Hemispheric processing asymmetries: implications for memory

Recent research has demonstrated that memory for words elicits left hemisphere activation, faces right hemisphere activation, and nameable objects bilateral activation. This pattern of results was attributed to dual coding of information, with the left hemisphere employing a verbal code and the right a nonverbal code. Nameable objects can be encoded either verbally or nonverbally and this accounts for their bilateral activation. We investigated this hypothesis in a callosotomy patient. Consistent with dual coding, the left hemisphere was superior to the right in memory for words, whereas the right was superior for faces. Contrary to prediction, performance on nameable pictures was not equivalent in the two hemispheres, but rather resulted in a right hemisphere superiority. In addition, memory for pictures was significantly better than for either words or faces. These findings suggest that the dual code hypothesis is an oversimplification of the processing capabilities of the two hemispheres.     

Viewpoint dependence and object discriminability

In an attempt to reconcile results of previous studies, several theorists have suggested that object recognition performance should range from viewpoint invariant to highly viewpoint dependent depending on how easy it is to differentiate the objects in a given recognition situation. The present study assessed recognition across depth rotations of a single general class of novel objects in three contexts that varied in difficulty. In an initial experiment, recognition in the context involving the most discriminable object differences was viewpoint invariant, but recognition in the least discriminable context and recognition in the intermediate context were equally viewpoint dependent. In a second experiment, utilizing gray-scale versions of the same stimuli, almost identical viewpoint-cost functions were obtained in all three contexts. These results suggest that differences in the geometry of stimulus objects, rather than task difficulty, lie at the heart of previously discrepant findings.     

Speech-like coding of pictures in short-term memory

Memory span for pictures of common objects and for the names of these objects was examined as a function of three speech-related variables. Both picture span and name span were found to be influenced by the phonological similarity (Experiment 1) and the length (Experiment 2) of the names, as well as by the subject’s engaging in “irrelevant” vocalization during item presentation (Experiment 3). Moreover, for each variable the effect was in the same direction and of comparable magnitude for the two types of items. Experiments 4-6 replicated these findings with the procedure modified such that the retention of order information was not required. It is concluded that under the present conditions, there is a substantial functional equivalence between short-term memory for readily nameable pictures and for words and that this equivalence may be thought of as due to mediation by a common, “speech-like” code.     

Selective learning of spatial configuration and object identity in visual search

To conduct an efficient visual search, visual attention must be guided to a target appropriately. Previous studies have suggested that attention can be quickly guided to a target when the spatial configurations of search objects or the object identities have been repeated. This phenomenon is termed contextual cuing. In this study, we investigated the effect of learning spatial configurations, object identities, and a combination of both configurations and identities on visual search. The results indicated that participants could learn the contexts of spatial configurations, but not of object identities, even when both configurations and identities were completely correlated (Experiment 1). On the other hand, when only object identities were repeated, an effect of identity learning could be observed (Experiment 2). Furthermore, an additive effect of configuration learning and identity learning was observed when, in some trials, each context was the relevant cue for predicting the target (Experiment 3). Participants could learn only the context that was associated with target location (Experiment 4). These findings indicate that when multiple contexts are redundant, contextual learning occurs selectively, depending on the predictability of the target location.     

The visual system supports online translation invariance for object identification

The ability to recognize the same image projected to different retinal locations is critical for visual object recognition in natural contexts. According to many theories, the translation invariance for objects extends only to trained retinal locations, so that a familiar object projected to a nontrained location should not be identified. In another approach, invariance is achieved “online,” such that learning to identify an object in one location immediately affords generalization to other locations. We trained participants to name novel objects at one retinal location using eyetracking technology and then tested their ability to name the same images presented at novel retinal locations. Across three experiments, we found robust generalization. These findings provide a strong constraint for theories of vision.     

Culture and the Interaction of Student Ethnicity with Reward Structure in Group Learning

This study tests the hypothesis that cultural differences in group orientation predict an interaction between the student variable—ethnicity—and a learning context variable—reward structure—on math performance after group learning. One hundred and thirty-two African-American and European-American female and male fourth and fifth grade students studied math estimation in one of three group learning contexts. The learning contexts operationalized were: intergroup competitive, interpersonally competitive, and communal-no reward. ANCOVA confirmed a predicted interaction of ethnicity with learning context on post study session performance. Although there was no difference overall, African-American and European-American students performed best in the aggregate in different contexts. Independent ratings of students' group-positive behaviors mirrored the two-way interaction between learning context and ethnicity. The findings suggest that important student variables interact with the variable elements of group learning and should be studied in greater detail. They also support Boykin's (1994) contention that the cultural context of learning is a critical mediator of children's achievement.     

