Catherine Manning

The development of speed discrimination abilities

The processing of speed is a critical part of a childs visual development, allowing children to track and interact with moving objects. Despite such importance, no study has investigated the developmental trajectory of speed discrimination abilities or precisely when these abilities become adult-like. Here, we measured speed discrimination thresholds in 5-, 7-, 9-, 11-year-olds and adults using random dot stimuli with two different reference speeds (slow: 1.5 deg/s; fast: 6 deg/s). Sensitivity for both reference speeds improved exponentially with age and, at all ages, participants were more sensitive to the faster reference speed. However, sensitivity to slow speeds followed a more protracted developmental trajectory than that for faster speeds. Furthermore, sensitivity to the faster reference speed reached adult-like levels by 11 years, whereas sensitivity to the slower reference speed was not yet adult-like by this age. Different developmental trajectories may reflect distinct systems for processing fast and slow speeds. The reasonably late development of speed processing abilities may be due to inherent limits in the integration of neuronal responses in motion-sensitive areas in early childhood.

Processing Slow and Fast Motion in Children With Autism Spectrum Conditions

Consistent with the dorsal stream hypothesis, difficulties processing dynamic information have previously been reported in individuals with autism spectrum conditions (ASC). However, no research has systematically compared motion processing abilities for slow and fast speeds. Here, we measured speed discrimination thresholds and motion coherence thresholds in slow (1.5 deg/sec) and fast (6 deg/sec) speed conditions in children with an ASC aged 7 to 14 years, and age‐ and ability‐matched typically developing children. Unexpectedly, children with ASC were as sensitive as typically developing children to differences in speed at both slow and fast reference speeds. Yet, elevated motion coherence thresholds were found in children with ASC, but in the slow stimulus speed condition only. Rather than having pervasive difficulties in motion processing, as predicted by the dorsal stream hypothesis, these results suggest that children with ASC have a selective difficulty in extracting coherent motion information specifically at slow speeds. Understanding the effects of stimulus parameters such as stimulus speed will be important for resolving discrepancies between previous studies examining motion coherence thresholds in ASC and also for refining theoretical models of altered autistic perception. Autism Res 2013, 6: 531–541.

Averaging, not internal noise, limits the development of coherent motion processing

Highlights • Motion processing abilities develop gradually through childhood.• This lengthy development could be due to local noise and/or poor averaging.• 5–11-year-olds and adults performed equivalent noise and motion coherence tasks.• Through childhood, internal noise reduces and averaging increases.• Yet, only improved averaging explains developments in motion coherence sensitivity.

Children on the autism spectrum update their behaviour in response to a volatile environment

Abstract Typical adults can track reward probabilities across trials to estimate the volatility of the environment and use this information to modify their learning rate (Behrens et al., 2007). In a stable environment, it is advantageous to take account of outcomes over many trials, whereas in a volatile environment, recent experience should be more strongly weighted than distant experience. Recent predictive coding accounts of autism propose that autistic individuals will demonstrate atypical updating of their behaviour in response to the statistics of the reward environment. To rigorously test this hypothesis, we administered a developmentally appropriate version of Behrens et al.s (2007) task to 34 cognitively able children on the autism spectrum aged between 6 and 14 years, 32 age‐ and ability‐matched typically developing children and 19 typical adults. Participants were required to choose between a green and a blue pirate chest, each associated with a randomly determined reward value between 0 and 100 points, with a combined total of 100 points. On each trial, the reward was given for one stimulus only. In the stable condition, the ratio of the blue or green response being rewarded was fixed at 75:25. In the volatile condition, the ratio alternated between 80:20 and 20:80 every 20 trials. We estimated the learning rate for each participant by fitting a delta rule model and compared this rate across conditions and groups. All groups increased their learning rate in the volatile condition compared to the stable condition. Unexpectedly, there was no effect of group and no interaction between group and condition. Thus, autistic children used information about the statistics of the reward environment to guide their decisions to a similar extent as typically developing children and adults. These results help constrain predictive coding accounts of autism by demonstrating that autism is not characterized by uniform differences in the weighting of prediction error.

