What Was Where? Memory for Object Locations

Three experiments are reported on short-term memory for object location. Stimulus displays containing different numbers and types of objects were presented for 30 seconds, after which subjects were required to relocate the various objects within the display, merely to reconstruct positions, or to assign objects correctly to an equal number of premarked positions. In all experiments half the trials were performed with concurrent articulatory suppression. The results support the hypothesis that two processes can be distinguished: one that underlies the construction of a positional map and one that assigns objects to positions. These processes are differentially affected by object numbers and articulatory suppression. This hypothesis is discussed in terms of Baddeley's (1986) working memory model and Kosslyn's (1987) distinction between 'categorical' and 'coordinate' spatial relations.     

Gender differences in object location memory in a real three-dimensional environment

In this preliminary study we investigate gender differences in object location memory. Our purpose is to extend the results about object location memory obtained in laboratory settings to a real 3-D environment and to further distinguish the specific components involved in this kind of memory by considering the strategies adopted to perform the task. To do this, we join the three-level model of spatial representations (landmark, route, and survey) proposed by Siegel and White (1975) with the three subcomponents of spatial memory (what, where, and what + where) identified by Postma and De Haan (1996). We adopted the object relocation task devised by Postma and De Haan (1996), adapted to a real environment. Seven common objects were placed on the floor of a cylindrical room. Sixty-four males and 64 females were asked to memorize the spatial layout. Next, the experimenter moved the objects to a different position along with seven new objects and the participants had to relocate the original objects to their initial positions. In line with Postma, Izendoorn, and De Haan (1998), we found no gender difference in object recognition, and in recalling absolute distance and categorical spatial relations; however males were better than females in recalling the distance between objects and the size of the layout. Overall, the data show a male advantage in some components of spatial cognition closely linked to the encoding of the metric structure of the spatial relationships at both route and survey level.     

Gender differences in memory for objects and their locations: a study on automatic versus controlled encoding and retrieval contexts

Object-location memory is the only spatial task where female subjects have been shown to outperform males. This result is not consistent across all studies, and may be due to the combination of the multi-component structure of object location memory with the conditions under which different studies were done. Possible gender differences in object location memory and its component object identity memory were assessed in the present study. In order to disentangle these two components, an object location memory task (in which objects had to be relocated in daily environments), and a separate object identity recognition task were carried out. This study also focused on the conditions under which object locations were encoded and retrieved. Only half of the participants were aware of the fact that object locations had to be retrieved later on. Moreover, by applying the 'process dissociation procedure' to the object location memory assessments and the 'remember-know' paradigm to the object identity measure, the amount of explicit (conscious) and implicit (unconscious) retrieval was estimated for each component. In general, females performed better than males on the object location memory task. However, when controlled for object identity memory, females no longer outperformed males, whereas they did not obtain a higher general object identity memory score, nor did they have more explicit or implicit recollection of the object identities. These complicated effects might stem from a difference between males and females, in the way locations or associations between objects and locations are retrieved. In general, participants had more explicit (conscious) recollection than implicit (unconscious) recollection. No effect of encoding context was found, nor any interaction effect of gender, encoding and retrieval context.     

Selective storage and maintenance of an object’s features in visual working memory

It has been shown that we have a highly capacity-limited representational space with which to store objects in visual working memory. However, most objects are composed of multiple feature attributes, and it is unknown whether observers can voluntarily store a single attribute of an object without necessarily storing all of its remaining features. In this study, we used a masking paradigm to measure the efficiency of encoding, and neurophysiological recordings to directly measure visual working memory maintenance while subjects viewed multifeature objects and were required to remember only a single feature or all of the features of the objects. We found that measures of both encoding and maintenance varied systematically as a function of which object features were task relevant. These experiments show that individuals can control which features of an object are selectively stored in working memory.     

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.     

Incidental and intentional visual memory: What memories are and are not affected by encoding tasks?

Prior research into the impact of encoding tasks on visual memory (Castelhano & Henderson, 2005) indicated that incidental and intentional encoding tasks led to similar memory performance. The current study investigated whether different encoding tasks impacted visual memories equally for all types of objects in a conjunction search (e.g., targets, colour distractors, object category distractors, or distractors unrelated to the target). In sequences of pictures, participants searched for prespecified targets (e.g., green apple; Experiment 1), memorized all objects (Experiment 2), searched for specified targets while memorizing all objects (Experiment 3), searched for postidentified targets (Experiment 4), or memorized all objects with one object prespecified (Experiment 5). Encoding task significantly improved visual memory for targets and led to worse memory for unrelated distractors, but did not influence visual memory of distractors that were related to the target's colour or object category. The differential influence of encoding task indicates that the relative importance of the object both positively and negatively influences the memory retained.     

