and household objects). Results showed an effect of emotion regulation instructions in all psychophysiological and subjective measures. In peripheral physiology, greater responses were observed specifically when increasing negative emotions, concurring with previous research. Regarding specific content, our findings evidence a similar emotion regulation pattern, independently of the unpleasant category, suggesting a plausible effect of cognitive variables (such as cognitive effort) during voluntary reappraisal for both categories.

Role of the striatum in incidental learning of sound categories

Humans are born as "universal listeners" without a bias toward any particular language. However, over the first year of life, infants' perception is shaped by learning native speech categories. Acoustically different sounds-such as the same word produced by different speakers-come to be treated as functionally equivalent. In natural environments, these categories often emerge incidentally without overt categorization or explicit feedback. However, the neural substrates of category learning have been investigated almost exclusively using overt categorization tasks with explicit feedback about categorization decisions. Here, we examined whether the striatum, previously implicated in category learning, contributes to incidental acquisition of sound categories. In the fMRI scanner, participants played a videogame in which sound category exemplars aligned with game actions and events, allowing sound categories to incidentally support successful game play. An experimental group heard nonspeech sound exemplars drawn from coherent category spaces, whereas a control group heard acoustically similar sounds drawn from a less structured space. Although the groups exhibited similar in-game performance, generalization of sound category learning and activation of the posterior striatum were significantly greater in the experimental than control group. Moreover, the experimental group showed brain-behavior relationships related to the generalization of all categories, while in the control group these relationships were restricted to the categories with structured sound distributions. Together, these results demonstrate that the striatum, through its interactions with the left superior temporal sulcus, contributes to incidental acquisition of sound category representations emerging from naturalistic learning environments.

The role of category density in pigeons' tracking of relevant information.

Prior categorization studies have shown that pigeons reliably track features that are relevant to category discrimination. In these studies, category exemplars contained two relevant and two irrelevant features; therefore, category density (specifically, the relevant to irrelevant information ratio) was relatively high. Here, we manipulated category density both between and within subjects by keeping constant the amount of relevant information (one feature) and varying the amount of irrelevant information (one or three features). One group of pigeons started with low-density training, then proceeded to high-density training, and finally returned to low-density training (Low-High-Low); a second group of pigeons started with high-density training and then proceeded to low-density training (High-Low). The statistical density of the category exemplars had a large effect on pigeons' performance. Training with high-density exemplars greatly benefitted category learning. Accuracy rose faster and to a higher level with high-density training than with low-density training; the percentage of relevant pecks showed a very similar pattern. In addition, high-density training (in the Low-High-Low group) led to an increase in performance on the more difficult low-density task, an observation reminiscent of the easy-to-hard effect. These results illuminate factors affecting pigeons' accuracy and tracking of relevant information in visual categorization.

When Object Color Is a Red Herring: Extraneous Perceptual Information Hinders Word Learning via Referent Selection

Learning words from ambiguous naming events is difficult. In such situations, children struggle with not attending to task irrelevant information when learning object names. This paper reduces the problem space of learning names for object categories by holding color constant between the target and other extraneous objects. We examine how this influences two types of word learning (retention and generalization) in both 30-month-old children (Experiment 1) and the iCub humanoid robot (Experiment 2). Overall, all children and iCub performed well on the retention trials, but they were only able to generalize the novel names to new exemplars of the target categories if the objects were originally encountered in sets with objects of the same colors, not if the objects were originally encountered in sets with objects of different colors. These data demonstrate that less information presented during the learning phase narrows the problem space and leads to better word learning success for both children and iCub. Findings are discussed in terms of cognitive load and desirable difficulties.

False memories produced by tentatively organized categorical representations: The Deese–Roediger–McDermott (DRM) paradigm using lists of ad hoc category exemplars

False memories produced by tentatively organized categorical representations: The Deese–Roediger–McDermott (DRM) paradigm using lists of ad hoc category exemplars