Biology subjects

Arnold, D. H.

Publications and source records attributed to Arnold, D. H..

13 recordsLinked to original sources

bioRxiv2025

People report having consistent idiosyncratic diets of imagined sensations when they re-experience the past, and pre-experience the future

To some extent, humans can re-experience the sensations of past events and pre-experience the future. These capacities are inter-related. But there are substantial individual differences. At the extremes, small minorities of people report that they either cannot have imagined experiences at all, or that their imagined sensations are as real to them as their actual experiences of the physical world. We wanted to know if such individual differences are uniform across different types of imagined experience (e.g. vision, audio, taste and smell), or if people generally have idiosyncratic patterns of different types (vision, audio, taste and smell) of imagined experiences. We find that people report having idiosyncratic diets of different types of imagined sensation, characterised by differences in salience. One person might have more salient imagined visual than taste experiences, while another reports the reverse. Moreover, these propensities are consistent across peoples attempts to re-experience the past, and to pre-experience the future, and they predict peoples experience and usage of different types of imagined sensation in their everyday lives.

neuroscience↗

bioRxiv2025

Vividness of mental imagery is a broad trait measure of internally generated visual experiences

Research on mental visual imagery typically relies on vividness ratings. However, vividness is ill-defined as it lacks an objective reference. Here, we present survey results that suggest vividness is nevertheless a robust measure. It explains individual differences of a broad range of subjective experiences, from the detail of mental imagery, the propensity to report having other internally generated visual experiences, and the vividness of visual dreams. Critically, simple vividness ratings can replace the protracted questionnaires commonly used for this purpose and reduce methodological issues with these instruments. We further find that vividness is closely linked with the experience of "seeing" mental images or projecting them into the external world. People who report seeing mental images with their eyes shut are also more likely to experience externally projected imagery. Nevertheless, many people report having mental depictions but without seeing. Overall, our results indicate we should redefine visual aphantasia to distinguish individuals with faint or unseen visual images from those completely lacking a pictorial representation.

neuroscience↗

bioRxiv2024

Mental Rotation is a weak measure of the propensity to visualise.

There is increasing evidence of substantial differences in peoples capacity to voluntarily visualise - with some (Congenital Aphants) asserting they cannot visualise at all. Its been suggested that Congenital Aphants might be mistaken about their inability, as some have performed similarly on tasks purported to measure imagery - including the mental rotation task, where people decide if objects depicted from different viewpoints are the same or different. We examined how the vividness of peoples imagery is related to performance on a mental rotation task. People also reported on their response strategies. Mental rotation was an overall superior response strategy relative to non-visualising. However, the vividness of peoples imagery was only weakly associated with viewpoint contingent changes in task performance, and it did not predict changes in reliance on mental rotation as a response strategy. Overall, our data suggest performance on mental rotation tasks is a weak measure of peoples propensity to visualise.

neuroscience↗

bioRxiv2024

Imagery priming of binocular rivalry is not a reliable metric of individual differences in the subjective vividness of visualisations.

Most people can imagine images that they experience within their minds eye. However, there are marked individual differences, with some people reporting that they are unable to construct mental images at all (aphantasics), and others who report having imagined experiences that are as realistic as seeing (hyper-phantasics). The vividness of imagined images is most often measured via subjective self-report. Chang and Pearson (2018), however, have suggested that a binocular rivalry (BR) protocol can be used as an objective measure. They found that pre-imagining a moving input could enhance performance on an objective probe detection task when probes were embedded in imagery consistent inputs, as opposed to imagery inconsistent inputs. To date, nobody has assessed if this type of objective imagery priming can be used to predict the vividness of different peoples visualisations. Here, we report that imagery priming of objective sensitivity to probes within static BR inputs does not correlate with the typical ratings people use to describe the vividness of their visualisations (a between participants effect). However, objective priming of sensitivity to probes embedded in BR inputs was greater on trials when participants reported that their pre-imagined experience had been relatively vivid (a within participants effect). Overall, our data suggest that while imagery can prime objective sensitivity to probes during BR, there is currently no strong evidence that this effect can be used as an objective method of predicting the subjective vividness of different peoples visualisations. Highlights[tpltrtarr] There are marked individual differences in the subjective intensity of visual imagery [tpltrtarr]Most measures of the subjective intensity of visual imagery are subjective [tpltrtarr]A binocular rivalry probe-detection protocol has been suggested as an objective measure [tpltrtarr]The authors find that there is only a very small predictive relationship between outcomes in a binocular rivalry task and participants reported imagery strength [tpltrtarr]We still lack an objective measure that reliably predicts the subjective intensity of visual imagery

animal behavior and cognition↗

bioRxiv2023

Predicting the subjective intensity of imagined sensory experiences from electrophysiological measures of oscillatory brain activity.

