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When the illumination falling on a surface change, so does the reflected light. Despite this, adult observers are good at perceiving surfaces as relatively unchanging-an ability termed colour constancy. Very few studies have investigated colour constancy in infants, and even fewer in children. Here we asked whether there is a difference in colour constancy between children and adults; what the developmental trajectory is between six and 11 years; and whether the pattern of constancy across illuminations and reflectances differs between adults and children. To this end, we developed a novel, child-friendly computer-based object selection task. In this, observers saw a dragon's favourite sweet under a neutral illumination and picked the matching sweet from an array of eight seen under a different illumination (blue, yellow, red, or green). This set contained a reflectance match (colour constant; perfect performance) and a tristimulus match (colour inconstant). We ran two experiments, with two-dimensional scenes in one and three-dimensional renderings in the other. Twenty-six adults and 33 children took part in the first experiment; 26 adults and 40 children took part in the second. Children performed better than adults on this task, and their performance decreased with age in both experiments. We found differences across illuminations and sweets, but a similar pattern across both age groups. This unexpected finding might reflect a real decrease in colour constancy from childhood to adulthood, explained by developmental changes in the perceptual and cognitive mechanisms underpinning colour constancy, or differences in task strategies between children and adults. Highlights Six- to 11-year-old children demonstrated better performance than adults on a colour constancy object selection task. Performance decreased with age over childhood. These findings may indicate development of cognitive strategies used to overcome automatic colour constancy mechanisms.

Large walls and other typical boundaries strongly influence neural activity related to navigation and the representations of spatial layouts. They are also major aids to reliable navigation behavior in young children and non-human animals. Is this because they are physical boundaries (barriers to movement), or because they present certain visual features, such as visually extended 3D surfaces? Here, these two factors were dissociated by using immersive virtual reality and real boundaries. Eighty adults recalled target locations in one of four environments: plywood, where a virtual wall coincided with a large piece of real plywood; pass through, where the virtual wall coincided with empty space and participants could pass through it; pass over, where the virtual wall was projected downward to be visible underneath a transparent floor; and cones, where the walls were replaced with traffic cones. One condition had features that were boundaries and looked like boundaries (plywood); two had features that were not boundaries but looked like boundaries (pass over/through); and one had features that were not boundaries and did not look like boundaries (cones). The precision and bias of responses changed only as a function of looking like a boundary. This suggests that variations in spatial coding are more closely linked to the visual properties of environmental layouts than to whether they contain physical boundaries (barriers to movement).

Reliability-weighted averaging of multiple perceptual estimates (or cues) can improve precision. Research suggests that newly-learned statistical associations can be rapidly integrated in this way for efficient decision-making. Yet, it remains unclear if integration of newly-learned statistics into decision-making can directly influence perception, rather than taking place only at a decision stage. In two experiments, we implicitly taught observers novel associations between shape and colour. Observers made colour matches by adjusting the colour of an oval to match a simultaneously presented reference. As the colour of the oval changed across trials, so did its shape according to a novel mapping of axis ratio to colour. Observers showed signatures of reliability-weighted averaging – a precision-improvement in both experiments and reweighting of the newly-learned shape cue with changes in uncertainty in Experiment 2. To ask whether this was accompanied by perceptual effects, Experiment 1 tested for “forced fusion” by measuring colour discrimination thresholds with and without incongruent novel cues. Experiment 2 tested for a “memory colour effect”, observers adjusting the colour of ovals with different axis ratios until they appeared grey. There was no evidence for forced fusion and the opposite of a memory colour effect. Overall, our results suggest that the ability to quickly learn novel cues and integrate them with familiar cues is not immediately (within the short duration of our experiments, and in the domain of colour and shape) accompanied by common perceptual effects.

Cue combination describes the use of two sensory cues together to increase perceptual precision. Internal relative bias describes a situation in which two cues to the same state of the world are perceived as signaling different states of the world on average. Current theory and evidence have difficulty accounting for many instances where cue combination is absent, such as in children under 10 years old, and in a variety of tasks. Here we show that internal relative biases between cues could be a key explanatory factor. Experiment 1, studying children's three-dimensional (slant) perception via disparity and texture, found a negative cross-sectional correlation between internal relative bias and cue combination behavior in 7- to 10-year-olds. Strikingly, children who had below-median levels of internal relative bias were able to combine cues, unlike the typical result for that age range. Experiment 2, studying adults' visual-auditory localization, found that cue combination behavior increased after an intervention designed to decrease internal relative bias. We interpret this as strong but preliminary evidence that internal relative bias can disrupt cue combination behavior. This provides a plausible mechanism to explain why children under 10 generally do not combine cues and why the audiovisual cue combination is so inconsistent in adults. Moving forward, we suggest that researchers who fail to find an expected cue combination effect should further investigate the possibility of issues with internal relative bias. Decreasing internal relative bias may also be an important goal for rehabilitation and sensory substitution or augmentation approaches to promoting efficient multisensory perception.

