Diversity during training enhances detection of novel stimuli

This research demonstrates that when individuals are expected to detect novel targets, they will be best prepared when trained with diverse categories. Participants were trained in a simulated luggage screening task in one of three conditions of diversity: high (participants searched for dangerous objects belonging to five different categories); low (participants searched for targets belonging to one of the five categories); and no training (control condition). After training, all participants were asked to look for the same novel dangerous objects in the bags. Results show that, during training, the low diversity condition resulted in highest hit rates and fastest response times. In contrast, after training, results were reversed: participants that trained in a high diversity condition were most effective at detecting novel targets. Those with no training at all were equally poor at detecting novel targets as those that trained in a low diversity condition.     

Effects of category diversity on learning,memory, and generalization

In this study, we examined the effect of within-category diversity on people's ability to learn perceptual categories, their inclination to generalize categories to novel items, and their ability to distinguish new items from old. After learning to distinguish a control category from an experimental category that was either clustered or diverse, participants performed a test of category generalization or old-new recognition. Diversity made learning more difficult, increased generalization to novel items outside the range of training items, and made it difficult to distinguish such novel items from familiar ones. Regression analyses using the generalized context model suggested that the results could be explained in terms of similarities between old and new items combined with a rescaling of the similarity space that varied according to the diversity of the training items. Participants who learned the diverse category were less sensitive to psychological distance than were the participants who learned a more clustered category.     

Contextual memory and skill transfer in category search

In three experiments, we examined transfer and contextual memory in a category search task. Each experiment included two phases (training and test), during which participants searched through category and exemplar menus for targets. In Experiment 1, the targets were from one of two domains during training (grocery store or department store); the domain was either the same or changed at test. Also, the categories were organized in one of two ways (alphabetically or semantically); the organization either remained the same or changed at test. In Experiments 2 and 3, domain and organization were held constant; however, categories or exemplars were the same, partially replaced, or entirely replaced across phases in order to simulate the dynamic nature of category search in everyday situations. Transfer occurred at test when the category organization or domain was maintained and when the categories or exemplars matched (partially or entirely) those at training. These results demonstrate that transfer is facilitated by overlap in training and testing contexts.     

The Role of Incentive Framing on Training and Transfer of Learning in a Visual Threat Detection Task

We examined the effects of different incentives on skill acquisition and transfer during threat detection in airline luggage screening. The incentives were presented within positive (gains) or negative (losses) frames, and points were given or taken away accordingly during training (with familiar targets) and transfer (to novel targets). During training, incentives exerted a more beneficial effect on skill acquisition than training without incentives. During transfer, incentives benefitted performance largely when presented as losses or penalties. Incentives framed as gains primed participants to say ‘yes’ more often leading to a high ratio of false positives; however, incentives framed as losses lead participants to become more selective in their ‘yes’ responses leading to a lower number of false positives but a comparable probability of correct detections. Interestingly, participants that received no training outperformed participants that received incentive‐based training, suggesting that incentives actually constrained rather than helped transfer of learning in this study. Copyright © 2011 John Wiley & Sons, Ltd.     

Discrimination and categorization of photographs of natural objects by chimpanzees (Pan troglodytes)

Two experiments assessed the ability of four adult female chimpanzees to categorize natural objects. Chimpanzees were initially trained to match different color photographs of familiar objects from four possible categories. In training, all the comparison stimuli were from the same category in one condition, and from different categories in another condition. For all subjects, training performance was consistently better for the "different category" than for the "same category" trials. Probe trials were shown after training. In probe trials, the sample and positive comparison stimuli were different items from the same category, and the foils were selected from among the three other test categories. Individual performance was above chance in probe trials, suggesting that categorization by chimpanzees may transcend perceptual resemblance. These results were later replicated with novel stimulus items from the same four categories (experiment 2). Altogether, this research demonstrates that chimpanzees grouped perceptually different exemplars within the same category, and further suggests that these animals formed conceptual representations of the categories. Accepted after revision: 10 August 2001 Electronic Publication     

Tracking the emergence of memories: A category-learning paradigm to explore schema-driven recognition

