An isolation effect in serial memory for spatial information

This paper reports the first demonstration of an isolation effect or von Restorff effect (von Restorff, 1933) in the context of a spatial-memory task: Short-term serial recall was enhanced for both the location and the serial position of one red dot presented amongst a sequence of otherwise black dots. When the serial position of the isolate was fixed, the spatial isolation effect only emerged when participants received a control block of trials before the block of isolation trials (Experiment 1). However, when the serial position of the isolate was varied across isolation trials, an isolation effect was still produced regardless of condition order (Experiment 2). It is suggested that both temporal grouping strategies and greater item-specific processing may have contributed to the enhanced retention of the isolate.     

An isolation effect in serial memory for spatial information

This paper reports the first demonstration of an isolation effect or von Restorff effect (von Restorff, 1933 von Restorff, H. 1933. Uber die Wirkung von Bereichsbildungen im Spurenfeld [On the effect of spheres formations in the trace field]. Psychologische Forschung, 18: 299–342. [Crossref] , [Google Scholar]) in the context of a spatial-memory task: Short-term serial recall was enhanced for both the location and the serial position of one red dot presented amongst a sequence of otherwise black dots. When the serial position of the isolate was fixed, the spatial isolation effect only emerged when participants received a control block of trials before the block of isolation trials (Experiment 1). However, when the serial position of the isolate was varied across isolation trials, an isolation effect was still produced regardless of condition order (Experiment 2). It is suggested that both temporal grouping strategies and greater item-specific processing may have contributed to the enhanced retention of the isolate.     

The effect of path length and display size on memory for spatial information

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.     

The effect of memory load on cortical activity in the spatial working memory circuit

Accumulating evidence from electrophysiology and neuroimaging studies suggests that spatial working memory is subserved by a network of frontal and parietal regions. In the present study, we parametrically varied the memory set size (one to four spatial locations) of a delayed-response task and applied time-resolved fMRI to study the influence of memory load upon the spatial working memory circuit. Our behavioral results showed that performance deteriorates (lower accuracy and longer reaction time) as memory load increases. Memory load influenced cortical activity during the cue, delay, and response phases of the delayed-response task. Although delay-related activity in many regions increased with increasing memory load, it also was significantly reduced in the middle frontal gyrus and frontal eye fields and leveled off in the parietal areas when memory load increased further. Delayrelated activity in the left posterior parietal cortex was also lower during the error trials, in comparison with the correct trials. Our findings indicate that the delay period activity in the spatial working memory circuit is load sensitive and that the attenuation of this signal is the neural manifestation of performance limitation in the face of excessive memory load.     

A spatial modality effect in serial memory

In 2 experiments, the authors tested whether the classical modality effect-that is, the stronger recency effect for auditory items relative to visual items-can be extended to the spatial domain. An order reconstruction task was undertaken with four types of material: visual-spatial, auditory-spatial, visual-verbal, and auditory-verbal. Similar serial position curves were obtained regardless of the nature of the to-be-remembered sequences, with the exception that a modality effect was found with spatial as well as with verbal materials. The results are discussed with regard to a number of models of short-term memory.     

The effect of spatial and nonspatial contextual information on visual object memory

Recent research has found visual object memory can be stored as part of a larger scene representation rather than independently of scene context. The present study examined how spatial and nonspatial contextual information modulate visual object memory. Two experiments tested participants’ visual memory by using a change detection task in which a target object's orientation was either the same as it appeared during initial viewing or changed. In addition, we examined the effect of spatial and nonspatial contextual manipulations on change detection performance. The results revealed that visual object representations can be maintained reliably after viewing arrays of objects. Moreover, change detection performance was significantly higher when either spatial or nonspatial contextual information remained the same in the test image. We concluded that while processing complex visual stimuli such as object arrays, visual object memory can be stored as part of a comprehensive scene representation, and both spatial and nonspatial contextual changes modulate visual memory retrieval and comparison.     

The processing of spatial information in short-term memory: Insights from eye tracking the path length effect

Effects of averageness and symmetry on the judgment of facial attractiveness were investigated using a generalized Procrustes method and multiple regression analyses. Participants (n = 114) rated attractiveness of 96 photographs of faces with neutral expressions. Through a generalized Procrustes method, the faces and their mirror-reversed versions were represented as points on a hyperplane. Both averageness and symmetry of each individual were defined as distances on the plane. A multiple regression analysis was performed to examine the effect of symmetry and averageness for each gender. For male faces, both symmetry and averageness affected attractiveness ratings positively , and there was no difference between the effects of averageness and symmetry. On the other hand, for female faces only averageness affected attractiveness, whereas symmetry did not. However, these effects were not large.     