Observers in perceptual tasks are often reported to combine multiple sensory cues in a weighted average that improves precision—in some studies, approaching statistically optimal (Bayesian) weighting, but in others departing from optimality, or not benefitting from combined cues at all. To correctly conclude which combination rules observers use, it is crucial to have accurate measures of their sensory precision and cue weighting. Here, we present a new approach for accurately recovering these parameters in perceptual tasks with continuous responses. Continuous responses have many advantages, but are susceptible to a central tendency bias, where responses are biased towards the central stimulus value. We show that such biases lead to inaccuracies in estimating both precision gains and cue weightings, two key measures used to assess sensory cue combination. We introduce a method that estimates sensory precision by regressing continuous responses on targets and dividing the variance of the residuals by the squared slope of the regression line, “correcting-out” the error introduced by the central bias and increasing statistical power. We also suggest a complementary analysis that recovers the sensory cue weights. Using both simulations and empirical data, we show that the proposed methods can accurately estimate sensory precision and cue weightings in the presence of central tendency biases. We conclude that central tendency biases should be (and can easily be) accounted for to consistently capture Bayesian cue combination in continuous response data.

After becoming disoriented, an organism must use the local environment to reorient and recover vectors to important locations. A new theory, adaptive combination, suggests that the information from different spatial cues is combined with Bayesian efficiency during reorientation. To test this further, we modified the standard reorientation paradigm to be more amenable to Bayesian cue combination analyses while still requiring reorientation in an allocentric (i.e., world-based, not egocentric) frame. Twelve adults and 20 children at ages 5 to 7 years old were asked to recall locations in a virtual environment after a disorientation. Results were not consistent with adaptive combination. Instead, they are consistent with the use of the most useful (nearest) single landmark in isolation. We term this adaptive selection. Experiment 2 suggests that adults also use the adaptive selection method when they are not disoriented but are still required to use a local allocentric frame. This suggests that the process of recalling a location in the allocentric frame is typically guided by the single most useful landmark rather than a Bayesian combination of landmarks. These results illustrate that there can be important limits to Bayesian theories of the cognition, particularly for complex tasks such as allocentric recall., Public Significance Statement Whether studying the development of children’s spatial cognition, creating artificial intelligence with human-like capacities, or designing civic spaces, we can benefit from a strong understanding of how humans process the space around them. Here we tested a prominent theory that brings together statistical theory and psychological theory (Bayesian models of perception and memory) but found that it could not satisfactorily explain our data. Our findings suggest that when tracking the spatial relations between objects from different viewpoints, rather than efficiently combining all the available landmarks, people often fall back to the much simpler method of tracking the spatial relation to the nearest landmark.

People can learn new sensory skills that augment their perception, such as human echolocation. However, it is not clear to what extent these can become an integral part of the perceptual repertoire. Can they show automatic use, integrated with the other senses, or do they remain cognitively-demanding, cumbersome, and separate? Here, participants learned to judge distance using an echo-like auditory cue. We show that use of this new skill met three key criteria for automaticity and sensory integration: (1) enhancing the speed of perceptual decisions; (2) processing through a non-verbal route and (3) integration with vision in an efficient, Bayes-like manner. We also show some limits following short training: integration was less-than-optimal, and there was no mandatory fusion of signals. These results demonstrate key ways in which new sensory skills can become automatic and integrated, and suggest that sensory augmentation systems may have benefits beyond current applications for sensory loss.

Previous studies suggest that to achieve color constancy, the human visual system makes use of multiple cues, including a priori assumptions about the illumination (“daylight priors”). Specular highlights have been proposed to aid constancy, but the evidence for their usefulness is mixed. Here, we used a novel cue-combination approach to test whether the presence of specular highlights or the validity of a daylight prior improves illumination chromaticity estimates, inferred from achromatic settings, to determine whether and under which conditions either cue contributes to color constancy. Observers made achromatic settings within three-dimensional rendered scenes containing matte or glossy shapes, illuminated by either daylight or nondaylight illuminations. We assessed both the variability of these settings and their accuracy, in terms of the standard color constancy index (CCI). When a spectrally uniform background was present, neither CCIs nor variability improved with specular highlights or daylight illuminants (Experiment 1). When a Mondrian background was introduced, CCIs decreased overall but were higher for scenes containing glossy, as opposed to matte, shapes (Experiments 2 and 3). There was no overall reduction in variability of settings and no benefit for scenes illuminated by daylights. Taken together, these results suggest that the human visual system indeed uses specular highlights to improve color constancy but only when other cues, such as from the local surround, are weakened.