Spatial distinctiveness effect in categorisation

The aim of the present study was to show that the probability of an item being retrieved is proportional to its spatial distinctiveness, and that this distinctiveness effect can be obtained in an implicit memory task. The participants were presented with two phases in which they had to categorise pictures of objects as either “kitchen utensils” or “do-it-yourself tools”. In our encoding phase, the pictures were successively presented in different positions on the screen. The positions were arranged in one of two different configurations: a “distinctive condition” in which the pictures were placed in two circles, one central and one peripheral, such that the distance between the pictures was greater when they were in a peripheral position than in a central position, and a “nondistinctive” condition, in which the distance between the pictures was constant irrespective of their central or peripheral position. In the test phase, the same pictures were presented for categorisation, mixed with new pictures at the centre of the screen. The results clearly confirmed our expectations.     

Reconciling change blindness with long-term memory for objects

How can we reconcile remarkably precise long-term memory for thousands of images with failures to detect changes to similar images? We explored whether people can use detailed, long-term memory to improve change detection performance. Subjects studied a set of images of objects and then performed recognition and change detection tasks with those images. Recognition memory performance exceeded change detection performance, even when a single familiar object in the postchange display consistently indicated the change location. In fact, participants were no better when a familiar object predicted the change location than when the displays consisted of unfamiliar objects. When given an explicit strategy to search for a familiar object as a way to improve performance on the change detection task, they performed no better than in a 6-alternative recognition memory task. Subjects only benefited from the presence of familiar objects in the change detection task when they had more time to view the prechange array before it switched. Once the cost to using the change detection information decreased, subjects made use of it in conjunction with memory to boost performance on the familiar-item change detection task. This suggests that even useful information will go unused if it is sufficiently difficult to extract.     

Memory for object location: a span study in children.

The aim of the present study was to analyze the developmental changes in three spatial processes, namely, in positional reconstruction involving the retention of spatial locations per se (Positional encoding task), in the assignment of objects to positions (Object-to-position assignment task), and in the integration of these two (Combined task). A span procedure was used to assess the development of spatial memory in children aged 6, 8, and 10 years tested in these three tasks. The findings of the present study provide developmental spans for each relocation task. Results show an age-dependent improvement in all tasks, suggesting that spatial position is not automatically encoded. The results also show different developmental patterns for the relocation tasks considered, suggesting that spatial memory comprises a number of different component processes.     

客体工作记忆任务中大脑皮层活动的记忆负荷效应

利用128导事件相关电位技术,采用延迟匹配任务的实验范式,测查了20名正常被试完成不同负荷客体任务时的皮层慢电位（slow cortical potentials,简称sp成分）,实验发现：背侧前额叶在刺激呈现后的700ms到1400ms出现记忆负荷效应,高负荷任务诱发的sp成分显著负于低负荷任务;低负荷任务诱发的sp成分在左前额区（500~1800ms）、左前额-中央区（700~1800ms）、左中央-顶叶区（1000~1400s和1800~4800ms）、右前额区（1800~4800ms）和右前额-中央区（1400~4800ms）显著负于高负荷任务,出现记忆负荷效应,但这种负荷效应在左右大脑半球所反映的心理意义可能不同     

Chimpanzees (Pan troglodytes) recognize spatial and object correspondences between a scale model and its referent

In the present study, the contributions of spatial and object features to chimpanzees' comprehension of scale models were examined. Seven chimpanzees that previously demonstrated the ability to use a scale model as an information source for the location of a hidden item were tested under conditions manipulating the feature correspondence and spatial-relational correspondence between objects in the model and an outdoor enclosure. In Experiment 1, subjects solved the task under two conditions in which one object cue (color or shape) was unavailable, but positional cues remained. Additionally, performance was above chance under a third condition in which both types of object cues, but not position cues, were available. In Experiment 2, 2 subjects solved the task under a condition in which shape and color object cues were simultaneously unavailable. The results suggest that, much like young children, chimpanzees are sensitive to both object and spatial-relational correspondences between a model and its referent.     