Most people can conjure images and sounds that they experience in their minds. There are, however, marked individual differences. Some people report that they cannot generate imagined sensory experiences at all (aphantasics) and others report that they have unusually intense imagined experiences (hyper-phantasics). These individual differences have been linked to activity in sensory brain regions, driven by feedback. We would therefore expect imagined experiences to be associated with specific frequencies of oscillatory brain activity, as these can be a hallmark of neural interactions within and across regions of the brain. Replicating a number of other studies, relative to meditation we find that the act of engaging in imagining auditory or visual sensations is linked to reductions in the power of oscillatory brain activity across a broad range of frequencies, with prominent peaks in the alpha band (8-12 Hz). This oscillatory activity, however, did not predict individual differences in the subjective intensity of imagined experiences. For imagined audio experiences, these were rather predicted by reductions within the theta (6 - 9 Hz) and gamma (33 - 38 Hz) bands, and by increases in beta (15 - 17Hz) band activity. For imagined visual experiences these were predicted by reductions in lower (14 - 16Hz) and upper (29 - 32 Hz) beta band activity, and by an increase in mid-beta band (24 - 26 Hz) activity. Our data suggest that there is sufficient ground truth to the subjective reports that people use to describe the intensity of their imagined sensory experiences such that these can be predicted by the power of distinct rhythms of brain activity.

neuroscience↗

bioRxiv2023

A robust measure of metacognitive sensitivity and confidence criteria

Humans experience feelings of confidence in their decisions. In perception, these feelings are typically accurate - we tend to feel more confident about correct decisions. The degree of insight people have into the accuracy of their decisions is known as metacognitive sensitivity. Currently popular methods of estimating metacognitive sensitivity are subject to interpretive ambiguities because they assume that humans experience normally-shaped distributions of different experiences when they are repeatedly exposed to a single input. If, however, people have skewed distributions of experiences, or distributions with excess kurtosis (i.e. a distribution containing greater numbers of extreme experiences than is predicted by a normal distribution), calculations can erroneously underestimate metacognitive sensitivity. Here, we describe a means of estimating metacognitive sensitivity that is more robust against violations of the normality assumption. This improved method relies on estimating the precision with which people transition between making categorical decisions with relatively low to high confidence, and on comparing this with the precision with which they transition between making different types of perceptual category decision. The new method can easily be added to standard behavioral experiments. We provide free Matlab code to help researchers implement these analyses and procedures in their own experiments. Public Significance StatementSignal-detection theory is one of the most popular frameworks for analysing data from experiments of human behaviour - including investigations of confidence. The authors demonstrate that if a key assumption of this framework is inadvertently violated, analyses of confidence can lead to unwarranted conclusions. They develop a new and more robust measure of confidence.

neuroscience↗

bioRxiv2023

Extrastriate activity reflects the absence of local retinal input

The physiological blind spot corresponds to the optic disc where the retina contains no light-detecting photoreceptor cells. Our perception seemingly fills in this gap in input. Here we suggest that rather than an active process, such perceptual filling-in could instead be a consequence of the integration of visual inputs at higher stages of processing discounting the local absence of retinal input. Using functional brain imaging, we resolved the retinotopic representation of the physiological blind spot in early human visual cortex and measured responses while participants perceived filling-in. Responses in early visual areas simply reflected the absence of visual input. In contrast, higher extrastriate regions responded more to stimuli in the eye containing the blind spot than the fellow eye. However, this signature was independent of filling-in. We argue that these findings agree with philosophical accounts that posit that the concept of filling-in of absent retinal input is unnecessary.

neuroscience↗

bioRxiv2022

On why we lack confidence in signal-detection-based analyses of confidence

Signal-detection theory (SDT) is one of the most popular frameworks for analyzing data from studies of human behavior - including investigations of confidence. SDT-based analyses of confidence deliver both standard estimates of sensitivity (d), and a second estimate based only on high-confidence decisions - meta d. The extent to which meta d estimates fall short of d estimates is regarded as a measure of metacognitive inefficiency, quantifying the contamination of confidence by additional noise. These analyses rely on a key but questionable assumption - that repeated exposures to an input will evoke a normally-shaped distribution of perceptual experiences (the normality assumption). Here we show, via analyses inspired by an experiment and modelling, that when distributions of experiences do not conform with the normality assumption, meta d can be systematically underestimated relative to d. Our data therefore highlight that SDT-based analyses of confidence do not provide a ground truth measure of human metacognitive inefficiency. Public Significance StatementSignal-detection theory is one of the most popular frameworks for analysing data from experiments of human behaviour - including investigations of confidence. The authors show that the results of these analyses cannot be regarded as ground truth. If a key assumption of the framework is inadvertently violated, analyses can encourage conceptually flawed conclusions.

neuroscience↗

bioRxiv2020

An absence of temporal filling-in at the physiological blind-spot.