The brain's ability to integrate information from the different senses is essential for decreasing sensory uncertainty and ultimately limiting errors. Temporal correspondence is one of the key processes that determines whether information from different senses will be integrated and is influenced by both experience- and task-dependent mechanisms in adults. Here we investigated the development of both task- and experience-dependent temporal mechanisms by testing 7-8-year-old children, 10-11-year-old children, and adults in two tasks (simultaneity judgment, temporal order judgment) using audiovisual stimuli with differing degrees of association based on prior experience (low for beep-flash vs. high for face-voice). By fitting an independent channels model to the data, we found that while the experience-dependent mechanism of audiovisual simultaneity perception is already adult-like in 10-11-year-old children, the task-dependent mechanism is still not. These results indicate that differing maturation rates of experience-dependent and task-dependent mechanisms underlie the development of multisensory integration. Understanding this development has important implications for clinical and educational interventions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Prior information represents the long-term statistical structure of an environment. For example, colds develop more often than throat cancer, making the former a more likely diagnosis for a sore throat. There is ample evidence for effective use of prior information during a variety of perceptual tasks, including the ability to recall locations using an egocentric (self-based) frame. However, it is not yet known if people can use prior information effectively when using an allocentric (world-based) frame. Forty-eight adults were shown sixty sets of three target locations in a sparse virtual environment with three beacons. The targets were drawn from one of four prior distributions. They were then asked to point to the targets after a delay and a change in perspective. While searches were biased towards the beacons, we did not find any evidence that participants successfully exploited the prior distributions of targets. These results suggest that allocentric reasoning does not conform to normative Bayesian models: we saw no evidence for use of priors in our cognitively-complex (allocentric) task, unlike in previous, simpler (egocentric) recall tasks. It is possible that this reflects the high biological cost of processing precise allocentric information.

Prior knowledge can help observers in various situations. Adults can simultaneously learn two location priors and integrate these with sensory information to locate hidden objects. Importantly, observers weight prior and sensory (likelihood) information differently depending on their respective reliabilities, in line with principles of Bayesian inference. Yet, there is limited evidence that observers actually perform Bayesian inference, rather than a heuristic, such as forming a look-up table. To distinguish these possibilities, we ask whether previously-learnt priors will be immediately integrated with a new, untrained likelihood. If observers use Bayesian principles, they should immediately put less weight on the new, less reliable, likelihood (“Bayesian transfer”). In an initial experiment, observers estimated the position of a hidden target, drawn from one of two distinct distributions, using sensory and prior information. The sensory cue consisted of dots drawn from a Gaussian distribution centred on the true location with either low, medium, or high variance; the latter introduced after block three of five to test for evidence of Bayesian transfer. Observers did not weight the cue (relative to the prior) significantly less in the high compared to medium variance condition, counter to Bayesian predictions. However, when explicitly informed of the different prior variabilities, observers placed less weight on the new high variance likelihood (“Bayesian transfer”), yet substantially diverged from ideal. Much of this divergence can be captured by a model that weights sensory information, according only to internal noise in using the cue. These results emphasise the limits of Bayesian models in complex tasks.

It is often unclear which course of action gives the best outcome. We can reduce this uncertainty by gathering more information, but gathering information always comes at a cost. For example, a sports player waiting too long to judge a ball's trajectory will run out of time to intercept it. Efficient samplers must therefore optimize a trade-off: when the costs of collecting further information exceed the expected benefits, they should stop sampling and start acting. In visually guided tasks, adults can make these trade-offs efficiently, correctly balancing any reductions in visuomotor uncertainty against cost factors associated with increased sampling. To investigate how this ability develops during childhood, we tested 6- to 11-year-olds, adolescents, and adults on a visual localization task in which the costs and benefits of sampling were formalized in a quantitative framework. This allowed us to compare participants to each other and to an ideal observer who maximizes expected reward. Visual sampling became substantially more efficient between 6 and 11 years, converging onto adult performance in adolescence. Younger children systematically undersampled information relative to the ideal observer and varied their sampling strategy more. Further analyses suggested that young children used a suboptimal decision rule that insufficiently accounted for the chance of task failure, in line with a late developing ability to compute with probabilities and costs. We therefore propose that late development of efficient information sampling, a crucial element of real-world decision-making under risk, may form an important component of suboptimality in child perception, action, and decision-making. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Central to the concept of the “cognitive map” is that it confers behavioral flexibility, allowing animals to take efficient detours, exploit shortcuts, and avoid alluring, but unhelpful, paths. The neural underpinnings of such naturalistic and flexible behavior remain unclear. In two neuroimaging experiments, we tested human participants on their ability to navigate to a set of goal locations in a virtual desert island riven by lava, which occasionally spread to block selected paths (necessitating detours) or receded to open new paths (affording real shortcuts or false shortcuts to be avoided). Detours activated a network of frontal regions compared with shortcuts. Activity in the right dorsolateral PFC specifically increased when participants encountered tempting false shortcuts that led along suboptimal paths that needed to be differentiated from real shortcuts. We also report modulation in event-related fields and theta power in these situations, providing insight to the temporal evolution of response to encountering detours and shortcuts. These results help inform current models as to how the brain supports navigation and planning in dynamic environments.

