Dynamic Corridor Illusion in Pigeons: Humanlike Pictorial Cue Precedence Over Motion Parallax Cue in Size Perception

Depth information is necessary for perceiving the real size of objects at varying visual distances. To investigate to what extent this size constancy present in another vertebrate class, we addressed the two questions using pigeons: (a) whether pigeons see a corridor illusion based on size constancy and (b) whether pigeons prioritize pictorial cues over motion parallax cues for size constancy, like humans. We trained pigeons to classify target sizes on a corridor. In addition, we presented a dynamic version of corridor illusion in which the target and corridor moved side by side. Target speed was changed to manipulate motion parallax. With the static corridor, pigeons overestimated the target size when it was located higher, indicating that pigeons see a corridor illusion like humans. With the dynamic corridor, the pigeons overestimated the target size depending on target position, as in the static condition, but target speed did not affect their responses, indicating that the pictorial precedence also applies to pigeons. In a follow-up experiment using the same stimulus, we confirmed that humans perceive object size based on pictorial cues. These results suggest that size constancy characteristics are highly similar between pigeons and humans, despite the differences in their phylogeny and neural systems

Effects of Avatar Hand-size Modifications on Size Judgments of Familiar and Abstract Objects in Virtual Reality

University of Minnesota M.S. thesis.June 2019. Major: Computer Science. Advisor: Peter Willemsen. 1 computer file (PDF); vii, 56 pages.Many research studies have investigated spatial understanding within virtual envi- ronments, ranging from distance estimation, size judgments, and perception of scale. Eventually, this knowledge will help us to create virtual environments that better match our spatial abilities within natural environments. To further understand how people interpret the size of virtual objects, we present an experiment that utilizes a proprioceptive-based size estimation measure designed to elicit a three-dimensional judgment of an object’s size using a box-sizing task. Participants viewed both ab- stract and familiar objects presented within action-space in a virtual environment and were asked to make an axis-aligned box the same size as the object they previously observed. A between-subjects manipulation modified a participant’s avatar hand size to be either 80%, 100% or 120% of their measured hand size. Results indicate that the avatar hand size manipulation scales various factors of these size judgments in the three dimensions. Additionally, whether an object was abstract or a familiar size object produced distinctly different size judgments

Virtual reality obstacle crossing: adaptation, retention and transfer to the physical world

Virtual reality (VR) paradigms are increasingly being used in movement and exercise sciences with the aim to enhance motor function and stimulate motor adaptation in healthy and pathological conditions. Locomotor training based in VR may be promising for motor skill learning, with transfer of VR skills to the physical world in turn required to benefit functional activities of daily life. This PhD project aims to examine locomotor adaptations to repeated VR obstacle crossing in healthy young adults as well as transfers to the untrained limb and the physical world, and retention potential of the learned skills. For these reasons, the current thesis comprises three studies using controlled VR obstacle crossing interventions during treadmill walking. In the first and second studies we investigated adaptation to crossing unexpectedly appearing virtual obstacles, with and without feedback about crossing performance, and its transfer to the untrained leg. In the third study we investigated transfer of virtual obstacle crossing to physical obstacles of similar size to the virtual ones, that appeared at the same time point within the gait cycle. We also investigated whether the learned skills can be retained in each of the environments over one week. In all studies participants were asked to walk on a treadmill while wearing a VR headset that represented their body as an avatar via real-time synchronised optical motion capture. Participants had to cross virtual and/or physical obstacles with and without feedback about their crossing performance. If applicable, feedback was provided based on motion capture immediately after virtual obstacle crossing. Toe clearance, margin of stability, and lower extremity joint angles in the sagittal plane were calculated for the crossing legs to analyse adaptation, transfer, and retention of obstacle crossing performance. The main outcomes of the first and second studies were that crossing multiple virtual obstacles increased participants’ dynamic stability and led to a nonlinear adaptation of toe clearance that was enhanced by visual feedback about crossing performance. However, independent of the use of feedback, no transfer to the untrained leg was detected. Moreover, despite significant and rapid adaptive changes in locomotor kinematics with repeated VR obstacle crossing, results of the third study revealed limited transfer of learned skills from virtual to physical obstacles. Lastly, despite full retention over one week in the virtual environment we found only partial retention when crossing a physical obstacle while walking on the treadmill. In summary, the findings of this PhD project confirmed that repeated VR obstacle perturbations can effectively stimulate locomotor skill adaptations. However, these are not transferable to the untrained limb irrespective of enhanced awareness and feedback. Moreover, the current data provide evidence that, despite significant adaptive changes in locomotion kinematics with repeated practice of obstacle crossing under VR conditions, transfer to and retention in the physical environment is limited. It may be that perception-action coupling in the virtual environment, and thus sensorimotor coordination, differs from the physical world, potentially inhibiting retained transfer between those two conditions. Accordingly, VR-based locomotor skill training paradigms need to be considered carefully if they are to replace training in the physical world

