T. Schürmann

Human body schema exploration: Analyzing design requirements of Robotic Hand and Leg Illusions

Understanding the integration of user-proximal robots in the body schema of their human users has a distinct potential to improve human-robot interaction. Robotic devices can help to investigate the psychological fundamentals of body schema integration. While the Rubber Hand Illusion experiment indicates how artifacts can be perceived as a part of the own body, it relies on a passive limb that does not perform motions during the examinations. Novel setups aim at Robotic Hand/Leg Illusions induced by robotic devices which imitate human motions. Although such devices distinctly extend experimental possibilities, their design is rather proprietary and unstructured up to now. This paper analyzes the requirements of robotic hand and leg illusion setups based on systematic discussion of a multidisciplinary team of researchers from engineering and psychology. In a comparative study, requirements are collected and structured, their similarities and differences are determined, and the most important ones are extracted yielding design implications. The requirements with the highest priority are setup characteristics that concern the occurrence and quality of the illusion, i.e., hiding the real limb, anatomical plausibility, visual appearance, temporal delay, and software-controlled experimental conditions. Based on the results, the design of future robotic devices for the exploration of human body schema integration might be guided and supported.

Exploration of lower limb body schema integration with respect to body-proximal robotics

The integration of body-proximal robots into the body schema of their users is a crucial aspect for the acceptance of those artificial devices. Humans integrate information about such systems from visual, tactile, and proprioceptive perception. For the design of novel, human-oriented robotics, it is important to understand how this integration can be supported by the technical design of the robot. In this paper, first experiments aiming at the assessment of lower limb body schema integration during postural motions are performed. A robot is used to imitate the squatting movements of human subjects. In contrast to a previous implementation, human motion sensing is improved for real-time operation by using inertial measurement units. A first human-in-the-loop experiment indicates that this approach resolves limitations caused by delays of the previous RGB-D measurements. The integration into the body schema of the participants is assessed by means of a psychometric questionnaire. Experimental results regarding body schema integration suggest that for body-proximal robotics noticeably detached from human subjects, agency is the most stable of body schema variables and that to induce a sense of ownership and location, more feedback channels to the subjects might be required.

Theoretical implementation of prior knowledge in the design of a multi-scale prosthesis satisfaction questionnaire

BackgroundIn product development for lower limb prosthetic devices, a set of special criteria needs to be met. Prosthetic devices have a direct impact on the rehabilitation process after an amputation with both perceived technological and psychological aspects playing an important role. However, available psychometric questionnaires fail to consider the important links between these two dimensions. In this article a probabilistic latent trait model is proposed with seven technical and psychological factors which measure satisfaction with the prosthesis. The results of a first study are used to determine the basic parameters of the statistical model. These distributions represent hypotheses about factor loadings between manifest items and latent factors of the proposed psychometric questionnaire.MethodsA study was conducted and analyzed to form hypotheses for the prior distributions of the questionnaire’s measurement model. An expert agreement study conducted on 22 experts was used to determine the prior distribution of item-factor loadings in the model.ResultsModel parameters that had to be specified as part of the measurement model were informed prior distributions on the item-factor loadings. For the current 70 items in the questionnaire, each factor loading was set to represent the certainty with which experts had assigned the items to their respective factors. Considering only the measurement model and not the structural model of the questionnaire, 70 out of 217 informed prior distributions on parameters were set.ConclusionThe use of preliminary studies to set prior distributions in latent trait models, while being a relatively new approach in psychological research, provides helpful information towards the design of a seven factor questionnaire that means to identify relations between technical and psychological factors in prosthetic product design and rehabilitation medicine.

Movement transformation on multi-touch devices: Intuition or instructional preparation?

Multi-touch technology is a key part of computer interaction today, yet little is known about the distinction between direct and indirect input devices in terms of intuitive interaction. An experimental study aims to identify the difficulties of interaction with indirect multi-touch devices by applying the action regulation theory and the principle of movement transformation to common computer tasks involving gesture utilization. An analysis of the data acquired from 54 subjects working with an Apple Magic Trackpad implies that gestures on indirect multi-touch devices are not utilized intuitively without instructions that bypass conceptual difficulties of indirect gesture usage. It is shown that gesture use influences product assessment measured by User Experience questionnaires and that prior experience with direct multi-touch devices does not influence gesture usage or product assessment. We advise that product developers utilize video instructions to create a sense of intuitive interaction.