Memory for dangers past: threat contexts produce more consistent learning than do non-threatening contexts

In earlier work we showed that individuals learn the spatial regularities within contexts and use this knowledge to guide detection of threatening targets embedded in these contexts. While it is highly adaptive for humans to use contextual learning to detect threats, it is equally adaptive for individuals to flexibly readjust behaviour when contexts once associated with threatening stimuli begin to be associated with benign stimuli, and vice versa. Here, we presented face targets varying in salience (threatening or non-threatening) in new or old spatial configurations (contexts) and changed the target salience (threatening to non-threatening and vice versa) halfway through the experiment to examine if contextual learning changes with the change in target salience. Detection of threatening targets was faster in old than new configurations and this learning persisted even after the target changed to non-threatening. However, the same pattern was not seen when the targets changed from non-threatening to threatening. Overall, our findings show that threat detection is driven not only by stimulus properties as theorised traditionally but also by the learning of contexts in which threatening stimuli appear, highlighting the importance of top-down factors in threat detection. Further, learning of contexts associated with threatening targets is robust and speeds detection of non-threatening targets subsequently presented in the same context.     

Learning in repeated visual search

Visual search (e.g., finding a specific object in an array of other objects) is performed most effectively when people are able to ignore distracting nontargets. In repeated search, however, incidental learning of object identities may facilitate performance. In three experiments, with over 1,100 participants, we examined the extent to which search could be facilitated by object memory and by memory for spatial layouts. Participants searched for new targets (real-world, nameable objects) embedded among repeated distractors. To make the task more challenging, some participants performed search for multiple targets, increasing demands on visual working memory (WM). Following search, memory for search distractors was assessed using a surprise two-alternative forced choice recognition memory test with semantically matched foils. Search performance was facilitated by distractor object learning and by spatial memory; it was most robust when object identity was consistently tied to spatial locations and weakest (or absent) when object identities were inconsistent across trials. Incidental memory for distractors was better among participants who searched under high WM load, relative to low WM load. These results were observed when visual search included exhaustive-search trials (Experiment 1) or when all trials were self-terminating (Experiment 2). In Experiment 3, stimulus exposure was equated across WM load groups by presenting objects in a single-object stream; recognition accuracy was similar to that in Experiments 1 and 2. Together, the results suggest that people incidentally generate memory for nontarget objects encountered during search and that such memory can facilitate search performance.     

阅读方式和学习次数对中文词汇的产生效应的影响

产生效应是指朗读单词的记忆成绩要好于默读单词的。目前存在特异观和强度观两种理论解释,特异观强调朗读的相对特殊性,强度观强调朗读单词的编码强度高于默读单词的。为了检验两种理论,本研究采用“学习-再认”的实验范式,将阅读方式分别设置为被试内和被试间变量,通过两项实验考察阅读方式和学习次数对中文词汇的产生效应的影响。实验1采用被试内设计考察阅读方式和学习次数对产生效应的影响。结果发现阅读方式和学习次数的主效应显著,二者的交互作用不显著。实验2将阅读方式设置为被试间变量,采用混合设计考察阅读方式和学习次数对产生效应的影响。结果发现学习次数的主效应显著,阅读方式的主效应和二者的交互作用不显著。结果表明产生效应未随着项目编码强度的增强而增强,支持特异观。     

Using morphs of familiar objects to examine how shape discriminability influences view sensitivity

We investigated how the difficulty of detecting a shape change influenced the achievement of object constancy across depth rotations for object identification and categorization tasks. In three sequential matching experiments, people saw pictures of morphs between two everyday, nameable objects (e.g., bath-sink morphs, along a continuum between "bath" and "sink" end-point shapes). In each experiment, both view changes and shape changes influenced performance. Furthermore, the deleterious effects of view changes were strongest when shape discrimination was hardest. In our earlier research, using morphs of novel objects, we found a similar interaction between view sensitivity and shape sensitivity (Lawson, 2004b; Lawson & Bülthoff, 2006; Lawson, Bülthoff, & Dumbell, 2003). The present results extend these findings to familiar-object morphs. They suggest that recognition remains view-sensitive at the basic level of identification for everyday, nameable objects, and that the difficulty of shape discrimination plays a critical role in determining the degree of this view sensitivity.     

