Is the map in our head oriented north?

We examined how a highly familiar environmental space--one's city of residence--is represented in memory. Twenty-six participants faced a photo-realistic virtual model of their hometown and completed a task in which they pointed to familiar target locations from various orientations. Each participant's performance was most accurate when he or she was facing north, and errors increased as participants' deviation from a north-facing orientation increased. Pointing errors and latencies were not related to the distance between participants' initial locations and the target locations. Our results are inconsistent with accounts of orientation-free memory and with theories assuming that the storage of spatial knowledge depends on local reference frames. Although participants recognized familiar local views in their initial locations, their strategy for pointing relied on a single, north-oriented reference frame that was likely acquired from maps rather than experience from daily exploration. Even though participants had spent significantly more time navigating the city than looking at maps, their pointing behavior seemed to rely on a north-oriented mental map.     

Intrinsic frames of reference in haptic spatial learning

It has been proposed that spatial reference frames with which object locations are specified in memory are intrinsic to a to-be-remembered spatial layout (intrinsic reference theory). Although this theory has been supported by accumulating evidence, it has only been collected from paradigms in which the entire spatial layout was simultaneously visible to observers. The present study was designed to examine the generality of the theory by investigating whether the geometric structure of a spatial layout (bilateral symmetry) influences selection of spatial reference frames when object locations are sequentially learned through haptic exploration. In two experiments, participants learned the spatial layout solely by touch and performed judgments of relative direction among objects using their spatial memories. Results indicated that the geometric structure can provide a spatial cue for establishing reference frames as long as it is accentuated by explicit instructions (Experiment 1) or alignment with an egocentric orientation (Experiment 2). These results are entirely consistent with those from previous studies in which spatial information was encoded through simultaneous viewing of all object locations, suggesting that the intrinsic reference theory is not specific to a type of spatial memory acquired by the particular learning method but instead generalizes to spatial memories learned through a variety of encoding conditions. In particular, the present findings suggest that spatial memories that follow the intrinsic reference theory function equivalently regardless of the modality in which spatial information is encoded.     

Selecting spatial frames of reference for visual target localization

This study examined the selection of spatial frames of reference for target localization in visual search. Participants searched for local target characters in global character configurations. The local targets could be localized relative to the character configuration in which they were embedded or relative to the presentation screen on which the configurations were displayed. We investigated under which conditions the configurations, or the screen served as frame of reference for target localization. Three experiments revealed an increasing impact of screen-related target localization with decreasing spatial uncertainty of targets in screen-related coordinates. The results indicate the capability of the visual system to localize relevant visual stimuli with respect to those frames of reference that yield the most redundant spatial distribution of these stimuli.     

Inhibition within a reference frame during the interpretation of spatial language

Spatial terms such as right are potentially ambiguous because they can refer to different regions of space when defined by competing reference frames (e.g., my right within a relative reference frame versus an object's right within an intrinsic reference frame). In such situations, previous research has suggested that multiple reference frames are initially activated, followed by inhibition of the reference frame that is not ultimately selected to define the spatial term. Reference frames are complex multi-component representations, raising the question of exactly which components of the non-selected frame are inhibited. It is possible that the whole frame may be inhibited, including all axes and endpoints, or that only select endpoints and axes may be inhibited. Three experiments conducted using a negative priming paradigm revealed that only certain components of the non-selected reference frame were inhibited, consistent with the idea that some axes are privileged. These results also suggest that the components of a reference frame can be independently accessed. Implications for representing and accessing spatial information are discussed.     

Geometric cues,reference frames,and the equivalence of experienced-aligned and novel-aligned views in human spatial memory

Spatial memories are often organized around reference frames, and environmental shape provides a salient cue to reference frame selection. To date, however, the environmental cues responsible for influencing reference frame selection remain relatively unknown. To connect research on reference frame selection with that on orientation via environmental shape, we explored the extent to which geometric cues were incidentally encoded and represented in memory by evaluating their influence on reference frame selection. Using a virtual environment equipped with a head-mounted-display, we presented participants with to-be-remembered object arrays. We manipulated whether the experienced viewpoint was aligned or misaligned with global (i.e., the principal axis of space) or local (i.e., wall orientations) geometric cues. During subsequent judgments of relative direction (i.e., participants imagined standing at one object, facing a second object, and pointed toward a third object), we show that performance was best when imagining perspectives aligned with these geometric cues; moreover, global geometric cues were sufficient for reference frame selection, global and local geometric cues were capable of exerting differential influence on reference frame selection, and performance from experienced-imagined perspectives was equivalent to novel-imagined perspectives aligned with geometric cues. These results explicitly connect theory regarding spatial reference frame selection and spatial orientation via environmental shape and indicate that spatial memories are organized around fundamental geometric properties of space.     