Visual objects that extend across physiological blind spots seem to encapsulate the extent of blindness, due to a process commonly referred to as a perceptual filling-in of spatial vision. It is unclear if temporal perception is similar, so we examined temporal relationships governing causality perception across the blind spot. We found the human brain does not allow for the time an object should take to traverse the blind-spot when engaging in a causal interaction. We also used electroencephalogram (EEG), to examine temporal signatures of elements flickering on and off in tandem, or in counter-phase. At a control site, we found more brain activity was entrained at the duty cycle by flicker relative to counter-phase changes, whereas these conditions were indistinguishable about blind spots. Our data suggest a common pool of neurons might encode temporal properties on either side of physiological blind-spots. This would explain the absence of any allowance for the extent of blindness in causality perception, and the weakened differences between temporal representations of flicker and counter-phased changes about the blind spot. Overall, our data suggest that, unlike spatial vision, there is no temporal filling-in for perceptual representations about physiological blind spots.

physiology↗

bioRxiv2020

Are alpha-band oscillations a default dynamic of the human visual brain, or a product of ongoing visual processes?

One of the seminal findings of cognitive neuroscience is that the power of alpha-band ([~]10 Hz) brain waves, in occipital regions, increases when people close their eyes. This has encouraged the view that alpha oscillations are a default dynamic, to which the visual brain returns in the absence of input. Accordingly, we might be unable to increase the power of alpha oscillations when the eyes are closed, above the level that would usually ensue. Here we report counter evidence. We used electroencephalography (EEG) to record brain activity when people had their eyes open and closed, before and after they had adapted to radial motion. The increase in the power of alpha oscillations when people closed their eyes was enhanced by adaptation to a broad range of radial motion speeds. This effect was greatest for 10Hz motion, but robust for other frequencies, and specifically for 7.5Hz. This last observation is important, as it rules against an ongoing entrainment of activity, at the adaptation frequency, as an explanation for our results. Instead, our data show that visual processes remain active when people close their eyes, and these can be modulated by adaptation to increase the power of alpha oscillations in occipital brain regions.

neuroscience↗

bioRxiv2020

Visual predictions, neural oscillations and Newtonian physics.

Prediction is considered a core function of the human visual brain, but relating this suggestion to real life is problematic, as findings regarding the neural correlates of prediction rely on abstracted experiments, not reminiscent of a typical visual diet. We addressed this by having people view videos of basketball, and asking them to predict jump shot outcomes while we recorded eye movements and brain activity. We used the brains understanding of physics to manipulate predictive success, by inverting footage. People had enhanced alpha-band activity in occipital brain regions when watching upright videos, and this predicted both an increase in predictive success and enhanced ball tracking. Alpha-band activity in visual brain regions has been linked to inhibition, so we regard our results as evidence that inhibition of task irrelevant information is a core function of predictive processes in the visual brain, enacted as people complete visual tasks typical of daily life.

neuroscience↗

bioRxiv2018

Comparing the aftereffects of motion and causality across visual co-ordinates

Albert Michotte (1946/1963) introduced causality into the realm of experimental phenomenology. He disputed Humes (1739/1978) claim that the impression of causality comes only from conscious inference. Since then, causality adaptation studies have suggested that the visual perception of causality undergoes sensory adaptation, akin to the retinally-specific aftereffects of motion or orientation adaptation. Here we present 5 Experiments that, together, dispute a view of retinotopically-mapped neural populations dedicated to causality detection. We first point to key issues in previous studies of causality adaptation. Then we extend the basic causality adaptation paradigm to show that causality aftereffects occur in spatially global visual space. We directly compare causality aftereffects to the motion aftereffect to show important differences in their co-ordinate mapping. Our data point to a role for cognitive inferences as being an important aspect of causality aftereffects, despite causal impressions being tightly constrained by sensory perception.

neuroscience↗

bioRxiv2018

The implied motion aftereffect changes decisions, but not confidence

Viewing static images depicting movement can result in a motion aftereffect: people tend to categorise direction signals as moving in the opposite direction to the implied motion of still photographs. This finding could indicate that inferred motion direction can penetrate sensory processing and impact perception. Equally possible, however, is that inferred motion impacts decision processes, but not perception. Here we test these two possibilities. Since both categorical decisions and subjective confidence are informed by sensory information, confidence can be informative about whether an aftereffect likely results from changes to perceptual or decision processes. We therefore leveraged subjective confidence as an additional measure of the implied motion aftereffect. In Experiment 1 (implied motion), we find support for decision-level changes only, with no change in subjective confidence. In Experiment 2 (real motion), we find equal changes to decisions and confidence. Our results suggest the implied motion aftereffect produces a bias in decision-making, but leaves perceptual processing unchanged.

neuroscience↗