The effects of grouping on speed discrimination thresholds in adults, typically developing children, and children with autism.

Adult observers show elevated speed discrimination thresholds when comparing the speeds of objects moving across a boundary compared to those moving parallel to a boundary (Verghese & McKee, 2006)-an effect that has been attributed to grouping processes in conjunction with a prior for smooth motion. Here, we extended Verghese and McKees (2006) paradigm to typically developing children (n = 35) and children with autism (n = 26) and compared their performance with that of typical adults (n = 19). Speed discrimination thresholds were measured in three conditions: (a) with dots moving parallel to a boundary, (b) with dots moving perpendicular to a boundary, and (c) with dots in each stimulus half moving in orthogonal, oblique directions. As expected, participants had higher speed discrimination thresholds when dots appeared to cross a boundary compared to when dots moved parallel to the boundary. However, participants had even higher thresholds when dots moved in oblique, orthogonal directions, where grouping should be minimal. All groups of participants showed a similar pattern of performance across conditions although children had higher thresholds than adult participants overall. We consider various explanations for the pattern of performance obtained, including enhanced sensitivity for shearing motions and reduced sensitivity for discriminating different directions. Our results demonstrate that the speed discrimination judgments of typically developing children and children with autism are similarly affected by spatial configuration as those of typical adults and provide further evidence that speed discrimination is unimpaired in children with autism.

Brief Report: Coherent Motion Processing in Autism: Is Dot Lifetime an Important Parameter?.

Contrasting reports of reduced and intact sensitivity to coherent motion in autistic individuals may be attributable to stimulus parameters. Here, we investigated whether dot lifetime contributes to elevated thresholds in children with autism. We presented a standard motion coherence task to 31 children with autism and 31 typical children, with both limited and unlimited lifetime conditions. Overall, children had higher thresholds in the limited lifetime condition than in the unlimited lifetime condition. However, children with autism were affected by this manipulation to the same extent as typical children and were equally sensitive to coherent motion. Our results suggest that dot lifetime is not a critical stimulus parameter and speak against pervasive difficulties in coherent motion perception in children with autism.

Ensemble perception of emotions in autistic and typical children and adolescents

Ensemble perception, the ability to assess automatically the summary of large amounts of information presented in visual scenes, is available early in typical development. This ability might be compromised in autistic children, who are thought to present limitations in maintaining summary statistics representations for the recent history of sensory input. Here we examined ensemble perception of facial emotional expressions in 35 autistic children, 30 age- and ability-matched typical children and 25 typical adults. Participants received three tasks: a) an ‘ensemble’ emotion discrimination task; b) a baseline (single-face) emotion discrimination task; and c) a facial expression identification task. Children performed worse than adults on all three tasks. Unexpectedly, autistic and typical children were, on average, indistinguishable in their precision and accuracy on all three tasks. Computational modelling suggested that, on average, autistic and typical children used ensemble-encoding strategies to a similar extent; but ensemble perception was related to non-verbal reasoning abilities in autistic but not in typical children. Eye-movement data also showed no group differences in the way children attended to the stimuli. Our combined findings suggest that the abilities of autistic and typical children for ensemble perception of emotions are comparable on average.