The interplay of spatial attention and memory: evidence for memory-driven spatial compatibility effects, but not for a facilitating role of attention in memory retrieval

The visual indexing theory proposed by Zenon Pylyshyn (Cognition, 32, 65-97, 1989) predicts that visual attention mechanisms are employed when mental images are projected onto a visual scene. Recent eye-tracking studies have supported this hypothesis by showing that people tend to look at empty places where requested information has been previously presented. However, it has remained unclear to what extent this behavior is related to memory performance. The aim of the present study was to explore whether the manipulation of spatial attention can facilitate memory retrieval. In two experiments, participants were asked first to memorize a set of four objects and then to determine whether a probe word referred to any of the objects. The results of both experiments indicate that memory accuracy is not affected by the current focus of attention and that all the effects of directing attention to specific locations on response times can be explained in terms of stimulus-stimulus and stimulus-response spatial compatibility.     

The target effect: Visual memory for unnamed search targets

Search targets are typically remembered much better than other objects even when they are viewed for less time. However, targets have two advantages that other objects in search displays do not have: They are identified categorically before the search, and finding them represents the goal of the search task. The current research investigated the contributions of both of these types of information to the long-term visual memory representations of search targets. Participants completed either a predefined search or a unique-object search in which targets were not defined with specific categorical labels before searching. Subsequent memory results indicated that search target memory was better than distractor memory even following ambiguously defined searches and when the distractors were viewed significantly longer. Superior target memory appears to result from a qualitatively different representation from those of distractor objects, indicating that decision processes influence visual memory.     

The revelation effect for autobiographical memory: A mixture-model analysis

Participants provided information about their childhood by rating their confidence about whether they had experienced various events (e.g., “broke a window playing ball”). On some trials, participants unscrambled a key word from the event phrase (e.g., wdinwo—window) or an unrelated word (e.g., gnutge—nugget) before seeing the event and giving their confidence ratings. The act of unscrambling led participants to increase their confidence that the event occurred in their childhood, but only when the confidence rating immediately followed the act of unscrambling. This increase in confidence mirrors the “revelation effect” observed in word recognition experiments. In the present article, we analyzed our data using a new signal detection mixture distribution model that does not require the researcher to know the veracity of memory judgments a priori. Our analysis reveals that unscrambling a key word or an unrelated word affects response bias and discriminability in autobiographical memory tests in ways that are very similar to those that have been previously found for word recognition tasks.     

The effect of pointing on spatial working memory in a 3D virtual environment

Pointing to locations can either help or hinder people's ability to recall spatial information. Prior research has focused on two‐dimensional spatial memory and pointing in real world tasks. The effect of pointing on three‐dimensional spatial memory in virtual environments remains unexplored. We examine this effect by comparing participants' recall when they point to and memorize a series of three‐dimensional locations using a gesture interface, and when they only passively view and memorize the spatial array. Thirty‐three participants completed 50 trials in both conditions. The results reveal that pointing has a negative effect on memory in the three‐dimensional virtual environment. These findings held across memory in the x–y plane of the computer screen as well as memory in the virtual third dimension. When they pointed during encoding, participants also responded more slowly, suggesting a higher cognitive load. Thus, active pointing may cause interference when users are simultaneously performing spatial memorization tasks.     

The effect of hypothermia on the rat's spatial memory in the water tank task

The effect of hypothermia on the retention of the water tank navigation task has been examined in 21 male hooded rats. After a 3-min swimming test on Day 1 the animals were trained on Days 2 and 3 (2 X 12 trials) to find a small submerged platform 1 cm below the surface of a large pool (120 cm in diameter) of opaque water. On Day 4, the rats were divided into three groups (n = 7) which were cooled to colonic temperatures of 22-24 degrees C (H1), 25-27 degrees C (H2), and 28-31 degrees C (H3), respectively, and given 12 retrieval trials in the water tank. Average escape latencies increased from 6 s in normothermic rats on Day 3 to 33, 19, and 12 s on Day 4 in the H1, H2, and H3 groups, respectively. Under the same testing conditions the performance of groups H1, H2, and H3 improved on Day 5 to 20, 8 and 6 s, respectively. It is concluded that spatial memory retrieval is resistant to mild hypothermia (30 degrees C), but that it is severely impaired at body temperatures below 25 degrees C. Reacquisition of the task is slowed down but not fully prevented in deep hypothermia.     

The time course of spatial memory distortions

Four experiments investigated the memory distortions for the location of a dot in relation to two horizontally aligned landmarks. In Experiment 1, participants reproduced from memory a dot location with respect to the two landmarks. Their performance showed a systematic pattern of distortion that was consistent across individual participants. The three subsequent experiments investigated the time course of spatial memory distortions. Using a visual discrimination task, we were able to map the emergence of spatial distortions within the first 800 msec of the retention interval. After retention intervals as brief as 50 msec, a distortion was already present. In all but one experiment, the distortion increased with longer retention intervals. This early onset of spatial memory distortions might reflect the almost immediate decay of detailed spatial information and the early influence of an enduring spatial memory representation, which encodes spatial information in terms of the perceived structure of space.     