Cross-sensory transfer of reference frames in spatial memory

Two experiments investigated whether visual cues influence spatial reference frame selection for locations learned through touch. Participants experienced visual cues emphasizing specific environmental axes and later learned objects through touch. Visual cues were manipulated and haptic learning conditions were held constant. Imagined perspective taking when recalling touched objects was best from perspectives aligned with visually-defined axes, providing evidence for cross-sensory reference frame transfer. These findings advance spatial memory theory by demonstrating that multimodal spatial information can be integrated within a common spatial representation.     

Flexible use of spatial cues in the southern flying squirrel (<Emphasis Type="Italic">Glaucomys volans</Emphasis>)

Insects, birds, and mammals have been shown capable of encoding spatial information in memory using multiple strategies or frames of reference simultaneously. These strategies include orientation to a goal-specific cue or beacon, to the position of the goal in an array of local landmarks, or to its position in the array of distant landmarks, also known as the global frame of reference. From previous experiments, it appears that birds and mammals that scatter hoard rely primarily on a global frame of reference, but this generalization depends on evidence from only a few species. Here we examined spatial memory in a previously unstudied scatter hoarder, the southern flying squirrel. We dissociated the relative weighting of three potential spatial strategies (beacon, global, or relative array strategy) with three probe tests: transposition of beacon and the rotation or the expansion of the array. The squirrels’ choices were consistent with a spatial averaging strategy, where they chose the location dictated by at least two of the three strategies, rather than using a single preferred frame of reference. This adaptive and flexible heuristic has not been previously described in animal orientation studies, yet it may be a common solution to the universal problem of encoding and recalling spatial locations in an ephemeral physical landscape.     

Remembering object position in the absence of vision: egocentric, allocentric, and egocentric decentred frames of reference

In three experiments we examined whether memory for object locations in the peri-personal space in the absence of vision is affected by the correspondence between encoding and test either of the body position or of the reference point. In particular, the study focuses on the distinction between different spatial representations, by using a paradigm in which participants are asked to relocate objects explored haptically. Three frames of reference were systematically compared. In experiment 1, participants relocated the objects either from the same position of learning by taking as reference their own body (centred egocentric condition) or from a 90 degrees decentred position (allocentric condition). Performance was measured in terms of linear distance errors and angular distance errors. Results revealed that the allocentric condition was more difficult than the centred egocentric condition. In experiment 2, participants performed either the centred egocentric condition or a decentred egocentric condition, in which the body position during the test was the same as at encoding (egocentric) but the frame of reference was based on a point decentred by 90 degrees. The decentred egocentric condition was found to be more difficult than the centred egocentric condition. Finally, in experiment 3, participants performed in the decentred egocentric condition or the allocentric condition. Here, the allocentric condition was found to be more difficult than the decentred egocentric condition. Taken together, the results suggest that also in the peripersonal space and in the absence of vision different frames of reference can be distinguished. In particular, the decentred egocentric condition involves a frame of reference which seems to be neither allocentric nor totally egocentric.     

Spatial updating according to a fixed reference direction of a briefly viewed layout

Three experiments examined the role of reference directions in spatial updating. Participants briefly viewed an array of five objects. A non-egocentric reference direction was primed by placing a stick under two objects in the array at the time of learning. After a short interval, participants detected which object had been moved at a novel view that was caused by table rotation or by their own locomotion. The stick was removed at test. The results showed that detection of position change was better when an object not on the stick was moved than when an object on the stick was moved. Furthermore change detection was better in the observer locomotion condition than in the table rotation condition only when an object on the stick was moved but not when an object not on the stick was moved. These results indicated that when the reference direction was not accurately indicated in the test scene, detection of position change was impaired but this impairment was less in the observer locomotion condition. These results suggest that people not only represent objects’ locations with respect to a fixed reference direction but also represent and update their orientation according to the same reference direction, which can be used to recover the accurate reference direction and facilitate detection of position change when no accurate reference direction is presented in the test scene.     