Previous research has shown that prior knowledge structures or schemas affect recognition memory. However, since the acquisition of schemas occurs over prolonged periods of time, few paradigms allow the direct manipulation of schema acquisition to study their effect on memory performance. Recently, a number of parallelisms in recognition memory between studies involving schemas and studies involving category learning have been identified. The current paper capitalizes on these findings and offers a novel experimental paradigm that allows manipulation of category learning between individuals to study the effects of schema acquisition on recognition. First, participants learn to categorize computer-generated items whose category-inclusion criteria differ between participants. Next, participants study items that belong to either the learned category, the non-learned category, both, or neither. Finally, participants receive a recognition test that includes old and new items, either from the learned, the non-learned, or neither category. Using variations on this paradigm, four experiments were conducted. The results from the first three studies suggest that learning a category increases hit rates for old category-consistent items and false alarm rates for new category-consistent lures. Absent the category learning, no such effects are evident, even when participants are exposed to the same learning trials as those who learned the categories. The results from the fourth experiment suggest that, at least for false alarm rates, the effects of category learning are not solely attributable to frequency of occurrence of category-consistent items during learning. Implications for recognition memory as well as advantages of the proposed paradigm are discussed.     

The Impact of Target Base Rate on Training and Transfer of Learning in Airline Luggage Screening: An Examination of Three Base Rate Scenarios

We examined the extent to which transfer of training is impacted by target probability and physical similarity of training and transfer stimuli. Participants performed a luggage screening task where they trained on three base rates of weapon presence as follows: 100%, 50% and 20%; at transfer, participants detected the same weapons (Study 1) or novel weapons (Studies 2 and 3) at a base rate of 20%. In Study 3, we modified training such that all participants observed the same absolute number of weapons (n = 100) across base rate conditions. In Study 1, different base rates did not significantly impact transfer. In Study 2, 100% base rates helped hit rates at transfer but increased false alarms via liberal shifts in decision criteria and slowed detection times. Study 3 revealed no effect of base rates on transfer hit rates; however, training on 100% base rates still led to liberal responding and inflated false alarms. Copyright © 2013 John Wiley & Sons, Ltd.     

短期习得的语言范畴使成人大脑右半球颜色范畴知觉转为左半球颜色范畴知觉

本研究探讨了色词与颜色重组训练能否让被试习得与真实情境相似的色词与颜色范畴联结, 并引起相应的偏侧化颜色范畴知觉, 从而进一步揭示语言编码对颜色范畴知觉的影响。采用六种蓝色作为材料。B1与B2为先前研究的两种蓝色。B11和B12, B21和B22分别为使B1, B2变浅和变深所得, 四者是连续的蓝色。训练被试分别用“duān”和“kěn”命名B1和B2。由于被试可能习得色词与颜色范畴的联结, 因此B12与B21为可能变范畴间颜色, B11和B12, B21和B22为可能变范畴内颜色。训练前后分别让被试完成一个视觉搜索测验。结果发现：前测中可能变范畴间颜色的辨别优于可能变范畴内颜色, 且在左视野呈现时更显著; 后测中可能变范畴间颜色的辨别同样优于可能变范畴内颜色, 但在右视野呈现时更显著。这提示：(1)人们在知觉同一语言范畴的不同颜色时可能会区分深浅范畴, 并因此引发右半球颜色范畴知觉; (2)短期习得的语言范畴能引起偏左半球颜色范畴知觉, 且使右半球颜色范畴知觉转为左半球颜色范畴知觉; (3)被试在训练中习得了色词与颜色范畴的联结; (4)范畴学习可以在仅学习一个样例的条件下自动发生。     

Neural correlates of acquired color category effects

Category training can induce category effects, whereby color discrimination of stimuli spanning a newly learned category boundary is enhanced relative to equivalently spaced stimuli from within the newly learned category (e.g., categorical perception). However, the underlying mechanisms of these acquired category effects are not fully understood. In the current study, Event-Related Potentials (ERPs) were recorded during a visual oddball task where standard and deviant colored stimuli from the same or different novel categories were presented. ERPs were recorded for a test group who were trained on these novel categories, and for an untrained control group. Category effects were only found for the test group on the trained region of color space, and only occurred during post-perceptual stages of processing. These findings provide new evidence for the involvement of cognitive mechanisms in acquired category effects and suggest that category effects of this kind can exist independent of early perceptual processes.     