鳥類から探る奥行き・運動視進化の比較認知科学的検討

京都大学新制・課程博士博士(文学)甲第22924号文博第870号新制||文||704(附属図書館)京都大学大学院文学研究科行動文化学専攻(主査)准教授 黒島 妃香, 教授 蘆田 宏, 教授 西田 眞也学位規則第4条第1項該当Doctor of LettersKyoto UniversityDFA

Age-related changes in memory for object locations across different perspectives.

One important aspect of spatial cognition is the ability to recognize and remember spatial locations across different viewpoints. Previous research has suggested that those abilities decline in older adults. The aim of the current PhD project is to develop a clearer understanding of what may be contributing to age-related declines in recognising object locations from different perspectives. Specifically, focusing on how ageing effects encoding strategies that are used to memorize spatial configurations and the precision with which object/landmark locations are remembered. In Chapter 2, gaze behaviour was recorded during a task in which young and older adults judged whether previously encoded objects have remained in the same position or were displaced following perspective shifts. Ageing was associated with declines in spatial processing abilities. Additionally, older adults displayed a more conservative decision style and relied more on encoding object positions using room-based cues compared to young adults, who focused on the spatial relations among the to-be remembered objects during encoding. In Chapter 3, age-related differences in encoding strategies were further investigated using a modified version of the task used in Chapter 2 in which the availability and utility of the room- based cues was manipulated. Performance accuracy was similar across both age groups, yet, older adults displayed a greater preference towards a more categorical encoding strategy in which they formed spatial relations between objects and room-based cues. In the remaining chapters the focus shifted to investigating the precision with which object locations are remembered across different perspectives. In Chapter 4 participants memorized the position of an object in a virtual room and then judged from a different perspective, whether the object has moved to the left or to the right. Results revealed that participants exhibited a systematic bias in their responses that was termed the reversed congruency effect. Specifically, participants performed worse when the camera and the object moved in the same direction than when they moved in opposite directions. In Experiment 2, it was shown that the presence of additional objects in the environment reduced the reversed congruency effect whilst in Experiment 3 the reversed congruency effect was greater in older adults, suggesting that the quality of spatial memory and perspective-taking abilities are critical in mediating the reversed congruency effect. In Chapter 5, a novel task was used to investigate the systematic bias reported in Chapter 4. In this task participants encoded the position of an object in a virtual room and then estimated the object’s position following a perspective shift. In addition, memory load was manipulated. Overall, participants systematically overestimated the position of the object in the direction of the perspective shift. This bias was present in both memory and perception conditions. In Chapter 6, these results were replicated in an online-based version of the study. Lastly in Chapter 7, the influence of camera translations and camera rotations on the perspective shift related bias was decoupled. Additionally, the study investigated whether adding more information into the scene would reduce the bias and if there are age-related differences in the precision of object location estimates and the tendency to display the bias related to perspective shift. Overall, camera translations led to a greater systematic bias than camera rotations. Furthermore, the use of additional spatial information improved the precision with which object locations were estimated and reduced the bias associated with camera translation. Finally, although older adults were as precise as younger participants when estimating object locations, they benefited less from additional spatial information and their responses were more biased in the direction of camera translations. Overall, by combining eye-tracking and diffusion modelling the current thesis shows that ageing is associated with changes in the type of information that is used to encode object locations across different perspectives. Additionally, ageing was found to be particularly associated with impairments in the formation of fine-grained spatial representations. Furthermore, a novel bias in spatial memory across different perspectives has been identified. It is proposed that the perspective shift related bias is driven by uncertainty about object position following a perspective shift that leads participants to rely on an egocentric anchor when estimating the location of an object