Matthew G. Buckley

Shape Shifting: Local Landmarks Interfere With Navigation by, and Recognition of, Global Shape

An influential theory of spatial navigation states that the boundary shape of an environment is preferentially encoded over and above other spatial cues, such that it is impervious to interference from alternative sources of information. We explored this claim with 3 intradimensional–extradimensional shift experiments, designed to examine the interaction of landmark and geometric features of the environment in a virtual navigation task. In Experiments 1 and 2, participants were first required to find a hidden goal using information provided by the shape of the arena or landmarks integrated into the arena boundary (Experiment 1) or within the arena itself (Experiment 2). Participants were then transferred to a different-shaped arena that contained novel landmarks and were again required to find a hidden goal. In both experiments, participants who were navigating on the basis of cues that were from the same dimension that was previously relevant (intradimensional shift) learned to find the goal significantly faster than participants who were navigating on the basis of cues that were from a dimension that was previously irrelevant (extradimensional shift). This suggests that shape information does not hold special status when learning about an environment. Experiment 3 replicated Experiment 2 and also assessed participants’ recognition of the global shape of the navigated arenas. Recognition was attenuated when landmarks were relevant to navigation throughout the experiment. The results of these experiments are discussed in terms of associative and non-associative theories of spatial learning.

Learned predictiveness training modulates biases towards using boundary or landmark cues during navigation

A number of navigational theories state that learning about landmark information should not interfere with learning about shape information provided by the boundary walls of an environment. A common test of such theories has been to assess whether landmark information will overshadow, or restrict, learning about shape information. Whilst a number of studies have shown that landmarks are not able to overshadow learning about shape information, some have shown that landmarks can, in fact, overshadow learning about shape information. Given the continued importance of theories that grant the shape information that is provided by the boundary of an environment a special status during learning, the experiments presented here were designed to assess whether the relative salience of shape and landmark information could account for the discrepant results of overshadowing studies. In Experiment 1, participants were first trained that either the landmarks within an arena (landmark-relevant), or the shape information provided by the boundary walls of an arena (shape-relevant), were relevant to finding a hidden goal. In a subsequent stage, when novel landmark and shape information were made relevant to finding the hidden goal, landmarks dominated behaviour for those given landmark-relevant training, whereas shape information dominated behaviour for those given shape-relevant training. Experiment 2, which was conducted without prior relevance training, revealed that the landmark cues, unconditionally, dominated behaviour in our task. The results of the present experiments, and the conflicting results from previous overshadowing experiments, are explained in terms of associative models that incorporate an attention variant.

Evidence for spatial navigational impairments in hydrocephalus patients without spina bifida

The cognitive sequelae of hydrocephalus have mostly been explored with standardised clinical tasks. The aim of the present research was determine whether impairments on these abstract tasks extend to everyday spatial and navigational behaviour. Patients with hydrocephalus, but without spina bifida, were compared to a control group on tests of searching behaviour, landmark memory, route learning, and path integration. Participants with hydrocephalus displayed reduced sensitivity to spatial cueing, less accurate route-learning, and significantly less accurate spatial updating. These data represent an important empirical demonstration of spatial navigational impairments due to hydrocephalus outside of the context of spina bifida. We discuss some of the cognitive, neural, and individual differences factors that might contribute to this particular pattern of impairments.

Spatial navigational impairments in hydrocephalus

Whilst much is known about the neuropathological consequences of hydrocephalus, there have been comparatively few studies of the cognitive impairments associated with it. Studies using standardised tests of cognitive function have identified a general pattern of impairments, with patients exhibiting particular difficulty on tests of spatial memory and executive function. A strong prediction is that these deficits are likely to affect daily wayfinding behaviour, and we report a study of spatial and navigational abilities in a group of patients with hydrocephalus but without spina bifida. Participants completed a range of experimental tasks assessing spatial cueing behaviour, landmark memory and route-learning, and idiothetic path integration. This patient group was compared to a control sample matched on verbal, spatial, and intelligence measures, and hydrocephalus was found to be associated with relative impairments in each of the tasks. Patients exhibited reduced sensitivity to spatial cueing, less accurate route-learning, poorer memory for landmark objects, and less accurate spatial updating (with particular impairments in the calculation of heading). Overall, these data represent the first empirical demonstration of navigational impairments in hydrocephalus, and we suggest some of the cognitive, neural, and individual differences factors that may contribute to the pattern of performance reported.