Successful navigation can require realizing the current path choice was a mistake and the best strategy is to retreat along the recent path: 'backtrack'. Despite the wealth of studies on the neural correlates of navigation little is known about backtracking. To explore the neural underpinnings of backtracking we tested humans during functional magnetic resonance imaging on their ability to navigate to a set of goal locations in a virtual desert island riven by lava which constrained the paths that could be taken. We found that on a subset of trials, participants spontaneously chose to backtrack and that the majority of these choices were optimal. During backtracking, activity increased in frontal regions and the dorsal anterior cingulate cortex, while activity was suppressed in regions associated with the core default-mode network. Using the same task, magnetoencephalography and a separate group of participants, we found that power in the alpha band was significantly decreased immediately prior to such backtracking events. These results highlight the importance for navigation of brain networks previously identified in processing internally-generated errors and that such error-detection responses may involve shifting the brain from default-mode states to aid successful spatial orientation. This work was supported by the Wellcome Trust (grant no. 094850/Z/10/Z) and James S. McDonnell Foundation to H.J.S., and the Gatsby Charitable Foundation (P.D.).

Humans are effective at dealing with noisy, probabilistic information in familiar settings. One hallmark of this is Bayesian Cue Combination: combining multiple noisy estimates to increase precision beyond the best single estimate, taking into account their reliabilities. Here we show that adults also combine a novel audio cue to distance, akin to human echolocation, with a visual cue. Following two hours of training, subjects were more precise given both cues together versus the best single cue. This persisted when we changed the novel cue’s auditory frequency. Reliability changes also led to a re-weighting of cues without feedback, showing that they learned something more flexible than a rote decision rule for specific stimuli. The main findings replicated with a vibrotactile cue. These results show that the mature sensory apparatus can learn to flexibly integrate new sensory skills. The findings are unexpected considering previous empirical results and current models of multisensory learning.

Prior knowledge can help observers in various situations. Adults can simultaneously learn two location priors and integrate these with sensory information to locate hidden objects. Importantly, observers weight prior and sensory (likelihood) information differently depending on their respective reliabilities, in line with principles of Bayesian inference. Yet, there is limited evidence that observers actually perform Bayesian inference, rather than a heuristic, such as forming a look-up table. To distinguish these possibilities, we ask whether previously learned priors will be immediately integrated with a new, untrained likelihood. If observers use Bayesian principles, they should immediately put less weight on the new, less reliable, likelihood ("Bayesian transfer"). In an initial experiment, observers estimated the position of a hidden target, drawn from one of two distinct distributions, using sensory and prior information. The sensory cue consisted of dots drawn from a Gaussian distribution centered on the true location with either low, medium, or high variance; the latter introduced after block three of five to test for evidence of Bayesian transfer. Observers did not weight the cue (relative to the prior) significantly less in the high compared to medium variance condition, counter to Bayesian predictions. However, when explicitly informed of the different prior variabilities, observers placed less weight on the new high variance likelihood ("Bayesian transfer"), yet, substantially diverged from ideal. Much of this divergence can be captured by a model that weights sensory information, according only to internal noise in using the cue. These results emphasize the limits of Bayesian models in complex tasks.

Improvements in visuospatial perception such as contrast sensitivity and Vernier acuity continue until late in childhood, but the neural mechanisms driving these age-related changes are currently unclear. One contributing factor could be the protracted development of spatial tuning of neuronal populations across the visual cortex. Here we tested this possibility using population receptive field (pRF) mapping (Dumoulin and Wandell, 2008) in 6-to 12-year-old children and adults. We fitted pRF models to BOLD signals measured in areas V1-V4 and V3a during fMRI whilst participants watched wedge and ring stimuli traversing the visual field. Cortical magnification and the width of pRF tuning functions changed with viewing eccentricity in all participants. However, there were no age-related changes in pRF size, shape, cortical magnification, or map consistency across any of the visual areas measured. These results suggest that visuospatial perception in late childhood beyond age 6 years is not substantially limited by low-level spatial tuning properties of neuronal populations in visual cortex. Instead, performance improvements in this period may reflect more efficient use of the spatial information available in the visual system when forming perceptual judgments. These findings are an important step towards disentangling which neural mechanisms contribute to the eventual emergence of mature spatial vision, and for understanding the processes that determine the scope for visual plasticity at different stages of life.

