Forgetting in spatial memories acquired in a virtual environment

This study examined forgetting in spatial memories acquired in a virtual environment. In the two experiments, participants learned the locations of eight objects. In Experiment 1, the objects were presented as photographs in either a laboratory or in an equivalent virtual environment. Irrespective of learning condition, accuracy of recall of the locations was found to deteriorate after a retention interval of approximately 1 week. In Experiment 2, following virtual learning, three groups of participants performed a series of non‐spatial tasks of low, intermediate or high difficulty. The tasks were presented in a retention interval of 2 hours. A comparison of recall accuracy before and after presentation of the interference tasks indicated that that the groups were not differentially affected by the difficulty of the retroactive interference tasks. However, the groups differed in their subjective assessment of the mental workload involved in the tasks. The results are discussed with reference to a prominent theory of forgetting. Copyright © 2007 John Wiley & Sons, Ltd.     

Recall cues interfere with retrieval from visuospatial working memory

Visuospatial working memory allows us to hold multiple visual objects over short delays. It is typically tested by presenting an array of objects, then after a delay showing a ‘probe’ indicating which memory item to recall or reproduce by adjusting a target feature. However, recent studies demonstrate that information at the time of probe can disrupt recall. Here, in three experiments we test whether traditional memory probes, which contain features that compete with the feature to be recalled, may themselves interfere with performance. We asked participants to report the direction of one of the several coloured arrows in memory, based on its colour. First, we demonstrate that recall is better when the probe is initially just a coloured dot, rather than a coloured arrow which has to be adjusted to match orientation memory, consistent with interference from features of the probe itself. Second, this interference is present even when a mask follows the memory array, suggesting that the interference does not work by degrading immediate or iconic memory. Finally, when items are shown sequentially, the first and last items are invulnerable to probe interference. Our findings support recent theories of associative recall, in which probes reactivate features in WM, retrieving information by pattern completion.     

On the coding of spatial information

Two experiments studied recall of objects and their locations in an intentional-incidental learning paradigm. When studying spatial information, the usual incidental condition is not truly incidental, because subjects often deliberately use locations to help organize objects for recall. Therefore, a true incidental task was devised in which neither objects nor locations were expected to be recalled and for which explicit encoding of locations was irrelevant. There was only a small loss in recall of objects or their locations in a true incidental condition. It was concluded that a great deal of location information is automatically coded into long-term memory storage in the sense that active processing is not required. The data were contrasted with incidental processing of other attributes, such as color. Although adults performed better than children, there were no age-related interactions, indicating similarity of functioning at all ages studied.     

A note on the development of recall of spatial location

Recall of spatial location was studied with 5, 8, 12--13, and 17--18 year old subjects. Pictures of objects were shown one at a time in one of the four quadrants of a projection screen which was either blank (NF) or divided by a cross into four quadrants (F). The presence of the frame (F) did not affect item recall, but facilitated location recall more, the younger the subjects. Intentional learning of location was superior to incidental learning in the youngest but not in older children. The results are in agreement with Bryant's (1974) analysis of perceptual development which emphasizes the use of external spatial frames of reference in the encoding of attributes of visual objects in young children.     

Judgements of relative direction: The effect of task instructions on spatial recall

One of the most widely used tasks in the spatial memory literature is the judgement of relative direction (JRD) test. The present investigation examined the hypothesis that standard JRD task demands bias spatial recall. In two experiments, participants' recall of small-scale layouts as measured by standard JRD tests (in which the relationship between objects was employed to establish imagined orientations within the learned scene) was compared with recall as measured by novel JRD tasks. The novel tasks emphasized either the internal front/back and left/right axes of individual objects (Experiment 1) or extrinsic spatial cues (Experiment 2). Spatial recall was found to reflect the reference cues emphasized by the JRD task in Experiment 1 and by the novel task in Experiment 2. The finding that directional judgements tended to reflect a frame of reference aligned with the set of cues emphasized by task demands suggests that the nature of the task employed to test knowledge can have an effect on spatial recall.     

Relation between verbal recall and visual recognition of the same stimuli in young children

Five-year-old children (N = 112) were shown drawings of common objects three times either as a naming-and-learning task or as a preference task (incidental learning). A verbal recall test followed by a class- and item-recognition test, scaled to reflect the accuracy of item recognition, were given either 2 min or two weeks after presentation. Intentional learning with naming led to better immediate recall than incidental learning, but the recognition and delayed recall scores were equal for the two learning conditions. The probability of verbal recall of object names was in each case uncorrelated with the accuracy of visual recognition of the same objects by the same Ss. The results are closely similar to those obtained with adult Ss by Bahrick and Boucher (1968).     

