Statistical Analysis with Missing Data

In this paper, I address the question as to why participants tend to respond realistically to situations and events portrayed within an immersive virtual reality system. The idea is put forward, based on the experience of a large number of experimental studies, that there are two orthogonal components that contribute to this realistic response. The first is ‘being there’, often called ‘presence’, the qualia of having a sensation of being in a real place. We call this place illusion (PI). Second, plausibility illusion (Psi) refers to the illusion that the scenario being depicted is actually occurring. In the case of both PI and Psi the participant knows for sure that they are not ‘there’ and that the events are not occurring. PI is constrained by the sensorimotor contingencies afforded by the virtual reality system. Psi is determined by the extent to which the system can produce events that directly relate to the participant, the overall credibility of the scenario being depicted in comparison with expectations. We argue that when both PI and Psi occur, participants will respond realistically to the virtual reality.

/pdf/place-illusion-and-plausibility-can-lead-to-realistic-1hpdya0yai.pdf

Place Illusion and Plausibility Can Lead to Realistic Behaviour in Immersive Virtual Environments

This is a review of the proprioceptive senses generated as a result of our own actions. They include the senses of position and movement of our limbs and trunk, the sense of effort, the sense of force, and the sense of heaviness. Receptors involved in proprioception are located in skin, muscles, and joints. Information about limb position and movement is not generated by individual receptors, but by populations of afferents. Afferent signals generated during a movement are processed to code for endpoint position of a limb. The afferent input is referred to a central body map to determine the location of the limbs in space. Experimental phantom limbs, produced by blocking peripheral nerves, have shown that motor areas in the brain are able to generate conscious sensations of limb displacement and movement in the absence of any sensory input. In the normal limb tendon organs and possibly also muscle spindles contribute to the senses of force and heaviness. Exercise can disturb proprioception, and this has implications for musculoskeletal injuries. Proprioceptive senses, particularly of limb position and movement, deteriorate with age and are associated with an increased risk of falls in the elderly. The more recent information available on proprioception has given a better understanding of the mechanisms underlying these senses as well as providing new insight into a range of clinical conditions.

The Proprioceptive Senses: Their Roles in Signaling Body Shape, Body Position and Movement, and Muscle Force

When we look at our hands, we immediately know that they are part of our own body. This feeling of ownership of our limbs is a fundamental aspect of self-consciousness. We have studied the neuronal counterparts of this experience. A perceptual illusion was used to manipulate feelings of ownership of a rubber hand presented in front of healthy subjects while brain activity was measured by functional magnetic resonance imaging. The neural activity in the premotor cortex reflected the feeling of ownership of the hand. This suggests that multisensory integration in the premotor cortex provides a mechanism for bodily self-attribution.

https://science.sciencemag.org/content/sci/305/5685/875.full.pdf

That's My Hand! Activity in Premotor Cortex Reflects Feeling of Ownership of a Limb

Watching a rubber hand being stroked, while one's own unseen hand is synchronously stroked, may cause the rubber hand to be attributed to one's own body, to "feel like it's my hand." A behavioral measure of the rubber hand illusion (RHI) is a drift of the perceived position of one's own hand toward the rubber hand. The authors investigated (a) the influence of general body scheme representations on the RHI in Experiments 1 and 2 and (b) the necessary conditions of visuotactile stimulation underlying the RHI in Experiments 3 and 4. Overall, the results suggest that at the level of the process underlying the build up of the RHI, bottom-up processes of visuotactile correlation drive the illusion as a necessary, but not sufficient, condition. Conversely, at the level of the phenomenological content, the illusion is modulated by top-down influences originating from the representation of one's own body.

http://www.pc.rhul.ac.uk/sites/lab/wp-content/uploads/2011/12/Tsakiris-Haggard-JEPHPP_2005.pdf

The Rubber Hand Illusion Revisited: Visuotactile Integration and Self-Attribution.

Most organisms facing a choice between multiple stimuli will look repeatedly at them, presumably implementing a comparison process between the items' values. Little is known about the nature of the comparison process in value-based decision-making or about the role of visual fixations in this process. We created a computational model of value-based binary choice in which fixations guide the comparison process and tested it on humans using eye-tracking. We found that the model can quantitatively explain complex relationships between fixation patterns and choices, as well as several fixation-driven decision biases.

Visual fixations and the computation and comparison of value in simple choice

Subjects perceived touch sensations as arising from a table (or a rubber hand) when both the table (or the rubber hand) and their own real hand were repeatedly tapped and stroked in synchrony with the real hand hidden from view. If the table or rubber hand was then 'injured', subjects displayed a strong skin conductance response (SCR) even though nothing was done to the real hand. Sensations could even be projected to anatomically impossible locations. The illusion was much less vivid, as indicated by subjective reports and SCR, if the real hand was simultaneously visible during stroking, or if the real hand was hidden but touched asynchronously. The fact that the illusion could be significantly diminished when the real hand was simultaneously visible suggests that the illusion and associated SCRs were due to perceptual assimilation of the table (or rubber hand) into one's body image rather than associative conditioning. These experiments demonstrate the malleability of body image and the brain's remarkable capacity for detecting statistical correlations in the sensory input.

/pdf/projecting-sensations-to-external-objects-evidence-from-skin-4k4nk4ojcr.pdf

Projecting sensations to external objects: evidence from skin conductance response

Is disaggregation the holy grail of energy efficiency? The case of electricity

Several decision-making models predict that it should be possible to affect real binary choices by manipulating the relative amount of visual attention that decision-makers pay to the two alternatives. We present the results of three behavioral experiments testing this prediction. Visual attention is controlled by manipulating the amount of time subjects fixate on the two items. The manipulation has a differential impact on appetitive and aversive items. Appetitive items are 6 to 11% more likely to be chosen in the long fixation condition. In contrast, aversive items are 7% less likely to be chosen in the long fixation condition. The effect is present for primary goods, such as foods, and for higher-order durable goods, such as posters.

/pdf/biasing-simple-choices-by-manipulating-relative-visual-2zsjwnvih6.pdf

Biasing simple choices by manipulating relative visual attention

Real-time information feedback delivered via technology has been reported to produce up to 20 percent declines in residential energy consumption. There are however large differences in estimates of the effect of real-time feedback technologies on energy use. In this study, we conduct a field experiment to obtain an estimate of the impact of a real-time feedback technology. Access to feedback leads to an average reduction in household electricity consumption of 5.7 percent. Significant declines persist for up to four weeks. In examining time of day reduction effects, we find that the largest reductions were observed initially at all times of the day but as time passes, morning and evening intervals show larger reductions. We find no convincing evidence that household characteristics explain heterogeneity in our treatment effects; we examine demographics, housing characteristics and psychological variables.

K. Carrie Armel

Papers

Visual fixations and the computation and comparison of value in simple choice

Projecting sensations to external objects: evidence from skin conductance response

Is disaggregation the holy grail of energy efficiency? The case of electricity

Biasing simple choices by manipulating relative visual attention

Real-time Feedback and Electricity Consumption: A Field Experiment Assessing the Potential for Savings and Persistence