Central to the concept of the ‘cognitive map’ is that it confers behavioural flexibility, allowing animals to take efficient detours, exploit shortcuts and realise the need to back-track rather than persevere on a poorly chosen route. The neural underpinnings of such naturalistic and flexible behaviour remain unclear. During fMRI we tested human subjects on their ability to navigate to a set of goal locations in a virtual desert island riven by lava, which occasionally shifted to block selected paths (necessitating detours) or receded to open new paths (affording shortcuts). We found that during self-initiated back-tracking, activity increased in frontal regions and the dorsal anterior cingulate cortex, while activity in regions associated with the core default-mode network was suppressed. Detours activated a network of frontal regions compared to shortcuts. Activity in right dorsolateral prefrontal cortex specifically increased when participants encountered new plausible shortcuts but which in fact added to the path (false shortcuts). These results help inform current models as to how the brain supports navigation and planning in dynamic environments.Significance StatementAdaptation to change is important for survival. Although real-world spatial environments are prone to continual change, little is known about how the brain supports navigation in dynamic environments where flexible adjustments to route plans are needed. Here, we used fMRI to examine the brain activity elicited when humans took forced detours, identified shortcuts and spontaneously back-tracked along their recent path. Both externally and internally generated changes in the route activated the fronto-parietal attention network, whereas only internally generated changes generated increased activity in the dorsal anterior cingulate cortex with a concomitant disengagement in regions associated with the default-mode network. The results provide new insights into how the brain plans and re-plans in the face of a changing environment.

The capacity to take efficient detours and exploit novel shortcuts during navigation is thought to be supported by a cognitive map of the environment. Despite advances in understanding the neural basis of the cognitive map, little is known about the neural dynamics associated with detours and shortcuts. Here, we recorded magnetoencephalography from humans as they navigated a virtual desert island riven by shifting lava flows. The task probed their ability to take efficient detours and shortcuts to remembered goals. We report modulation in event-related fields and theta power as participants identified real shortcuts and differentiated these from false shortcuts that led along suboptimal paths. Additionally, we found that a decrease in alpha power preceded ‘back-tracking’ where participants spontaneously turned back along a previous path. These findings help advance our understanding of the fine-grained temporal dynamics of human brain activity during navigation and support the development of models of brain networks that support navigation.

We agree with Rahnev & Denison (R&D) that to understand perception at a process level, we must investigate why performance sometimes deviates from idealised decision models. Recent research reveals that such deviations from optimality are pervasive during perceptual development. We argue that a full understanding of perception requires a model of how perceptual systems become increasingly optimised during development.

Although children with autism spectrum disorder (ASD) show atypical sensory processing, evidence for impaired integration of multisensory information has been mixed. In this study, we took a Bayesian model-based approach to assess within-modality integration of congruent and incongruent texture and disparity cues to judge slant in typical and autistic adolescents. Human adults optimally combine multiple sources of sensory information to reduce perceptual variance but in typical development this ability to integrate cues does not develop until late childhood. While adults cannot help but integrate cues, even when they are incongruent, young children's ability to keep cues separate gives them an advantage in discriminating incongruent stimuli. Given that mature cue integration emerges in later childhood, we hypothesized that typical adolescents would show adult-like integration, combining both congruent and incongruent cues. For the ASD group there were three possible predictions (1) “no fusion”: no integration of congruent or incongruent cues, like 6-year-old typical children; (2) “mandatory fusion”: integration of congruent and incongruent cues, like typical adults; (3) “selective fusion”: cues are combined when congruent but not incongruent, consistent with predictions of Enhanced Perceptual Functioning (EPF) theory. As hypothesized, typical adolescents showed significant integration of both congruent and incongruent cues. The ASD group showed results consistent with “selective fusion,” integrating congruent but not incongruent cues. This allowed adolescents with ASD to make perceptual judgments which typical adolescents could not. In line with EPF, results suggest that perception in ASD may be more flexible and less governed by mandatory top-down feedback. Autism Res 2015. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research

Human adults can combine perceptual estimates from different senses to minimize uncertainty, by taking a reliability-weighted average (the maximum likelihood estimate, MLE). Although research has shown that healthy human adults reweight estimates as their reliability changes from one trial to the next, less is known about how humans adapt to gradual long-term changes in sensory reliability. This study assessed whether individuals diagnosed with progressive visual deterioration, due to retinal disease, combined auditory and visual cues to location according to optimal (MLE) predictions. Twelve patients with central visual loss, 10 patients with peripheral visual loss, and 12 normally sighted adults were asked to localize visual and/or auditory targets in central (1°-18°) and peripheral (36°-53°) locations. Normally sighted adults and patients with peripheral visual loss showed multisensory uncertainty reduction and cue weighting in line with MLE predictions. In contrast, patients with central visual loss did not weight estimates appropriately in either the center or the periphery, and failed to meet MLE predictions in the periphery. Our results show that one visual loss patient group succeeded at optimal cue combination, whereas the other patient group (patients with central vision loss) did not. We propose that sensory remapping due to changes in fixation behavior may contribute to apparent failures in the latter group. (PsycINFO Database Record