Failure to find evidence of stimulus generalization within pictorial categories in pigeons

Pigeons' key pecks were reinforced in the presence of pictures from one of two categories, cats or cars. A single picture associated with reinforcement was used in Experiment 1, and 20 pictures from the same category were associated with reinforcement in Experiment 2. Pigeons then were presented with novel test pictures from the training category and from the other, previously unseen, category. During Session 1 of testing, pigeons pecked no more often at pictures from the reinforced category than at pictures from the previously unseen category. When pigeons were trained with pictures associated with reinforcement or its absence from different categories in Experiment 3, differential responding to novel pictures from different categories appeared during Session 1. These findings argue against a process of automatic stimulus generalization within natural categories and in favor of the position that category distinctions are not made until members of at least two categories are compared with one another.     

Exploring specificity of speeded aiming movements: Examining different measures of transfer

Participants were trained and tested to move a mouse cursor from a start position to targets on a circular display in a perceptual-motor reversal condition, with horizontal, but not vertical, reversals. During training, some participants (experimental) moved to two targets either along a single diagonal axis (D1) or along both axes (D2). For D2, return movements from the targets were in the same direction as instructed movements to unpracticed targets. Others (control) trained on all targets. Testing always involved all targets. At test, movement times (to reach the target after leaving the start position) were shorter on trained than on untrained targets, especially for the D1 condition, documenting training specificity. However, movement times in the experimental conditions to new targets during testing were shorter than those in the control condition during training, documenting transfer of learning, with more transfer for D2 than for D1. Initiation times (to leave the start position after target onset) showed no transfer. The results provide evidence that specificity and transfer are not mutually exclusive and depend on the measure used to assess performance.     

习得的语言范畴影响颜色知觉的机制:来自ERP的证据

本研究以两个实验探讨了习得的语言范畴影响颜色知觉的机制.实验1让被试接受短期“色-词”重组训练,使原先范畴内的两种颜色变为范畴间的颜色,训练前后完成视觉搜索任务.反应时结果显示,在训练后,与训练的两种颜色近似的另外两种颜色的知觉表现出边缘显著的偏侧化颜色范畴效应.实验2让被试接受与实验1相同的训练后,完成视觉Oddball任务.ERP结果显示,在训练后,与训练的两种颜色近似的另外两种颜色的偏差刺激在早期知觉阶段就表现出偏侧化vMMN效应.这些结果表明:习得的语言范畴能影响早期的、注意前的颜色知觉机能,且这一影响过程可以在短期内完成;习得的语言范畴会影响颜色知觉范畴,而非仅影响特定颜色点的知觉机能.     

Improved classification of mammograms following idealized training

People often make decisions by stochastically retrieving a small set of relevant memories. This limited retrieval implies that human performance can be improved by training on idealized category distributions (Giguère & Love, 2013). Here, we evaluate whether the benefits of idealized training extend to categorization of real-world stimuli, namely classifying mammograms as normal or tumorous. Participants in the idealized condition were trained exclusively on items that, according to a norming study, were relatively unambiguous. Participants in the actual condition were trained on a representative range of items. Despite being exclusively trained on easy items, idealized-condition participants were more accurate than those in the actual condition when tested on a range of item types. However, idealized participants experienced difficulties when test items were very dissimilar from training cases. The benefits of idealization, attributable to reducing noise arising from cognitive limitations in memory retrieval, suggest ways to improve real-world decision making.     

Specific-token effects in screening tasks: possible implications for aviation security

Screeners at airport security checkpoints perform an important categorization task in which they search for threat items in complex x-ray images. But little is known about how the processes of categorization stand up to visual complexity. The authors filled this research gap with screening tasks in which participants searched for members of target categories in visual displays. The authors found that when targets were sampled with replacement and repetition, participant screeners relied on recognizing familiar targets and had great difficulty using category-general knowledge. The authors observed a "heartbeat" in detection performance--it improved while test images repeated but dropped sharply when unfamiliar targets from the same categories appeared. This reliance on familiarity illuminates the processes of categorization under conditions of visual complexity and suggests limits on those processes. This reliance also has implications for the training and evaluation of screeners in the field.     

The development of category learning strategies: What makes the difference?

