Events often unfold over a time course that is amenable to prediction, as when a sprinter learns the constant foreperiod from set to go. This lets us temporally prepare. For many foreperiod distributions, the conditional probability of an event (e.g. a traffic light turning green) increases across time, so preparation should similarly increase, improving reaction times (RTs). Modelling has demonstrated such a quantitative match between mean RT across different foreperiods and the (inverted) subjective hazard function (or some related preparation function). However, modelling has provided few insights into how temporal preparation sculpts the tradeoff between RTs and anticipatory errors. Furthermore, the standard simplifying assumption that the subjective foreperiod distribution is stable offers no account of well-established history effects. To address these and several further issues, here we present a modelling architecture that incorporates an initial Stimulus Independent Process into a Non-Stationary Poisson account of simple Reaction Time (SIP-theN-SPuRT). SIP-theN-SPuRT derives a temporal preparation signal from an estimated foreperiod distribution that is updated from trial to trial. This signal, which may saturate at a physiological limit, feeds into three processes, reflecting urgency, modulation of drive from change detectors, and residual sensorimotor delays. We compared the predictions of nine SIP-theN-SPuRT model variants with new and existing simple-RT datasets. Best fits were obtained by the model in which each trial’s putative preparation signal gradually asymptotes (or saturates), after initially following a subjective hazard function.

Most people can imagine images that they experience within their mind^s 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 people^s 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 people^s visualisations. ### Competing Interest Statement The authors have declared no competing interest.

A minority of people (Aphantasics) report an inability to visualise. Aphantasia has been linked to Autism - a neurodevelopmental condition affecting social interactions. There is a risk of a circular logic informing proposed links, as the most popular metric of autistic traits, the Autism-Spectrum Quotient (AQ), has an Imagination subscale with items relating directly and indirectly to imagery. We tested for inter-relationships between imagery vividness ratings and the expression of autistic traits, using metrics that do and do not encompass an Imagination subscale. We also conducted hierarchical linear regression analyses to assess the contributions of different AQ subscale scores to imagery inter-relationships. Only in our highest-powered study (N = 308) were we able to detect a weak inter-relationship between AQ scores and imagery, independent of the Imagination subscale. We suggest that only a weak inter-relationship should exist, as many autistic people describe themselves as visual thinkers who have strong imagery.

In mental rotation (MR) tasks people can be asked to decide if pairs of objects depicted from different viewpoints are the same, or different. A common response strategy is to visualise one of the two objects rotating, until it is visualised from the same viewpoint as the other object. However, some people, Congenital Aphants, assert that they cannot visualise, and yet they perform similarly on MR tasks. This could mean that Congenital Aphants are mistaken about their inability to visualise. Alternatively, we reasoned that MR tasks might be an unreliable metric of people's propensity to rely on visualisation in MR tasks. In a sample of the general population, we had people report on their response strategies on a trial-by-trial basis. Neither people's overall propensity to visualise nor their propensity to visualise on different viewpoint trials was related to viewpoint-contingent changes in MR task performance. There was only a weak association between viewpoint-contingent changes in MR task performance and viewpoint-contingent changes in the proportion of visualising trials. Overall, our data suggest that MR task performance is a weak measure of people's propensity to visualise.

Oddball paradigms involve the presentation of sequences of repeated events that are broken by a novel "oddball." These have been used to examine the neural and perceptual consequences of predictive processes in the brain. Two intriguing perceptual findings are that people are more sensitive to visual content embedded in oddballs and that people perceive oddballs as longer lasting-relative to repeated events. Recent investigations have looked at the possibility that fluctuations in attention during presentation sequences might impact perception though. Because the number of repeated "standards" (that do not require a behavioral judgment) seen before a "test" (which can require a behavioral judgment) is often circumscribed, as more standards are encountered, the probability of a further standard decreases, whereas the probability of a test increases. So, later tests can be anticipated, whereas early tests are improbable. It has been shown that when all tests can be anticipated, and all tests are equally likely to be a further repeated standard or an oddball, oddballs still seem longer lasting than repeats. Here we show that the same conditions undermine the visual acuity advantage for oddball content. Our experiment clarifies that this increase in acuity for oddballs results from a degradation of acuity to repeat tests that cannot be anticipated. We found that people's pupils tended to dilate as they expected a test, consistent with top-down attention scaling with test probability. In a second experiment, we replicated the time perception difference and the lack of visual acuity difference under the same experimental conditions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Most people can imagine images that they experience within their mind's eye. However, there are marked individual differences, with some people reporting that they are unable to visualise (aphantasics), and others who report having imagined experiences that are as realistic as seeing (hyper-phantasics). The vividness of imagery 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 are 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 people's visualisations. Here, we report that imagery priming of objective sensitivity to probes within static BR inputs does not correlate with the 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 more vivid than average (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 a reliable objective method to predict the subjective vividness of different people's visualisations.