Purpose.: To validate a novel, automated test of infant resolution acuity based on remote eye-tracking.\ud \ud Methods.: Infants aged 2 to 12 months were tested binocularly using a new adaptive computerized test of infant vision using eye tracking (ACTIVE), and Keeler infant acuity cards (KIAC). The ACTIVE test ran automatically, using remote eye-tracking to assess whether the infant fixated a black-and-white grating of variable spatial frequency. Test-retest reliability was assessed by performing each test twice. Accuracy was assessed by comparing acuity measures across tests and with established age-norms, and by comparing low-contrast acuity estimates in adults with data reported previously.\ud \ud Results.: All infants completed the ACTIVE test at least once. Median test duration was 101 seconds. Measured visual acuity increased with age (P < 0.001), and 90% of mean acuity estimates were within previously published 90% tolerance limits (based on acuity-card age norms). Acuity estimates were also correlated, within-subjects, with results from the KIAC (P = 0.004). In terms of reliability, 86% of acuity estimates deviated by ≤1 octave, with no significant difference in test-retest reliability between the ACTIVE and KIAC procedures (P = 0.461). In adults, acuity estimates from the ACTIVE test did not differ significantly from values reported by previous authors (P > 0.183).\ud \ud Conclusions.: An adaptive computerized test of infant vision using eye-tracking provides a rapid, automated measure of resolution acuity in preverbal infants. The ACTIVE performed comparably to the current clinical gold standard (acuity cards) in terms of testability, reliability, and accuracy, and its principles can be extended to measure other visual functions.

Purpose To characterize retinal structure and function in achromatopsia (ACHM) in preparation for clinical trials of gene therapy. Design Cross-sectional study. Participants Forty subjects with ACHM. Methods All subjects underwent spectral domain optical coherence tomography (SD-OCT), microperimetry, and molecular genetic testing. Foveal structure on SD-OCT was graded into 5 distinct categories: (1) continuous inner segment ellipsoid (ISe), (2) ISe disruption, (3) ISe absence, (4) presence of a hyporeflective zone (HRZ), and (5) outer retinal atrophy including retinal pigment epithelial loss. Foveal and outer nuclear layer (ONL) thickness was measured and presence of hypoplasia determined. Main Outcome Measures Photoreceptor appearance on SD-OCT imaging, foveal and ONL thickness, presence of foveal hypoplasia, retinal sensitivity and fixation stability, and association of these parameters with age and genotype. Results Forty subjects with a mean age of 24.9 years (range, 6–52 years) were included. Disease-causing variants were found in CNGA3 (n = 18), CNGB3 (n = 15), GNAT2 (n = 4), and PDE6C (n = 1). No variants were found in 2 individuals. In all, 22.5% of subjects had a continuous ISe layer at the fovea, 27.5% had ISe disruption, 20% had an absent ISe layer, 22.5% had an HRZ, and 7.5% had outer retinal atrophy. No significant differences in age ( P = 0.77), mean retinal sensitivity ( P = 0.21), or fixation stability ( P = 0.34) across the 5 SD-OCT categories were evident. No correlation was found between age and foveal thickness ( P = 0.84) or between age and foveal ONL thickness ( P = 0.12). Conclusions The lack of a clear association of disruption of retinal structure or function in ACHM with age suggests that the window of opportunity for intervention by gene therapy is wider in some individuals than previously indicated. Therefore, the potential benefit for a given subject is likely to be better predicted by specific measurement of photoreceptor structure rather than simply by age. The ability to directly assess cone photoreceptor preservation with SD-OCT and/or adaptive optics imaging is likely to prove invaluable in selecting subjects for future trials and measuring the trials' impact.

Purpose: To assess the feasibility of macular integrity assessment (MAIA) microperimetry (MP) in children. Also to establish representative outcome measures (differential light sensitivity, fixation stability, test–retest reliability) for children without visual impairment.\ud \ud Methods: Thirty-three adults and 33 children (9–12 years) were asked to perform three monocular MAIA examinations within a single session (dominant eye only).\ud \ud Results: Children exhibited poorer test–retest reliability than adults for measures of both mean sensitivity (95% coefficient of repeatability [CoR95] = 2.7 vs. 2.3 dB, P = 0.036) and pointwise sensitivity (CoR95 = 6.2 vs. 5.7 dB, P < 0.001). Mean sensitivity was lower in children (27.6 vs. 29.5 dB, P < 0.001), and fixation stability was poorer (95% bivariate contour ellipse area [BCEA95] = 4.58 vs. 1.14, P < 0.001). Mean sensitivity was negatively correlated with fixation stability (r = −0.44, P < 0.001). Both children and adults exhibited substantial practice effects, with mean sensitivity improving by 0.5 dB (adults) and 0.9 dB (children) between examinations 1 and 2 (P ≤ 0.017). There were no significant differences between examinations 2 and 3 (P ≥ 0.374).\ud \ud Conclusions: Microperimetry is feasible in 9- to 12-year-old children. However, systematically lower sensitivities mean that the classification boundary for “healthy” performance should be lowered in children, pending development of techniques to improve attentiveness/fixation that may reduce or remove this difference. High measurement variability suggests that the results of multiple tests should be averaged when possible. Learning effects are a potential confound, and it is recommended that the results of the first examination be discarded.

