Size Perception Bias and Reach-to-Grasp Kinematics: An Exploratory Study on the Virtual Hand With a Consumer Immersive Virtual-Reality Device

While studies have increasingly used virtual hands and objects in virtual environments to investigate various processes of psychological phenomena, conflicting findings have been reported even at the most basic level of perception and action. To reconcile this situation, the present study aimed 1) to assess biases in size perception of a virtual hand using a strict psychophysical method and 2) to provide firm and conclusive evidence of the kinematic characteristics of reach-to-grasp movements with various virtual effectors (whole hand or fingertips only, with or without tactile feedback of a target object). Experiments were conducted using a consumer immersive virtual reality device. In a size judgment task, participants judged whether a presented virtual hand or an everyday object was larger than the remembered size. The results showed the same amplitude of underestimation (approximately 5%) for the virtual hand and the object, and no influence of object location, visuo-proprioceptive congruency, or short-term experience of controlling the virtual hand. Furthermore, there was a moderate positive correlation between actual hand size and perception bias. Analyses of reach-to-grasp movements revealed longer movement times and larger maximum grip aperture (MGA) for a virtual, as opposed to a physical, environment, but the MGA did not change when grasping was performed without tactile feedback. The MGA appeared earlier in the time course of grasping movements in all virtual reality conditions, regardless of the type of virtual effector. These findings confirm and corroborate previous evidence and may contribute to the field of virtual hand interfaces for interactions with virtual worlds.

The heart rate discrimination task: a psychophysical method to estimate the accuracy and precision of interoceptive beliefs

Interoception - the physiological sense of our inner bodies - has risen to the forefront of psychological and psychiatric research. Much of this research utilizes tasks that attempt to measure the ability to accurately detect cardiac signals. Unfortunately, these approaches are confounded by well-known issues limiting their validity and interpretation. At the core of this controversy is the role of subjective beliefs about the heart rate in confounding measures of interoceptive accuracy. Here, we recast these beliefs as an important part of the causal machinery of interoception, and offer a novel psychophysical “heart rate discrimination” method to estimate their accuracy and precision. By applying this task in 218 healthy participants, we demonstrate that cardiac interoceptive beliefs are more biased, less precise, and are associated with poorer metacognitive insight relative to a matched exteroceptive control. Our task, provided as an open-source python package, offers users an intuitive, robust approach to quantifying cardiac beliefs.HighlightsCurrent interoception tasks conflate cardiac beliefs with accuracy.We introduce a Bayesian method for estimating cardiac belief accuracy and precision.Individuals underestimate their heart rate by −7 BPM (95% CI [−8.6 −5.3]) on average.Cardiac beliefs are associated with reduced precision and metacognitive insight.The task and modelling tools are provided in the Python Cardioception Package.

The points of view and the facts of the psychophysical method. By G. E Müller Wiesbaden. 1904. p. 244

Releasing his work in light, the author set himself the goal of collecting and combining, as far as possible, all theories and foundations of psychophysical methodology, which existed and are being born since Fechner. Not a little attention is paid by the author to bringing in more or less harmonious system of literary sources.

Stimuli Characteristics and Psychophysical Requirements for Visual Training in Amblyopia: A Narrative Review

Active vision therapy using perceptual learning and/or dichoptic or binocular environments has shown its potential effectiveness in amblyopia, but some doubts remain about the type of stimuli and the mode and sequence of presentation that should be used. A search was performed in PubMed, obtaining 143 articles with information related to the stimuli used in amblyopia rehabilitation, as well as to the neural mechanisms implied in such therapeutic process. Visual deficits in amblyopia and their neural mechanisms associated are revised, including visual acuity loss, contrast sensitivity reduction and stereopsis impairment. Likewise, the most appropriate stimuli according to the literature that should be used for an efficient rehabilitation of the amblyopic eye are described in detail, including optotypes, Gabor’s patches, random-dot stimuli and Vernier’s stimuli. Finally, the properties of these stimuli that can be modified during the visual training are discussed, as well as the psychophysical method of their presentation and the type of environment used (perceptual learning, dichoptic stimulation or virtual reality). Vision therapy using all these revised concepts can be an effective option for treating amblyopia or accelerating the treatment period when combining with patching. It is essential to adapt the stimuli to the patient’s individual features in both monocular and binocular training.

Chicken colour discrimination depends on background colour

ABSTRACTHow well can a bird discriminate between two red berries on a green background? The absolute threshold of colour discrimination is set by photoreceptor noise, but animals do not perform at this threshold; their performance can depend on additional factors. In humans and zebra finches, discrimination thresholds for colour stimuli depend on background colour, and thus the adaptive state of the visual system. We have tested how well chickens can discriminate shades of orange or green presented on orange or green backgrounds. Chickens discriminated slightly smaller colour differences between two stimuli presented on a similarly coloured background, compared with a background of very different colour. The slope of the psychometric function was steeper when stimulus and background colours were similar but shallower when they differed markedly, indicating that background colour affects the certainty with which the animals discriminate the colours. The effect we find for chickens is smaller than that shown for zebra finches. We modelled the response to stimuli using Bayesian and maximum likelihood estimation and implemented the psychometric function to estimate the effect size. We found that the result is independent of the psychophysical method used to evaluate the effect of experimental conditions on choice performance.

The power function of the ten test for measuring neural sensitivity in clinical pain or sensory abnormalities

This review highlights a simple psychophysical quantitative sensory testing (QST) method (the ten test) for research and clinical practice as it relates to sensitivity change and symptom improvement in pain populations. This cost-effective QST has a three-fold benefit of being diagnostic, prognostic and providing outcome evaluation. The power function of the ten test is discussed with the theoretical foundation of levels of measurement and psychophysical method that can approach ratio scaling in mind. The ratio level measurement might be useful for the researcher as the normative values of different QSTs are not well established. As a reliable and valid testing method, it provides an option for clinicians in busy clinical settings, and/or where QST equipment is unavailable.