Rewarding context accelerates implicit guidance in visual search

It is well known that observers can implicitly learn the spatial context of complex visual searches, such that future searches through repeated contexts are completed faster than those through novel contexts, even though observers remain at chance at discriminating repeated from new contexts. This contextual-cueing effect arises quickly (within less than five exposures) and asymptotes within 30 exposures to repeated contexts. In spite of being a robust effect (its magnitude is over 100 ms at the asymptotic level), the effect is implicit: Participants are usually at chance at discriminating old from new contexts at the end of an experiment, in spite of having seen each repeated context more than 30 times throughout a 50-min experiment. Here, we demonstrate that the speed at which the contextual-cueing effect arises can be modulated by external rewards associated with the search contexts (not with the performance itself). Following each visual search trial (and irrespective of a participant’s search speed on the trial), we provided a reward, a penalty, or no feedback to the participant. Crucially, the type of feedback obtained was associated with the specific contexts, such that some repeated contexts were always associated with reward, and others were always associated with penalties. Implicit learning occurred fastest for contexts associated with positive feedback, though penalizing contexts also showed a learning benefit. Consistent feedback also produced faster learning than did variable feedback, though unexpected penalties produced the largest immediate effects on search performance.     

Global shape cannot be attended without object identification.

Whether the global shape of objects can be processed without accessing semantic or identity information was tested. Ss judged which of 2 fragmented forms had the same global shape as a reference stimulus. Matching stimuli could be physically identical, semantically related, or unrelated. The reference stimulus and nonmatching (distractor) form could be semantically related or unrelated. Similarity effects in the related condition were unconfounded with matches nameable and nonnameable forms. For nameable forms, related matching forms facilitated performance; a related distractor disrupted performance. Semantic interference was eliminated when nameable distractors were replaced with nonnameable partners; semantic similarity effects on matching were eliminated with a nonnameable reference stimulus and with inverted targets and distractors. Access to information concerning global shape does not normally occur without object identification.     

Threat captures attention but does not affect learning of contextual regularities

Some of the stimulus features that guide visual attention are abstract properties of objects such as potential threat to one's survival, whereas others are complex configurations such as visual contexts that are learned through past experiences. The present study investigated the two functions that guide visual attention, threat detection and learning of contextual regularities, in visual search. Search arrays contained images of threat and non-threat objects, and their locations were fixed on some trials but random on other trials. Although they were irrelevant to the visual search task, threat objects facilitated attention capture and impaired attention disengagement. Search time improved for fixed configurations more than for random configurations, reflecting learning of visual contexts. Nevertheless, threat detection had little influence on learning of the contextual regularities. The results suggest that factors guiding visual attention are different from factors that influence learning to guide visual attention.     

Cross-situational Learning From Ambiguous Egocentric Input Is a Continuous Process: Evidence Using the Human Simulation Paradigm

Recent laboratory experiments have shown that both infant and adult learners can acquire word-referent mappings using cross-situational statistics. The vast majority of the work on this topic has used unfamiliar objects presented on neutral backgrounds as the visual contexts for word learning. However, these laboratory contexts are much different than the real-world contexts in which learning occurs. Thus, the feasibility of generalizing cross-situational learning beyond the laboratory is in question. Adapting the Human Simulation Paradigm, we conducted a series of experiments examining cross-situational learning from children's egocentric videos captured during naturalistic play. Focusing on individually ambiguous naming moments that naturally occur during toy play, we asked how statistical learning unfolds in real time through accumulating cross-situational statistics in naturalistic contexts. We found that even when learning situations were individually ambiguous, learners’ performance gradually improved over time. This improvement was driven in part by learners’ use of partial knowledge acquired from previous learning situations, even when they had not yet discovered correct word-object mappings. These results suggest that word learning is a continuous process by means of real-time information integration.     

Developmental Changes in Discrepancies Between Adolescents’ and Their Mothers’ Views of Family Communication

Prior work indicates that adolescents perceive the family more negatively than do their parents. These discrepant views comprise some of the most robust observations in psychological science, and are observed on survey reports collected in vastly different cultures worldwide. Yet, whether developmental changes occur with these discrepant views remains unclear. In a sample of 141 adolescents and their mothers, we examined 1-year developmental changes in discrepancies between parents’ and adolescents’ views of family functioning. We focused on discrepant views about a relatively covert domain of family functioning (i.e., internal views of open communication) and a relatively overt domain of such functioning (i.e., views about observable communication problems). We observed significant developmental changes in discrepant views for open communication, but not for communication problems. These findings have important implications for research examining links between discrepant views of family functioning and whether these discrepancies serve as risk or protective factors for adolescent psychosocial functioning.     