Blocking Spatial Navigation Across Environments That Have a Different Shape

According to the geometric module hypothesis, organisms encode a global representation of the space in which they navigate, and this representation is not prone to interference from other cues. A number of studies, however, have shown that both human and non-human animals can navigate on the basis of local geometric cues provided by the shape of an environment. According to the model of spatial learning proposed by Miller and Shettleworth (2007, 2008), geometric cues compete for associative strength in the same manner as non-geometric cues do. The experiments reported here were designed to test if humans learn about local geometric cues in a manner consistent with the Miller-Shettleworth model. Experiment 1 replicated previous findings that humans transfer navigational behavior, based on local geometric cues, from a rectangle-shaped environment to a kite-shaped environment, and vice versa. In Experiments 2 and 3, it was observed that learning about non-geometric cues blocked, and were blocked by, learning about local geometric cues. The reciprocal blocking observed is consistent with associative theories of spatial learning; however, it is difficult to explain the observed effects with theories of global-shape encoding in their current form.

Thinking outside of the box: Transfer of shape-based reorientation across the boundary of an arena.

The way in which human and non-human animals represent the shape of their environments remains a contentious issue. According to local theories of shape learning, organisms encode the local geometric features of the environment that signal a goal location. In contrast, global theories of shape learning suggest that organisms encode the overall shape of the environment. There is, however, a surprising lack of evidence to support this latter claim, despite the fact that common behaviours seem to require encoding of the global-shape of an environment. We tested one such behaviour in 5 experiments, in which human participants were trained to navigate to a hidden goal on one side of a virtual arena (e.g. the inside) before being required to find the same point on the alternative side (e.g. the outside). Participants navigated to the appropriate goal location, both when inside and outside the virtual arena, but only when the shape of the arena remained the same between training and test (Experiments 1a and 1b). When the arena shape was transformed between these stages, participants were lost (Experiments 2a and 2b). When training and testing was conducted on the outside of two different-shaped arenas that shared local geometric cues participants once again explored the appropriate goal location (Experiment 3). These results provide core evidence that humans encode a global representation of the overall shape of the environments in, or around, which they navigate.

The Developmental Trajectory of Intramaze and Extramaze Landmark Biases in Spatial Navigation: An Unexpected Journey

Adults learning to navigate to a hidden goal within an enclosed space have been found to prefer information provided by the distal cues of an environment, as opposed to proximal landmarks within the environment. Studies with children, however, have shown that 5- or 7-year-olds do not display any preference toward distal or proximal cues during navigation. This suggests that a bias toward learning about distal cues occurs somewhere between the age of 7 years and adulthood. We recruited 5- to 11-year-old children and an adult sample to explore the developmental profile of this putative change. Across a series of 3 experiments, participants were required to navigate to a hidden goal in a virtual environment, the location of which was signaled by both extramaze and intramaze landmark cues. During testing, these cues were placed into conflict to assess the search preferences of participants. Consistent with previously reported findings, adults were biased toward using extramaze information. However, analysis of the data from children, which incorporated age as a continuous variable, suggested that older children in our sample were, in fact, biased toward using the intramaze landmark in our task. These findings suggest the bias toward using distal cues in spatial navigation, frequently displayed by adults, may be a comparatively late developing trait, and one that could supersede an initial developmental preference for proximal landmarks.

Walking through doorways differentially affects recall and familiarity.

Previous research has reported that walking through a doorway to a new location makes memory for objects and events experienced in the previous location less accurate. This effect, termed the location updating effect, has been used to suggest that location changes are used to mark boundaries between events in memory: memories for objects encountered within the current event are more available than those from beyond an event boundary. Within a computer-generated memory task, participants navigated through virtual rooms, walking through doorways, and interacting with objects. The accuracy and their subjective experience of their memory for the objects (remember/know and confidence) were assessed. The findings showed that shifts in location decreased accurate responses associated with the subjective experience of remembering but not those associated with the experience of knowing, even when considering only the most confident responses in each condition. These findings demonstrate that a shift in location selectively impacts recollection and so contributes to our understanding of boundaries in event memory.