Visual integration of direction and orientation information in autistic children

Background and aims The vision of autistic people has been characterised as focused on detail, with a disinclination (or reduced ability) to integrate information into coherent ‘wholes’. In contrast to this view, we recently demonstrated enhanced integration of visual motion signals in autistic children compared to typically developing children. Here, we aimed to investigate the robustness of our finding of increased motion integration in autism with a new sample of children and to determine whether increased integration in autistic children would extend to a static, orientation judgement. Methods We presented motion and orientation equivalent noise and coherence tasks to 46 autistic children aged 6 to 14 years and 45 typically developing children matched in age and non-verbal IQ. The equivalent noise tasks consisted of two interleaved conditions: a high-noise condition in which children judged the average direction or orientation of elements whose range of direction or orientations was manipulated, and a no-noise condition in which children judged the direction or orientation of elements sharing the same direction or orientation. Equivalent noise modelling provided estimates of internal noise (the precision with which children can estimate the orientation/direction of one element) and global sampling (how many elements children are effectively using to judge the overall orientation/direction). Children also completed coherence tasks in which the proportion of signal elements sharing the same direction or orientation amidst otherwise random noise elements was manipulated. We assessed group differences using a combination of frequentist and Bayesian statistical approaches. Results Analysis of the data in this new sample alone did not provide sufficient evidence either in favour or against the hypothesis of increased integration in autism. However, when combining motion data from this and the original experiment, autistic children exhibited superior integration of direction information in the high-noise condition compared to typically developing children, with similar no-noise and coherence thresholds. Equivalent noise modelling of these data revealed increased sampling in autistic children for motion information but no conclusive evidence for atypical levels of internal noise. There was no evidence of differences between autistic and typically developing children in the orientation equivalent noise and coherence tasks. Conclusions Overall, autistic children effectively integrated more direction information than typically developing children. However, the groups overlapped considerably and there was substantial individual variability, so that the effect may be difficult to detect in small groups. There was no indication of atypical integration of orientation in the current study, although larger samples will be required in order to provide conclusive evidence. Implications These results help characterise the nature of sensory processing in autism, which is of high import and relevance given the recent inclusion of sensory symptoms in diagnostic criteria. Increased integration of motion information could potentially lead to feelings of sensory overload in autistic children. If such increased integration is specific to motion information, domain-specific accounts of autistic perception will be required.

Reprint of “Investigating ensemble perception of emotions in autistic and typical children and adolescents”

Ensemble perception, the ability to assess automatically the summary of large amounts of information presented in visual scenes, is available early in typical development. This ability might be compromised in autistic children, who are thought to present limitations in maintaining summary statistics representations for the recent history of sensory input. Here we examined ensemble perception of facial emotional expressions in 35 autistic children, 30 age- and ability-matched typical children and 25 typical adults. Participants received three tasks: a) an ‘ensemble’ emotion discrimination task; b) a baseline (single-face) emotion discrimination task; and c) a facial expression identification task. Children performed worse than adults on all three tasks. Unexpectedly, autistic and typical children were, on average, indistinguishable in their precision and accuracy on all three tasks. Computational modelling suggested that, on average, autistic and typical children used ensemble-encoding strategies to a similar extent; but ensemble perception was related to non-verbal reasoning abilities in autistic but not in typical children. Eye-movement data also showed no group differences in the way children attended to the stimuli. Our combined findings suggest that the abilities of autistic and typical children for ensemble perception of emotions are comparable on average.

Visual Motion Prediction and Verbal False Memory Performance in Autistic Children: Prediction and false memory in autism

Recent theoretical accounts propose that atypical predictive processing can explain the diverse cognitive and behavioral features associated with autism, and that difficulties in making predictions may be related to reduced contextual processing. In this pre‐registered study, 30 autistic children aged 6–14 years and 30 typically developing children matched in age and non‐verbal IQ completed visual extrapolation and false memory tasks to assess predictive abilities and contextual processing, respectively. In the visual extrapolation tasks, children were asked to predict when an occluded car would reach the end of a road and when an occluded set of lights would fill up a grid. Autistic children made predictions that were just as precise as those made by typically developing children, across a range of occlusion durations. In the false memory task, autistic and typically developing children did not differ significantly in their discrimination between items presented in a list and semantically related, non‐presented items, although the data were insensitive, suggesting the need for larger samples. Our findings help to refine theoretical accounts by challenging the notion that autism is caused by pervasively disordered prediction abilities. Further studies will be required to assess the relationship between predictive processing and context use in autism, and to establish the conditions under which predictive processing may be impaired. Autism Res 2018, 11: 509–518.