Spatial organization in the free recall of pictorial stimuli

Thirty-one young adults were presented with a series of visual arrays each containing drawings of objects. Free recall of the objects on each visual array could be organized by the spatial location of the objects or by another type of organization. The other type of organization was different on each array and comprised semantic, shape, colour, size, orientation or phonetic categories. The results showed that free recall could be organized by spatial location or by semantic, shape, colour or size categories. However, only semantic and colour category organization were found to correlate significantly with recall. To account for the correlation results, two distinct general forms of organization are hypothesized.     

空间参照系建立的时间特征*

通过2个实验来探讨空间记忆参照系建立的时间特征。被试学习一个由7个物体组成的场景,场景中的物体以随机的方式序列呈现。一个能够标明物体位置且具有对称结构的场景分别在被试进行物体位置学习之前或之后呈现。研究结果发现:当被试在学习物体位置之前短暂呈现场景结构,场景结构能够决定空间参照系的建立;但被试学习物体位置之后再短暂呈现场景结构,场景结构不能决定空间参照系的建立。以上结果表明:空间参照系是在学习物体位置之前建立,并且建立之后不能被改变。     

Forgetting curves in long-term memory: evidence for a multistage model of retention.

An experimental study with 20 normal healthy young adult subjects was performed to evaluate the interaction of type of memory tasks, type of learning modalities, and length of acquisition/recall interval. Four different tasks were employed (serial learning, paired learning, rote learning, and visuolinguistic transfer), some requiring a single trial learning modality others a multitrial learning modality. Acquisition/recall intervals were immediate, intermediate (3 min), and delayed. The experimental design allowed for the comparison of effects from five different delayed recall intervals (2, 8, 12, 24, and 48 hr). Results demonstrated a specific interaction on learning rates due to different ceiling effects for the different types of memory tasks. Forgetting rates, on the other hand, demonstrated a specific effect due to type of memory tasks and learning modalities only for differences between immediate and intermediate recall. These differences remained stable during the longer intervals and were not affected by length of interval. A multistage composition of long-term retention was suggested to explain these results, and a practical indication to build experimental procedures to study memory in the clinical field was evidenced.     

The role of visuo-spatial abilities in environment learning from maps and navigation over the adult lifespan

Visuo-spatial abilities have an important role in environment learning. The aim of the present study was to explore whether these abilities relate to spatial recall after learning an environment from a map or a video, and irrespective of the learner's age (from youth to old age). The study involved 431 participants from 25 to 84 years old, who were assessed for their visuo-spatial working memory, object-based mental rotation, and perspective-taking abilities. Then, they learned environments from a map and a video, and performed pointing, map drawing, and route repetition tasks after learning from each type of input. The resulting path models showed that age related to visuo-spatial abilities and (in some cases) to spatial accuracy, too. After accounting for age, visuo-spatial abilities also related to spatial recall performance, whatever the type of learning input, especially in pointing tasks and, to a lesser degree, in map drawing and route repetition tasks. Overall, the relationship between individual visuo-spatial abilities and environment learning relates to the learning input and the type of task used to assess recall. This relationship was found in a large and diverse sample of participants ranging from youth to old age.     

The relationship between preschoolers’ selective attention and memory for location strategies

Late and early preschoolers’ attention and spatial strategies were examined in response to instructions to recall relevant objects [Blumberg, F. C. & Torenberg, M. (2003). The impact of spatial cues on preschoolers’ selective attention. Journal of Genetic Psychology, 164, 42–53] and irrelevant objects [Blumberg, F. C. & Torenberg, M. (in press). The effects of spatial configuration on preschoolers’ selective attention and incidental learning. Infant & Child Development], and to spatial placement of objects within a multi-colored box. Sets of toy chairs or animals were designated as relevant or irrelevant and placed in each of the box's corners (corners condition), in the middle of its walls (walls condition), or in two corners and in the middle of two walls (control condition). Selective attention and spatial strategies were assessed via the removal sequence of items. Recall was assessed via correct relocations of relevant items. Older children and corners condition children showed significantly better recall than children in other conditions. Overall, most children used selective strategies, indicating that relevance of items, rather than their spatial categorization as corners or walls influenced strategy choice.     