Prejudiced learning: A connectionist account

Connectionist simulation was employed to investigate processes that may underlie the relationships between prior expectancies or prejudices and the acquisition of attitudes, under conditions where learners can only discover the valence of attitude objects through directly experiencing them. We compared contexts analogous to learners holding either false negative expectancies (‘prejudices’) about a subclass of objects that were actually good or false positive expectancies about objects that were actually bad. We introduced expectancy‐related bias either by altering the probability of approach, or by varying the rate of learning following experience with good or bad objects. Where feedback was contingent on approach, the false positive expectancies were corrected by experience, but negative prejudices resisted change, since the network avoided objects deemed to be bad, and so received less corrective feedback. These findings are discussed in relation to the effects of intergroup contact and expectancy‐confirmation processes in reducing or sustaining prejudice.     

Fifteen-month-old infants attend to shape over other perceptual properties in an induction task

This study examined whether infants privilege shape over other perceptual properties when making inferences about the shared properties of novel objects. Forty-six 15-month-olds were presented with novel target objects that possessed a nonobvious property, followed by test objects that varied in shape, color, or texture relative to the target. Infants generalized the nonobvious property to test objects that were highly similar in shape, but not to objects that shared the same color or texture. These results demonstrate that infants’ attention to shape is not specific to lexical contexts and is present at the early stages of productive language development. The implications of these findings for debates about children's shape bias, in particular, and the nature of infants’ categories more generally, are discussed.     

Sensitivity to sampling in Bayesian word learning

We report a new study testing our proposal that word learning may be best explained as an approximate form of Bayesian inference (Xu & Tenenbaum, in press). Children are capable of learning word meanings across a wide range of communicative contexts. In different contexts, learners may encounter different sampling processes generating the examples of word-object pairings they observe. An ideal Bayesian word learner could take into account these differences in the sampling process and adjust his/her inferences about word meaning accordingly. We tested how children and adults learned words for novel object kinds in two sampling contexts, in which the objects to be labeled were sampled either by a knowledgeable teacher or by the learners themselves. Both adults and children generalized more conservatively in the former context; that is, they restricted the label to just those objects most similar to the labeled examples when the exemplars were chosen by a knowledgeable teacher, but not when chosen by the learners themselves. We discuss how this result follows naturally from a Bayesian analysis, but not from other statistical approaches such as associative word-learning models.     

Memory for object locations: Priority effect and sex differences in associative spatial learning

This paper reports two experiments conducted to examine priority effects and sex differences in object location memory. A new task of paired position-learning was designed, based on the A–B A–C paradigm, which was used in paired word learning. There were three different paired position-learning conditions: (1) positions of several different objects (B-objects and C-objects) around referent objects (A-objects) were learned in the A–B A–C position-learning condition, (2) positions of several different objects with no referent objects were learned in the 0–B 0–C position-learning condition, and (3) positions of identical objects (stars) with no referent objects were learned in the 0-star 0-star position-only condition. The results revealed a significant priority effect on performance in the A–B A–C and the 0–B 0–C position-learning conditions but not in the 0-star 0-star position-only condition. Contradictory results were obtained with respect to the sex variable: a female superiority effect on paired position learning was significant in Experiment 1, but this effect was not replicated in Experiment 2. In addition, an articulatory suppression task used in Experiment 2 had a significant effect on recall of different object positions but no effect on recall of identical object positions. This suggested that verbal encoding was not necessary for learning of positions of identical objects.     

Retrieval failure, rehearsal deficiency, and short-term memory loss in the aphasic adult

Studies show that aphasic patients typically are grossly impaired in short-term memory performance. Since aphasics generally experience difficulty in word retrieval, it is conceivable that short-term memory loss is partially the result of verbal rehearsal deficiency which, in turn, is caused by the word retrieval problem. This paper reports an experiment in which five aphasic adults were nonverbally to recall individualized lists of pictures they could easily name and lists of pictures they could not name. Final items in the two lists were recalled with equal accuracy; this was expected in that the recency effect usually reflects sensory rather than verbal storage. Initial items were recalled with greater accuracy than middle-list items in the nameable sets but not in the unnameable sets. This primacy effect suggests the aphasics rehearsed the nameable pictures, but both lists were recalled so poorly that rehearsal deficit was considered responsible for no more than a fraction of the aphasics' reduction in short-term memory.