A dissociation between judged causality and imagined locations in simple dynamic scenes

To mentally extrapolate the trajectory of a moving object that disappears from sight, different sources of information can be exploited: memory of its last visible position, its inferred movement through time, and general understanding of the causal structure of the scene. It is often assumed that these cues are integrated into unified analog mental representations. In our experiment, participants predicted the position of an object that disappeared behind an occluder and estimated the degree to which the movement was caused by another object. They made considerable errors in predicting imagined displacements. Moreover, their predictions were misaligned with their judgments of causality. They predicted the positions of the invisible moving objects better in events that they judged less causally correct than in events that they judged more causally correct. These results suggest that physical and cognitive parameters of imagined dynamic events do not merge into unitary mental models simulating actual states of the world.     

Effects of attention during encoding on sex differences in object location memory

Attention plays a key role in memory processes and has been widely studied in various memory tasks. The role of attention in sex differences in object location memory is not clearly understood. In the present study, two experiments involving 186 participants and using an object array presented on paper were conducted to examine two encoding conditions: incidental and intentional. In each experiment, the participants were randomly assigned to divided versus full attention conditions. In the first experiment, which involved incidental encoding, women outperformed men in memorising location‐exchanged objects in both the full and in the divided attention condition. In the second experiment, which involved intentional encoding, women outperformed men in memorising location‐exchanged objects in the full attention condition, but not the divided attention condition. These findings deepen our knowledge regarding the role of attention in object location memory, specifically in terms of the conditions under which females have an advantage for detecting changes in an array of objects.     

The time course of object encoding

Four experiments examined the effects of encoding time on object identification priming and recognition memory. After viewing objects in a priming phase, participants identified objects in a rapid stream of non-object distracters; display times were gradually increased until the objects could be identified (Experiments 1-3). Participants also made old/new recognition judgments about previously viewed objects (Experiment 4). Reliable priming for object identification occurred with 150 ms of encoding and reached a maximum after about 300 ms of encoding time. In contrast, reliable recognition judgments occurred with 75 ms of encoding and continued to improve for encoding times of up to 1200 ms. These results suggest that recognition memory may be based on multiple levels of object representation, from rapidly activated representations of low-level features to semantic knowledge associated with the object. In contrast, priming in this object identification task may be tied specifically to the activation of representations of object shape.     

Attentional demands and recall of verbal and color information in action events

Two experiments addressed the influence of secondary task performance at encoding on recall of different features of subject-performed tasks (SPTs) involving objects (e.g., turn the wallet). In Experiment 1, memory for verbs and colors of objects was assessed, with object names serving as cues. In Experiment 2, object and color memory were assessed, with verbs serving as cues. Results from both experiments indicated a greater deterioration of memory performance under divided attention for verbal features than for colors. In addition, intention to remember did not affect performance for any feature in either experiment. The overall pattern of outcome is discussed relative to the view that encoding of verbal features of SPTs is more attention-demanding than encoding of physical task features, such as color.     

Flexibility in Visual Working Memory: Accurate Change Detection in the Face of Irrelevant Variations in Position

Many recent studies of visual working memory have used change-detection tasks in which subjects view sequential displays and are asked to report whether they are identical or if one object has changed. A key question is whether the memory system used to perform this task is sufficiently flexible to detect changes in object identity independent of spatial transformations, but previous research has yielded contradictory results. To address this issue, the present study compared standard change-detection tasks with tasks in which the objects varied in size or position between successive arrays. Performance was nearly identical across the standard and transformed tasks unless the task implicitly encouraged spatial encoding. These results resolve the discrepancies in prior studies and demonstrate that the visual working memory system can detect changes in object identity across spatial transformations.     

Configural representations in spatial working memory

Two studies investigate the nature of representations in spatial working memory, directly addressing the question of whether people represent the configuration information above and beyond independent positional information when representing multiple sequentially presented locations. In Experiment 1, participants performed a location memory task in which they recalled the location of objects that were presented sequentially on a screen. Comparison of participants' data with simulated data modelled to represent independent positional representation of spatial locations revealed that participants represented the configural properties of shorter sequences (3 and 4 locations) but not of longer ones (5 and 7 locations). Experiment 2 employed a sequential recognition task in which participants were asked to judge whether two consequently presented spatial sequences were identical. These experiments confirmed sensitivity to configural properties of spatial sequences.