Local temporal distinctiveness does not benefit auditory verbal and spatial serial recall

In the present study, we examined the role of randomly arranged temporal intervals preceding and following items (pre- and postitem intervals, respectively) in auditory verbal and spatial recall tasks. The duration of the pre- and postitem intervals did not affect serial recall performance. This finding calls into question (1) the suggestion that the interval following an item permits the consolidation of information in memory, even in a relatively demanding spatial task, and (2) the prediction that temporal distinctiveness should improve performance. The latter was explored further by showing that in contrast to our empirical data, a relative temporal distinctiveness model produced significant increases in recall performance when pre- and postitem intervals increased. The results are discussed with regard to recent studies revisiting the role of temporal isolation in short-term serial memory.     

Evidence of blocking with geometric cues in a virtual watermaze

Three computer based experiments, testing human participants in a non-immersive virtual watermaze task, used a blocking design to assess whether two sets of geometric cues would compete in a manner described by associative models of learning. In stage 1, participants were required to discriminate between visually distinct platforms. In stage 2, additional spatial information was provided by the shape or the color of the walls of the pool. In a test trial, the platforms were removed and the spatial knowledge acquired regarding the position of the platform was assessed. Experimental groups were compared against control groups which did not receive stage 1 training. The unique color of the correct platform, in Experiments 1 and 3, disrupted learning about the colored walls but not the geometry of the pool. In Experiment 2, the correct platform was identifiable from its position within the three platform array. Learning the relative position of the correct platform within the array disrupted learning about its position relative to the geometry of the pool, but not to the colored walls. The results suggest that learning the position of a goal in relation to the geometry of the environment can be blocked but only by an alternative geometric cue.     

Retrieving enduring spatial representations after disorientation

Four experiments tested whether there are enduring spatial representations of objects' locations in memory. Previous studies have shown that under certain conditions the internal consistency of pointing to objects using memory is disrupted by disorientation. This disorientation effect has been attributed to an absence of or to imprecise enduring spatial representations of objects' locations. Experiment 1 replicated the standard disorientation effect. Participants learned locations of objects in an irregular layout and then pointed to objects after physically turning to face an object and after disorientation. The expected disorientation was observed. In Experiment 2, after disorientation, participants were asked to imagine they were facing the original learning direction and then physically turned to adopt the test orientation. In Experiment 3, after disorientation, participants turned to adopt the test orientation and then were informed of the original viewing direction by the experimenter. A disorientation effect was not observed in Experiment 2 or 3. In Experiment 4, after disorientation, participants turned to face the test orientation but were not told the original learning orientation. As in Experiment 1, a disorientation effect was observed. These results suggest that there are enduring spatial representations of objects' locations specified in terms of a spatial reference direction parallel to the learning view, and that the disorientation effect is caused by uncertainty in recovering the spatial reference direction relative to the testing orientation following disorientation.     

Recall of order information by deaf signers: Phonetic coding in temporal order recall

To examine the claim that phonetic coding plays a special role in temporal order recall, deaf and hearing college students were tested on their recall of temporal and spatial order information at two delay intervals. The deaf subjects were all native signers of American Sign Language. The results indicated that both the deaf and hearing subjects used phonetic coding in short-term temporal recall, and visual coding in spatial recall. There was no evidence of manual or visual coding among either the hearing or the deaf subjects in the temporal order recall task. The use of phonetic coding for temporal recall is consistent with the hypothesis that recall of temporal order information is facilitated by a phonetic code.     

Recall of spatial location by the amnesic patient H.M

The amnesic patient H.M. was tested for immediate recall of the location of objects in an array. Three array-sizes were used: 16, 7, or 4 objects. With 16 objects, H.M.'s performance was at chance level; with the smaller arrays, his performance was above chance, but still well below the levels achieved by age-matched control subjects. The ability to recall location by H.M. did not differ under incidental and intentional learning conditions, thus failing to support the notion that automatic encoding skills may be selectively disrupted in amnesia.     

Reference directions and reference objects in spatial memory of a briefly viewed layout

Two experiments investigated participants' spatial memory of a briefly viewed layout. Participants saw an array of five objects on a table and, after a short delay, indicated whether the target object indicated by the experimenter had been moved. Experiment 1 showed that change detection was more accurate when non-target objects were stationary than when non-target objects were moved. This context effect was observed when participants were tested both at the original learning perspective and at a novel perspective. In Experiment 2, the arrays of five objects were presented on a rectangular table and two of the non-target objects were aligned with the longer axis of the table. Change detection was more accurate when the target object was presented with the two objects that were aligned with the longer axis of the table during learning than when the target object was presented with the two objects that were not aligned with the longer axis of the table during learning. These results indicated that the spatial memory of a briefly viewed layout has interobject spatial relations represented and utilizes an allocentric reference direction.