We examined the development of visual cue integration in a desktop working-memory task using boxes with different visual action cues (opening actions) and perceptual surface cues (colours, monochromatic textures, or images of faces). Children had to recall which box held a hidden toy, based on (a) the action cue, (b) the surface cue, or (c) a conjunction of the two. Results from three experiments show a set of asymmetries in children's integration of action and surface cues. The 18-24-month-olds disregarded colour in conjunction judgements with action; 30-36-month-olds used colour but disregarded texture. Images of faces were not disregarded at either age. We suggest that 18-24-month-olds' disregard of colour, seen previously in reorientation tasks (Hermer and Spelke, 1994), may represent a general phenomenon, likened to uneven integration between the dorsal and ventral streams in early development.

Reorientation tasks, in which disoriented participants attempt to relocate objects using different visual cues, have previously been understood to depend on representing aspects of the global organisation of the space, for example its major axis for judgements based on geometry. Careful analysis of the visual information available for these tasks shows that successful performance could be based on the much simpler process of storing a visual 'snapshot' at the target location, and subsequently moving in order to match it. We tested 4-8-year olds on a new spatial reorientation task that could not be solved based on information directly contained in any retinal projection that they had been exposed to, but required participants to infer how the space is structured. Only 6-8-year olds showed flexible recall from novel viewpoints. Five-year olds were able to recall locations given movement information or a unique proximal landmark, but without these they could not do so, even when they were not disoriented or when the landmark was a familiar object. These results indicate that early developing spatial abilities based on view matching and self motion are supplemented by a later-developing process that takes into account the structure of spatial layouts and so enables flexible recall from arbitrary viewpoints.

PURPOSE: To report on two population screening programs designed to detect significant refractive errors in 8308 8- to 9-month-old infants, examine the sequelae of infant hyperopia, and test whether early partial spectacle correction improved visual outcome (strabismus and acuity). The second program also examined whether infant hyperopia was associated with developmental differences across various domains such as language, cognition, attention, and visuomotor competences up to age 7 years. Linked programs in six European countries assessed costs of infant refractive screening. METHOD: In the first program, screening included an orthoptic examination and isotropic photorefraction, with cycloplegia. In the second program we carried out the same screening procedure without cycloplegia. Hyperopic infants (> or = +4 D) were followed up alongside an emmetropic control group, with visual and developmental measures up to age 7 years, and entered a controlled trial of partial spectacle correction. RESULTS: The second program showed that accommodative lag during photorefraction with a target at 75 cm (focus > or = +1.5 D) was a marker for significant hyperopia. In each program, prevalence of significant hyperopia at 9 to 11 months was around 5%; manifest strabismus was 0.3% at 9 months and 1.5 to 2.0% by school age. Infant hyperopia was associated with increased strabismus and poor acuity at 4 years. Spectacle wear by infant hyperopes produced better visual outcome than in uncorrected infants, although an improvement in strabismus was found in the first program only. The corrections did not affect emmetropization to 3.5 years; however, both corrected and uncorrected groups remained more hyperopic than controls in the preschool years. The hyperopic group showed poorer overall performance than controls between 1 and 7 years on visuoperceptual, cognitive, motor, and attention tests, but showed no consistent differences in early language or phonological awareness. Relative cost estimates suggest that refractive screening programs can detect visual problems in infancy at lower overall cost than surveillance in primary care. CONCLUSIONS: Photo/videorefraction can successfully screen infants for refractive errors, with visual outcomes improved through early refractive correction. Infant hyperopia is associated with mild delays across many aspects of visuocognitive and visuomotor development. These studies raise the possibility that infant refractive screening can identify not only visual problems, but also potential developmental and learning difficulties.

The ability to use different sensory signals in conjunction confers numerous advantages on perception. Multisensory perception in adults is influenced by factors beyond low-level stimulus properties such as semantic congruency. Sensitivity to semantic relations has been shown to emerge early in development; however, less is known about whether implementation of these associations changes with development or whether development in the representations themselves might modulate their influence. Here, we used a Stroop-like paradigm that requires participants to identify an auditory stimulus while ignoring a visual stimulus. Prior research shows that in adults visual distractors have more impact on processing of auditory objects than vice versa; however, this pattern appears to be inverted early in development. We found that children from 8 years of age (and adults) gain a speed advantage from semantically congruent visual information and are disadvantaged by semantically incongruent visual information. At 6 years of age, children gain a speed advantage for semantically congruent visual information but are not disadvantaged by semantically incongruent visual information (as compared with semantically unrelated visual information). Both children and adults were influenced by associations between auditory and visual stimuli, which they had been exposed to on only 12 occasions during the learning phase of the study. Adults showed a significant speed advantage over children for well-established associations but showed no such advantage for newly acquired pairings. This suggests that the influence of semantic associations on multisensory processing does not change with age but rather these associations become more robust and, in turn, more influential.

