Flexible Use of Spatial Frames of Reference for Object–Location Memory in Older Adults

In memory, representations of spatial features are stored in different reference frames; features relative to our position are stored egocentrically and features relative to each other are stored allocentrically. Accessing these representations engages many cognitive and neural resources, and so is susceptible to age-related breakdown. Yet, recent findings on the heterogeneity of cognitive function and spatial ability in healthy older adults suggest that aging may not uniformly impact the flexible use of spatial representations. These factors have yet to be explored in a precisely controlled task that explicitly manipulates spatial frames of reference across learning and retrieval. We used a lab-based virtual reality task to investigate the relationship between object–location memory across frames of reference, cognitive status, and self-reported spatial ability. Memory error was measured using Euclidean distance from studied object locations to participants’ responses at testing. Older adults recalled object locations less accurately when they switched between frames of reference from learning to testing, compared with when they remained in the same frame of reference. They also showed an allocentric learning advantage, producing less error when switching from an allocentric to an egocentric frame of reference, compared with the reverse direction of switching. Higher MoCA scores and better self-assessed spatial ability predicted less memory error, especially when learning occurred egocentrically. We suggest that egocentric learning deficits are driven by difficulty in binding multiple viewpoints into a coherent representation. Finally, we highlight the heterogeneity of spatial memory performance in healthy older adults as a potential cognitive marker for neurodegeneration, beyond normal aging.

Individuals use different spatial reference frames on different axes: Evidence from indigenous Amazonians

The physical properties of space may be universal, but the way people conceptualize space is variable. In some groups, people tend to use egocentric space (e.g. left, right) to encode the locations of objects, while in other groups, people encode the same spatial scene using allocentric space (e.g. upriver, downriver). These different spatial frames of reference (FoRs) characterize the way people talk about spatial relations and the way they think about them, even when they are not using language. Although spatial language and spatial reasoning tend to covary, the root causes of this variation are unclear. Here we propose that variation in FoR use partly reflects the discriminability of the relevant spatial continua. In an initial test of this proposal in a group of indigenous Bolivians, we compared FoR use across spatial axes that are known to differ in discriminability. In both verbal and nonverbal tests, participants spontaneously used different FoRs on different spatial axes: On the lateral axis, where egocentric (left-right) discrimination is difficult, their spatial behavior and language was predominantly allocentric; on the sagittal axis, where egocentric (front-back) discrimination is relatively easy, they were predominantly egocentric. These findings challenge the claim that each language group can be characterized by a predominant spatial frame of reference. Rather, both spatial memory and language can differ categorically across axes, even within the same individuals. We suggest that differences in spatial discrimination can explain differences in both spatial memory and language within and across human groups.

Looking at Islamic Patterns II: Making Sense of Geometry

Islamic geometric patterns are arrangements of interlocking stars and polygons. Why do they attract our attention? Following Silvia's model, interesting stimuli are hard to process yet comprehensible. To understand what it means to make sense of a geometric pattern we explore representations of space and geometric structure. Perceptual and linguistic evidence yields small sets of primitive objects and qualitative relations that suffice to build a synthetic geometry of perceptual space; constructing patterns requires the capability to divide lines and circles into equal parts, but does not rely on measuring lengths or angles explicitly.We compare eight representations of a star motif that demonstrate different approaches, different spatial frames of reference, and different levels of abstraction. A representation may be parametrised to represent a category, which allows us to verify that it captures salient features (the object should not be an anomaly in the category). We conclude that sequential constructive representations (algorithms) do not provide a good model for spatial structure, and that compression (encoding) and comprehension (making sense) are distinct.Chunking and schemas capture generic structure in unfamiliar contexts, in particular repetitive, composite, modular and hierarchical structure. The large corpus of Islamic patterns exhibits constant innovation over hundreds of years. We give examples to illustrate a clear trend towards increasingly complex structure, of both modular and hierarchical forms.

Multirobot Confidence and Behavior Modeling: An Evaluation of Semiautonomous Task Performance and Efficiency

There is considerable interest in multirobot systems capable of performing spatially distributed, hazardous, and complex tasks as a team leveraging the unique abilities of humans and automated machines working alongside each other. The limitations of human perception and cognition affect operators’ ability to integrate information from multiple mobile robots, switch between their spatial frames of reference, and divide attention among many sensory inputs and command outputs. Automation is necessary to help the operator manage increasing demands as the number of robots (and humans) scales up. However, more automation does not necessarily equate to better performance. A generalized robot confidence model was developed, which transforms key operator attention indicators to a robot confidence value for each robot to enable the robots’ adaptive behaviors. This model was implemented in a multirobot test platform with the operator commanding robot trajectories using a computer mouse and an eye tracker providing gaze data used to estimate dynamic operator attention. The human-attention-based robot confidence model dynamically adapted the behavior of individual robots in response to operator attention. The model was successfully evaluated to reveal evidence linking average robot confidence to multirobot search task performance and efficiency. The contributions of this work provide essential steps toward effective human operation of multiple unmanned vehicles to perform spatially distributed and hazardous tasks in complex environments for space exploration, defense, homeland security, search and rescue, and other real-world applications.