Object localisation and frames of reference

In this paper, we explore which spatial frames of reference, egocentric or allocentric, are used to locate objects either in relation to ourselves (i.e. subject-to-object localisation) or to other objects (i.e. object-to-object localisation). In particular, we wanted to know whether the same or different frames of reference are used in these two different kinds of localisation after learning the environment in an egocentric way. Egocentric frames of reference are determined by the position of the person in relation to the spatial layout, whereas allocentric frames of reference are centred on the environment or on objects, independent of a persons position. We hypothesised that subject-to-object localisation is based on egocentric spatial representations, whereas object-to-object localisation is based on allocentric spatial representations. Participants were asked to study eight common objects, placed in a circle. Next, half of the participants had to point to an object in relation to their imagined position (egocentric condition) and the other half to an object in relation to another object (allocentric condition). The overall results show no difference between subject-to-object and object-to-object localisation. In both cases, access to positions corresponding to the front/back body axis was facilitated, in terms of both latency and error. Moreover, participants were able to retrieve objects positions better from the perspective from which they had learned the spatial array than from new perspectives. These results support the conclusion that egocentric coordinates, which are selected on the basis of our body-centred experience of the environment, define spatial representations underlying both subject-to-object and object-to-object localisation.     

空间场景表征中的参照系选取

被试在矩形房间中从两个不同的观察点学习物体场景并在多个朝向上对物体形成的空间关系进行判断,通过控制场景中物体主要内在轴相对于环境结构（房间和地毯）的方向和被试的学习顺序,探讨被试在场景空间表征中采用何种参照系和参照系选取时的影响因素。两个实验结果发现：（1）内在参照系（intrinsic reference systems）和环境参照系均可以用于物体场景的表征,两类参照系之间的关系却是影响被试物体场景表征时参照系选取的重要因素,即当内在参照系与环境参照系方向一致时,被试无论从哪个朝向学习,都选择从垂直于内在参照系和环境参照系的朝向进行表征。反之,当二者方向不一致时,表征时参照系的选择取决于被试的学习经历;（2）无论内在参照系与环境参照系方向是否一致,物体场景本身内在结构的规则性都能够促进空间记忆,即内在结构的规则性既有助于准确编码物体的相对位置,也有助于提高空间关系判断的准确性。     

Egocentric and geocentric frames of reference in memory of large-scale space

This experiment investigated the frames of reference used in memory to represent the spatial structure of a large-scale outdoor environment. Participants learned the locations of eight objects in an unfamiliar city park by walking through the park on one of two prescribed paths that encircled a large rectangular building. The aligned path was oriented with the building; the misaligned path was rotated by 45°. Later, participants pointed to target objects from imagined vantage points using their memories. Pointing accuracy was higher in the aligned than in the misaligned path group, and the patterns of results differed: In the aligned condition, accuracy was higher for imagined headings parallel to legs of the path and for an imagined heading oriented toward a nearby lake, a salient landmark. In the misaligned condition, pointing accuracy was highest for the imagined heading oriented toward the lake, and decreased monotonically with angular distance. These results indicated that locations of objects were mentally represented in terms of frames of reference defined by the environment but selected on the basis of egocentric experience.     

Sustained attention to local and global target features is different: Performance and tympanic membrane temperature

Vision researchers have investigated the differences between global and local feature perception. No one has, however, examined the role of global and local feature discrimination in sustained attention tasks. In this experiment participants performed a sustained attention task requiring either global or local letter target discriminations or watched the same displays without any work imperative. Reaction time to targets was slower when global feature discriminations were required than when local feature discriminations were required. Tympanic membrane temperature (TMT) was utilized in this study as an index of cerebral activation. Participants in the global letter detection condition had elevated post-task right TMT, indicative of reduced cerebral activation in the right hemisphere, in comparison to participants in the local letter detection or no-work imperative conditions. Both the performance and physiological results of this study indicate increased cognitive fatigue when global feature discriminations are required.     