Human adults can optimally integrate visual and non-visual self-motion cues when navigating, while children up to 8 years old cannot. Whether older children can is unknown, limiting our understanding of how our internal multisensory representation of space develops. Eighteen adults and fifteen 10- to 11-year-old children were guided along a two-legged path in darkness (self-motion only), in a virtual room (visual + self-motion), or were shown a pre-recorded walk in the virtual room while standing still (visual only). Participants then reproduced the path in darkness. We obtained a measure of the dispersion of the end-points (variable error) and of their distances from the correct end point (constant error). Only children reduced their variable error when recalling the path in the visual + self-motion condition, indicating combination of these cues. Adults showed a constant error for the combined condition intermediate to those for single cues, indicative of cue competition, which may explain the lack of near-optimal integration in this group. This suggests that later in childhood humans can gain from optimally integrating spatial cues even when in the same situation these are kept separate in adulthood.

While basic visual functions have been described in subjects with congenital achromatopsia (ACHM), little is known about their mid- or high-level cortical visual processing. We compared midlevel cortical visual processing in ACHM subjects (n = 11) and controls (n = 20).Abilities to detect global form, global motion, and biological motion embedded in noise were tested across a range of light levels, including scotopic, in which both ACHM subjects and controls must rely on rods. Contrast sensitivity functions (CSFs) were also measured.Achromatopsia subjects showed differential impairments across tests. In scotopic conditions, global form was most impaired, while biological motion was normal. In a subset of three ACHM subjects with normal scotopic CSFs, two of the three showed global form perception worse than controls; all showed global motion comparable to controls; and strikingly, two of the three showed biological motion perception superior to controls.The cone signal appears to play a crucial role in the development of perception of global form, as in ACHM this is impaired even in scotopic conditions, in which controls also have to rely on rods, and even in ACHM subjects with no scotopic spatial vision loss. In contrast, the rod signal appears sufficient for the development of normal (or even superior) extrastriate biological motion perception. These results suggest that ACHM leads to atypical development of cortical vision, highlighting the need to better understand the potential for further reorganization of cortical visual processing following new therapies aimed at restoring cone function.

Psychophysical studies have frequently found that adults with normal hearing exhibit systematic errors (biases) in their auditory localisation judgments. Here we tested (i) whether systematic localisation errors could reflect reliance on prior knowledge, as has been proposed for other systematic perceptual biases, and (ii) whether auditory localisation biases can be reduced following training with accurate visual feedback. Twenty-four normal hearing participants were asked to localise the position of a noise burst along the azimuth before, during, and after training with visual feedback. Consistent with reliance on prior knowledge to reduce sensory uncertainty, we found that auditory localisation biases increased when auditory localisation uncertainty increased. Specifically, participants mis-localised auditory stimuli as being more eccentric than they were, and did so more when auditory uncertainty was greater. However, biases also increased with eccentricity, despite no corresponding increase in uncertainty, which is not readily explained by use of a simple prior favouring peripheral locations. Localisation biases decreased (improved) following training with visual feedback, but the reliability of the visual feedback stimulus did not change the effects of training. We suggest that further research is needed to identify alternative mechanisms, besides use of prior knowledge, that could account for increased perceptual biases under sensory uncertainty.

Using landmarks and other scene features to recall locations from new viewpoints is a critical skill in spatial cognition. In an immersive virtual reality task, we asked children 3.5–4.5 years old to remember the location of a target using various cues. On some trials they could use information from their own self-motion. On some trials they could use a view match. In the very hardest kind of trial, they were ‘teleported’ to a new viewpoint and could only use an allocentric spatial representation. This approach provides a strict test for allocentric coding (without either a matching viewpoint or self-motion information) while avoiding additional task demands in previous studies (it does not require them to deal with a small table-top environment or to manage stronger cue conflicts). Both the younger and older groups were able to point back at the target location better than chance when they could use view matching and/or self-motion, but allocentric recall was only seen in the older group (4.0–4.5). In addition, we only obtained evidence for a specific kind of allocentric recall in the older group: they tracked one major axis of the space significantly above chance, r(158) = .28, but not the other, r(158) = −.01. We conclude that there is a major qualitative change in coding for spatial recall around the fourth birthday, potentially followed by further development towards fully flexible recall from new viewpoints.

SummaryCorrectly localising sensory stimuli in space is a formidable challenge for the newborn brain. A new study provides a first glimpse into how human brain mechanisms for sensory remapping develop in the first year of life.