The authors are both self-described congenital aphantasics, who feel they have never been able to have volitional imagined visual experiences during their waking lives. In addition, Loren has atypical experiences of a number of visual phenomena that involve an extrapolation or integration of visual information across space. In this perspective, we describe Loren’s atypical experiences of a number of visual phenomena, and we suggest these ensue because her visual experiences are not strongly shaped by inhibitory feedback or by prior expectations. We describe Loren as having Deep Aphantasia, and Derek as shallow, as for both a paucity of feedback might prevent the generation of imagined visual experiences, but for Loren this additionally seems to disrupt activity at a sufficiently early locus to cause atypical experiences of actual visual inputs. Our purpose in describing these subjective experiences is to alert others to the possibility of there being sub-classes of congenital aphantasia, one of which—Deep Aphantasia, would be characterized by atypical experiences of actual visual inputs.

The oddball protocol has been used to study the neural and perceptual consequences of implicit predictions in the human brain. The protocol involves presenting a sequence of identical repeated events that are eventually broken by a novel “oddball” presentation. Oddball presentations have been linked to increased neural responding and to an exaggeration of perceived duration relative to repeated events. Because the number of repeated events in such protocols is circumscribed, as more repeats are encountered, the conditional probability of a further repeat decreases—whereas the conditional probability of an oddball increases. These facts have not been appreciated in many analyses of oddballs; repeats and oddballs have rather been treated as binary event categories. Here, we show that the human brain is sensitive to conditional event probabilities in an active, visual oddball paradigm. P300 responses (a relatively late component of visually evoked potentials measured with EEG) tended to be greater for less likely oddballs and repeats. By contrast, P1 responses (an earlier component) increased for repeats as a goal-relevant target presentation neared, but this effect occurred even when repeat probabilities were held constant, and oddball P1 responses were invariant. We also found that later, more likely oddballs seemed to last longer, and this effect was largely independent of the number of preceding repeats. These findings speak against a repetition suppression account of the temporal oddball effect. Overall, our data highlight an impact of event probability on later, rather than earlier, electroencephalographic measures previously related to predictive processes—and the importance of considering conditional probabilities in sequential presentation paradigms.

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 people have normally shaped distributions of different experiences when they are repeatedly exposed to a single input. If this normality assumption is violated, calculations can erroneously underestimate metacognitive sensitivity. Here, we describe a means of estimating metacognitive sensitivity that is more robust to violations of the normality assumption. This improved method can easily be added to standard behavioral experiments, and the authors provide Matlab code to help researchers implement these analyses and experimental procedures.

There are substantial differences in the capacity of people to have imagined visual experiences, ranging from a lifelong inability (Congenital Aphantasia) to people who report having imagined experiences that are as vivid as actually seeing (Hyper-Phantasia). While Congenital Aphantasia has typically been framed as a cognitive deficit, it is possible that a weak or absent ability to have imagined visual sensations is balanced by a heightened resistance to intrusive thoughts - which are experienced as an imagined sensation. Here, we report on a direct test of that proposition. We asked people to either imagine, or to try not to imagine having a range of audio and visual experiences while we recorded their brain activity with electroencephalography (EEG). Ratings describing the subjective vividness of different people's voluntary visualisations predicted if they would also report having involuntary visualisations - such as an imagined experience of seeing a pink elephant when they were asked not to. Both the prevalence of different people's involuntary visualisations and the typical vividness of their visualisations could be predicted by neural correlates of disinhibition, working memory, and neural feedback. Our data suggest that the propensity of people to have involuntary visual experiences can scale with the subjective intensity of their typical experiences of visualisation.

Neural responses to sensory inputs can scale with the likelihood of encountering the input. This is consistent with the predictive coding framework, in that the human brain is expected to be less responsive to predicted inputs. Typically, however, prediction is not explicitly measured. It is inferred from the probability of encountering an event. When an input is explicitly predicted, responses to predicted inputs can be enhanced. Here, we ask if this effect can be ascribed to a generic priming effect, from pre-cogitating about one of two possible inputs. Consistent with this, we find that P300s (a relatively late event-related potential measured with electroencephalography) are greater for explicitly predicted audio and visual inputs, and that this effect cannot be distinguished from a priming effect from pre-imagining audio or visual presentations. Evidence indicates that participants engaged in pre-imagining presentations, as we were able to decode online what type of presentation (audio or visual) they were imagining with a high success rate (approx. 73%), and we encouraged compliance with neuro-feedback regarding this success rate. Our data confirm that human cortex can be more responsive to inputs that have been subject to pre-cogitation-including explicit predictions. This highlights that while anticipatory processes can reduce responding to likely inputs, they can also enhance responding to explicitly predicted inputs.

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 a Resting-State we find that the act of engaging in auditory or in visual imagery 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 audio imagery, these were rather predicted by reductions within the theta (6–9 Hz) and gamma (33–38 Hz) bands, and by increases in beta (15–17 Hz) band activity. For visual imagery these were predicted by reductions in lower (14–16 Hz) 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 in the subjective reports people use to describe the intensity of their imagined sensory experiences to allow these to be linked to the power of distinct rhythms of brain activity. In future, we hope to combine this approach with better measures of the subjective intensity of imagined sensory experiences to provide a clearer picture of individual differences in the subjective intensity of imagined experiences, and of why these eventuate.

There is increasing evidence of substantial differences in the capacity of people to voluntarily visualise, with some (Congenital Aphants) asserting they cannot visualise at all. It has 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. ### Competing Interest Statement The authors have declared no competing interest.

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.