Time course of visual attention across perceptual levels and objects

Theories of shifts of visual attention based on attentional blink or dwell time do not directly address shifts of attention across different levels (global or local) involving multiple objects. Two experiments were conducted employing the attentional dwell time paradigm to investigate the shifts of visual attention between objects selected at same or different levels. Participants were instructed to identify two successive compound stimuli at a pre-specified level (global or local) presented at two different locations with variable SOA. The initial pair of locations in which the stimulus was presented was fixed in Experiment 1 but not in Experiment 2. Experiment 1 results showed very little impairment for second target identification when both the targets were at the global level. Attentional shift was better with both targets at the same level compared to different levels. Experiment 2 results showed that local followed by global target identification is difficult at short SOAs compared to other conditions. The results indicate that scope of attention affects the time course of visual attention. Global processing could be performed with very little capacity limitation simultaneously with distributed attention. The default mode of attention might be distributed and attention becomes focused for target identification. Different mechanisms may underlie shifts in focused attention between different locations and changes in attentional set required by changes in perceptual levels.     

Body- and environmental-stabilized processing of spatial knowledge

In 5 experiments, the authors examined the perceptual and cognitive processes used to track the locations of objects during locomotion. Participants learned locations of 9 objects on the outer part of a turntable from a single viewpoint while standing in the middle of the turntable. They subsequently pointed to objects while facing the learning heading and a new heading, using imagined headings that corresponded to their current actual body heading and the other actual heading. Participants in 4 experiments were asked to imagine that the objects moved with them as they turned and were shown or only told that the objects would move with them; in Experiment 5, participants were shown that objects could move with them but were asked to ignore this as they turned. Results showed that participants tracked object locations as though the objects moved with them when shown but not when told about the consequences of their locomotion. Once activated, this processing mode could not be suppressed by instructions. Results indicated that people process object locations in a body- or an environment-stabilized manner during locomotion, depending on the perceptual consequences of locomotion.     

The relationship between allocentric and egocentric frames of reference and categorical and coordinate spatial information processing

We report two experiments on the relationship between allocentric/egocentric frames of reference and categorical/coordinate spatial relations. Jager and Postma (2003) suggest two theoretical possibilities about their relationship: categorical judgements are better when combined with an allocentric reference frame and coordinate judgements with an egocentric reference frame (interaction hypothesis); allocentric/egocentric and categorical/coordinate form independent dimensions (independence hypothesis). Participants saw stimuli comprising two vertical bars (targets), one above and the other below a horizontal bar. They had to judge whether the targets appeared on the same side (categorical) or at the same distance (coordinate) with respect either to their body-midline (egocentric) or to the centre of the horizontal bar (allocentric). The results from Experiment 1 showed a facilitation in the allocentric and categorical conditions. In line with the independence hypothesis, no interaction effect emerged. To see whether the results were affected by the visual salience of the stimuli, in Experiment 2 the luminance of the horizontal bar was reduced. As a consequence, a significant interaction effect emerged indicating that categorical judgements were more accurate than coordinate ones, and especially so in the allocentric condition. Furthermore, egocentric judgements were as accurate as allocentric ones with a specific improvement when combined with coordinate spatial relations. The data from Experiment 2 showed that the visual salience of stimuli affected the relationship between allocentric/egocentric and categorical/coordinate dimensions. This suggests that the emergence of a selective interaction between the two dimensions may be modulated by the characteristics of the task.     

Locating targets from imagined perspectives: Comparing labelling with pointing responses

Participants in two experiments adopted imagined perspectives in a perceptually available spatial scene and located targets by using either verbal terms (labelling) or arrows (pointing). Results revealed that performance was faster and more accurate for labelling than for pointing and more so when the adopted perspectives were misaligned with the physical orientation of the participant. This finding was obtained even when an orientation cue allowed participants to adopt the imagined perspective in advance of target presentation. A third experiment replicated these findings using traditional pointing and verbal responding. We argue that performance from misaligned perspectives in perspective-taking tasks suffers due to reference frame conflicts and that these conflicts are more pronounced with pointing and other manual responses that rely more on the reference frame of the physical body.     

Locating targets from imagined perspectives: comparing labelling with pointing responses

Participants in two experiments adopted imagined perspectives in a perceptually available spatial scene and located targets by using either verbal terms (labelling) or arrows (pointing). Results revealed that performance was faster and more accurate for labelling than for pointing and more so when the adopted perspectives were misaligned with the physical orientation of the participant. This finding was obtained even when an orientation cue allowed participants to adopt the imagined perspective in advance of target presentation. A third experiment replicated these findings using traditional pointing and verbal responding. We argue that performance from misaligned perspectives in perspective-taking tasks suffers due to reference frame conflicts and that these conflicts are more pronounced with pointing and other manual responses that rely more on the reference frame of the physical body.