Category learning can be achieved by identifying common features among category members, distinctive features among non-members, or both. These processes are psychologically and computationally distinct, and may have implications for the acquisition of categories at different hierarchical levels. The present study examines an account of children’s difficulty in acquiring categories at the subordinate level grounded on these distinct comparison processes. Adults and children performed category learning tasks in which they were exposed either to pairs of objects from the same novel category or pairs of objects from different categories. The objects were designed so that for each category learning task, two features determined category membership whereas two other features were task irrelevant. In the learning stage participants compared pairs of objects noted to be either from the same category or from different categories. Object pairs were chosen so that the objective amount of information provided to the participants was identical in the two learning conditions. We found that when presented only with object pairs noted to be from the same category, young children (6 ? YO ? 9.5) learned the novel categories just as well as older children (10 ? YO ? 14) and adults. However, when presented only with object pairs known to be from different categories, unlike older children and adults, young children failed to learn the novel categories. We discuss cognitive and computational factors that may give rise to this comparison bias, as well as its expected outcomes.     

TRAINING GENERALIZED RECEPTIVE PREPOSITIONS IN RETARDED CHILDREN1

Three retarded children were trained, using prompting and reinforcement procedures, to respond correctly to three categories of prepositional requests: “put the___ next to the___”, “put the___under the___”, and “put the___on top of the___”. Training sessions were alternated with probe sessions throughout the study. During training, a child was trained to respond to one request (e.g., “put the doll next to the cup”); during probing, the child was tested for generalization of this training to untrained requests. Responses to untrained requests were never prompted nor reinforced. The results showed that, as requests from one category were trained, the children's responses to the untrained requests of that category became increasingly correct. As discriminations among two or more categories were trained, the children's responses to the untrained requests of those categories also became increasingly correct. Thus, the methods employed appear to be successful in training generalized receptive discrimination among prepositional categories and possibly can be utilized in training other generalized receptive language skills.     

Information about the logical structure of a category affects generalization

This paper considers whether information about the logical structure of a category affects how people generalize. We carried out three experiments with the following structure: participants were first presented with a set of training items, and were subsequently asked to decide whether new items belonged to the same category as the training items. Each experiment had two conditions that differed only in terms of the category label provided for the training items; different category labels conveyed different information about the logical structure of the category to which the training items were supposed to belong. In all cases, participants' generalization was greatly affected by such information. Our results suggest that people make the default assumption that category labels correspond to groupings of highly similar objects.     

Visual search and the collapse of categorization

Categorization researchers typically present single objects to be categorized. But real-world categorization often involves object recognition within complex scenes. It is unknown how the processes of categorization stand up to visual complexity or why they fail facing it. The authors filled this research gap by blending the categorization and visual-search paradigms into a visual-search and categorization task in which participants searched for members of target categories in complex displays. Participants have enormous difficulty in this task. Despite intensive and ongoing category training, they detect targets at near-chance levels unless displays are extremely simple or target categories extremely focused. These results, discussed from the perspectives of categorization and visual search, might illuminate societally important instances of visual search (e.g., diagnostic medical screening).     

The training and transfer of real-world perceptual expertise

A hallmark of perceptual expertise is that experts classify objects at a more specific, subordinate level of abstraction than novices. To what extent does subordinate-level learning contribute to the transfer of perceptual expertise to novel exemplars and novel categories? In this study, participants learned to classify 10 varieties of wading birds and 10 varieties of owls at either the subordinate, species (e.g., "great blue crown heron,"eastern screech owl") or the family ("wading bird,"owl") level of abstraction. During training, the amount of visual exposure was equated such that participants received an equal number of learning trials for wading birds and owls. Pre- and posttraining performance was measured in a same/different discrimination task in which participants judged whether pairs of bird stimuli belonged to the same or different species. Participants trained in species-level discrimination demonstrated greater transfer to novel exemplars and novel species categories than participants trained in family-level discrimination. These findings suggest that perceptual categorization, not perceptual exposure per se, is important for the development and generalization of visual expertise.     

Contrastive Constraints Guide Explanation‐Based Category Learning

This paper provides evidence for a contrastive account of explanation that is motivated by pragmatic theories that recognize the contribution that context makes to the interpretation of a prompt for explanation. This study replicates the primary findings of previous work in explanation‐based category learning (Williams & Lombrozo, 2010), extending that work by illustrating the critical role of the context in this type of learning. Participants interacted with items from two categories either by describing the items or explaining their category membership. We manipulated the feature overlap between the categories and examined both the explanations generated and acquired knowledge of the categories. Explanations for membership in a given category were influenced by the unprompted contrast category, indicating an important role for contrastive processing in the generation of explanations. The influence of the contrast category was similarly seen in the transfer performance of the participants.