Variation in spatial concepts: Different frames of reference on different axes

Spatial language and cognition vary across contexts. In some groups, people tend to use egocentric space (e.g. left, right) to encode the locations of objects, while in other groups, people use allocentric space (e.g. upriver, downriver) to describe the same spatial scene. These different spatial Frames of Reference (FoRs) characterize both the way people talk about spatial relations and the way they think about them, even when they are not using language. These patterns of spatial language and spatial thinking tend to covary, but the root causes of this variation are unclear. Here we propose that this variation in FoR use reflects variation in the spatial discriminability of the relevant spatial continua. In an initial test of this proposal, we compared FoR use across spatial axes that are known to differ in discriminability. In two non-verbal tests, a group of indigenous Bolivians used different FoRs on different spatial axes; on the lateral axis, where egocentric (left-right) discrimination is difficult, their behavior was predominantly allocentric; on the sagittal axis, where egocentric (front-back) discrimination is relatively easy, their behavior was predominantly egocentric. These findings support the spatial discriminability hypothesis, which may explain variation in spatial concepts not only across axes, but also across groups, between individuals, and over development.

Mild Stroke Affects Pointing Movements Made in Different Frames of Reference

Background Motor performance is a complex process controlled in task-specific spatial frames of reference (FRs). Movements can be made within the framework of the body (egocentric FR) or external space (exocentric FR). People with stroke have impaired reaching, which may be related to deficits in movement production in different FRs. Objective To characterize rapid motor responses to changes in the number of degrees of freedom for movements made in different FRs and their relationship with sensorimotor and cognitive impairment in individuals with mild chronic stroke. Methods Healthy and poststroke individuals moved their hand along the contralateral forearm (egocentric task) and between targets in the peripersonal space (exocentric task) without vision while flexing the trunk. Trunk movement was blocked in randomized trials. Results For the egocentric task, controls produced the same endpoint trajectories in both conditions (free- and blocked-trunk) by preserving similar shoulder-elbow interjoint coordination (IJC). However, endpoint trajectories were dissimilar because of altered IJC in stroke. For the exocentric task, controls produced the same endpoint trajectories when the trunk was free or blocked by rapidly changing the IJC, whereas this was not the case in stroke. Deficits in exocentric movement after stroke were related to cognitive but not sensorimotor impairment. Conclusions Individuals with mild stroke have deficits rapidly responding to changing conditions for complex reaching tasks. This may be related to cognitive deficits and limitations in the regulation of tonic stretch reflex thresholds. Such deficits should be considered in rehabilitation programs encouraging the reintegration of the affected arm into activities of daily living.

Space as space and space as grammar

Research on narratives in an Australian language demonstrated surprising facts about speakers’ spatial orientation and knowledge both in the insistent use of morphologically hypertrophied spoken directional terminology and in accompanying gestures. Pursuing comparable phenomena in a Mayan language from the other side of the globe revealed correspondingly complex gestural devices for communicating about location and direction but with very different kinds of support from speech. Evidence from a new sign language, emerging in the same Mayan context, suggests that mechanisms for signing about space both resemble and depart from the gestural practices of the surrounding speech community. In particular, they invoke spatial “frames of reference” not used by speakers to sign about location and direction, and they employ signed “spatial grammar” to express syntactic argument structure.

From the field into the lab: Causal approaches to the evolution of spatial language

There is striking variation in preferences for specific spatial linguistic strategies among different speech communities. Increasing evidence now suggests that this might not simply be a result of neutral drift, but rather a form of linguistic adaptation to the local social, cultural, or physical environment. Recent studies indicate that different factors like, e.g., topography, subsistence style, or bilingualism successfully predict the choice of spatial Frames of Reference (FoR) on linguistic and non-linguistic tasks. However, the exact causal relationships between these variables and the cultural evolutionary mechanisms that lead to selection of one FoR strategy over another are still not fully understood. In this paper, we argue that in order to arrive at a more mechanistic and causal understanding of the cultural evolution of spatial language, observations from descriptive fieldwork should be combined with experimental and computational methods. In such a framework, causal relationships between linguistic and non-linguistic variables (such as topography and FoR choice) can be isolated and empirically tested in order to shed light on how sociotopographic factors motivate the variation in spatial language we observe cross-linguistically.