The representation of spatial information in memory

Following memorisation of the spatial arrangement of an array of circles, subjects were asked to recall the circles in a type of free-recall task designed to determine the structure of the memorised information. Their performance showed that the circles tended to be recalled in an order that corresponded with a top-to-bottom ordering of circles on the array. In a second experiment the input order of the circles was varied by presenting them successively. The results indicated that input order influenced recall order. The implications for hypotheses about the structure and manipulation of stored spatial information were discussed.     

Head for the hills: The influence of environmental slant on spatial memory organization

Environmental slant is known to improve navigation performance in humans and other animals. Successful navigation relies on accurate spatial orientation and accurate spatial memory retrieval. The role of environmental slant in spatial orientation has been established, but its role in spatial memory organization is unclear. Two experiments using immersive virtual reality explored the influence of environmental slant on reference frame selection during spatial learning. Participants studied object locations on a sloped surface. When no additional environmental cues were present (Experiment 1), spatial memory retrieval was best from the studied perspective aligned with the direction of slope. When the direction of slope was placed in competition with the axis of the surrounding room (Experiment 2), spatial memory retrieval was best from the initially studied perspective. The latter finding contrasts with the results of research showing that pigeons preferentially rely on environmental slant over room shape. The findings are discussed in the context of spatial memory theory.     

Developmental aspects of memory for spatial location

The purpose was to show whether or not the encoding of location met criteria defining an automatic process (L. Hasher & R. T. Zacks, 1979, Journal of Experimental Psychology: General, 108, 356-388; 1984, American Psychologist, 39, 1372-1388). Among other criteria, automatic processes are not expected to show developmental changes beyond an early age, to be unrelated to intelligence level, and to be unaffected by instructions. In the first experiment preschool through sixth-grade children were compared on a 40-picturebook task following incidental (remember the names of pictures) or intentional (remember location) instruction. Subjects viewed and named pictures in sets of four, arranged in quadrants in the opened book, and then attempted to recall names of the objects pictured and to relocate pictures on blank pages. In the second experiment, second and sixth graders, college students, elderly persons, and mentally retarded persons were compared on a 60-picturebook task following either incidental or semantic incidental instructions (give the function of objects pictured). Memory for location was invariant across age groups and intelligence level. The only exception was that 3 and 4 year olds were more accurate following intentional instructions. Otherwise there were no differences between intentional and incidental instructions. Semantic instructions resulted in slightly more accurate locations. The results were interpreted as supportive of the Hasher and Zacks' automaticity hypothesis.     

Distinctiveness in serial memory for spatial information

Several studies have shown that recall performance depends on the extent to which an item differs from other items in a sequence (the distinctiveness effect; see, e.g., Kelley & Nairne, 2001). Distinctiveness effects, however, have been demonstrated mainly in the verbal domain. The present study extends distinctiveness effects to the spatial domain. In two experiments, participants recalled the order in which series of spatially located dots had been presented. Item discriminability was varied within the sequence by manipulating the duration of the interval inserted between the presentation of the dots (Experiment 1) and the perceptual characteristics of the stimuli (Experiment 2). The results showed that these manipulations in the spatial domain produce distinctiveness effects similar to those observed with verbal material (see, e.g., Neath & Crowder, 1990) and suggest that distinctiveness models of memory should take into account the processing of spatial information.     

Short-term memory for spatial and temporal information

Two experiments examined the probed recall of visually presented letter sequences in which the items appeared at different spatial locations. Three types of probe were compared: (1) spatial position; (2) temporal association; and (3) combined position and association. In the first experiment, in which the spatial locations of the items were correlated with their temporal order, spatial probes were more effective than temporal association probes. In the second experiment spatial location was uncorrelated with temporal order, and spatial probes were less effective than temporal association probes. Regardless of the probe, errors tended to be items presented close in time to correct responses: spatial proximity was far less important. The results are discussed in terms of a storage system in which items and their spatial locations are organized within a temporal format. Both experiments showed superior combined probe performance, demonstrating that short-term retrieval is not limited to the use of one type of cue at a time. Secondary aspects of the results showed additionally that subjects can “edit” their responses to avoid making obvious mistakes, and that spatial location can be partially forgotten rather than being completely lost.     

Spatial language influences memory for spatial scenes

Does language influence recognition for spatial scenes? In Experiments 1 and 2, participants viewed ambiguous pictures, with or without spatial sentences. In a yes—no recognition task, only the spatial sentences group made more false alarms toward the center of the spatial category than in the other direction; three other comparison groups showed no such tendency. This shift toward the core of the semantic category suggests that spatial language interacted with perceptual information during encoding. In Experiment 3, we varied the materials to test the interactive encoding account against a separate encoding account in which separately stored sentences are accessed during picture recognition. The results support the interactive encoding account in which spatial language influences the encoding and memory of spatial relations.