Temporal order judgment in dyslexia

Evidence for visual temporal order processing below the threshold for conscious perception

Correctly discriminating the order of events arising in our environment is a fundamental temporal process that allows us to better understand and interact with our dynamic world. However, if consecutive events are separated by an interval of less than 20-40 ms, we cannot consciously perceive their relative order. Nevertheless, indirect evidence suggests that the sequential order of events separated by less than 20 ms might still be processed subconsciously. In our study, we aimed to provide evidence that temporal order processing can occur below the threshold for conscious perception. We developed a novel paradigm in which participants were instructed that a visual cue, composed of two coloured stimuli appearing in a particular order, would allow them to predict the shape of a subsequent target. The interval between the two stimuli allowed temporal order to be consciously perceived (66 ms interval) or not (17 ms interval), as verified by performance on a separate temporal order judgment task. Performance was compared to a control condition that provided no predictive information. In both experiments, reaction times were faster in the order-cue conditions compared to the control condition, whether the SOA separating events was longer (66 ms) or shorter (17 ms) than the typical temporal order threshold. Therefore, even when participants could not consciously perceive the temporal order of two consecutive stimuli, the relative sequence of events was nevertheless processed and used to optimise performance. These results suggest that temporal order can be processed subconsciously.

Unisensory and multisensory temporal processing in autism and dyslexia: A systematic review and meta-analysis

This study presents a comprehensive systematic review and meta-analysis of temporal processing in autism spectrum disorder (ASD) and developmental dyslexia (DD), two neurodevelopmental disorders in which temporal processing deficits have been highly researched. The results provide strong evidence for impairments in temporal processing in both ASD (g = 0.48) and DD (g = 0.82), as measured by judgments of temporal order and simultaneity. In individual analyses, multisensory temporal processing was impaired for both ASD and DD, and unisensory auditory, visual and tactile processing were all impaired in DD. In ASD, speech stimuli showed moderate impairment effect sizes, whereas nonspeech stimuli showed small effects. Greater reading and spelling skills in DD were associated with greater temporal precision. Temporal deficits did not show changes with age in either disorder. In addition to more clearly defining temporal impairments in ASD and DD, the results highlight common and distinct patterns of temporal processing between these disorders. Deficits are discussed in relation to existing theoretical models, and recommendations are made for future research.

Advantage of detecting visual events in the right hemifield is affected by reading skill

Visual perception is often not homogenous across the visual field and can vary depending on situational demands. The reasons behind this inhomogeneity are not clear. Here we show that directing attention that is consistent with a western reading habit from left to right, results in a ~32% higher sensitivity to detect transient visual events in the right hemifield. This right visual field advantage was largely reduced in individuals with reading difficulties from developmental dyslexia. Similarly, visual detection became more symmetric in skilled readers, when attention was guided opposite to the reading pattern. Taken together, these findings highlight a higher sensitivity in the right visual field for detecting the onset of sudden visual events that is well accounted for by left hemisphere dominated reading habit.

The effect of landscape photograph type on aesthetic judgments, attention, and memory in children with dyslexia

Given the link between visual stimuli and memory, children with dyslexia could benefit from research discovering what visual stimuli they find more pleasing and memorable. People like natural landscapes (e.g.,forests) more than human-made (e.g.,cityscapes) or "combined" landscapes (i.e.,combination of human-made and natural components, e.g.,tires in a meadow). The purpose was to determine if the greater likability for natural generalized to children with dyslexia and age-equivalent controls and if photograph type impacted recognition rates after the short and long term. All children liked natural landscape photographs the most but paid longer attention to combined landscape photographs. Both groups recognized all photograph types at a high rate after the short retention interval, but after the long interval, the children with dyslexia had better memory, especially for combined photographs. On the basis of these results, we advise educators to incorporate images of natural landscapes into the learning context in order to create a more aesthetically pleasing environment or to infuse combined images for a more engaging and memorable environment.

Crossmodal synesthetic congruency improves visual timing in dyslexic children

Consistent with the temporal ventriloquism effect, synesthetic correspondence between the features of visual size and auditory pitch has been shown to modulate the performance of visual temporal order judgment (TOJ) in typical adults. Here in the two main experiments we recruited seventeen dyslexic children and twenty typically developing children to perform a visual TOJ task and measured their ability of synesthetic correspondence between visual size and auditory pitch. In Experiment 1, participants were shown two consecutively presented visual discs that were temporally flanked by two synesthetic congruent or incongruent auditory beeps. In Experiment 2, participants received a crossmodal matching test (visual-size vs. auditory pitch). The results showed that compared to the typically developing group, dyslexic children benefited more from cross-modal synesthetic correspondence to partially compensate for their deficiency in visual TOJ task. The multisensory facilitation for timing performance was correlated with reading ability (Exp.1). Moreover, dyslexic children formed intact "congruent" matching of visually larger shapes to lower auditory pitch, and visually smaller shapes to higher auditory pitch, as did their typically developing peers (Exp 2). The results of our present study suggested general deficits of temporal processing in dyslexic children, However, with relatively intact ability of auditory pitch-visual size matching, dyslexic children could separate visual events using auditory cues. The current study also indicates a feasible way to improve the reading ability by exploiting temporal ventriloquism effect, modulated by appropriate crossmodal synesthetic associations.

Time perception and temporal order memory

The purpose of this research was to investigate the relation between the attentional resources underlying time perception and temporal order memory. Subjects made judgments about temporal attributes associated with a series of wordlists. Each word was displayed for 1.4s, and the lists contained 10 words (14s total), 15 words (21s total), or 20 words (28s total). Subjects judged either the list duration, the temporal order of the words, or both duration and temporal order. In addition, there were three mental workload conditions: control (no additional task requirements), and two mental arithmetic tasks (subtract 3 or subtract 7 from a series of random numbers). The results showed a pattern of bidirectional interference between timing and temporal order: the concurrent temporal order task interfered with duration judgments, and the concurrent timing task interfered with temporal order judgments. Bidirectional interference also occurred between the mental workload task and both duration judgments and temporal order judgments. The results indicate that duration and temporal order are closely related temporal attributes, and suggest that the processing of these attributes relies on a common set of executive attentional resources.

Temporal sampling in vision and the implications for dyslexia

It has recently been suggested that dyslexia may manifest as a deficit in the neural synchrony underlying language-based codes (Goswami, 2011), such that the phonological deficits apparent in dyslexia occur as a consequence of poor synchronisation of oscillatory brain signals to the sounds of language. There is compelling evidence to support this suggestion, and it provides an intriguing new development in understanding the aetiology of dyslexia. It is undeniable that dyslexia is associated with poor phonological coding, however, reading is also a visual task, and dyslexia has also been associated with poor visual coding, particularly visuo-spatial sensitivity. It has been hypothesized for some time that specific frequency oscillations underlie visual perception. Although little research has been done looking specifically at dyslexia and cortical frequency oscillations, it is possible to draw on converging evidence from visual tasks to speculate that similar deficits could occur in temporal frequency oscillations in the visual domain in dyslexia. Thus, here the plausibility of a visual correlate of the Temporal Sampling Framework is considered, leading to specific hypotheses and predictions for future research. A common underlying neural mechanism in dyslexia, may subsume qualitatively different manifestations of reading difficulty, which is consistent with the heterogeneity of the disorder, and may open the door for a new generation of exciting research.

Attention and the speed of information processing: posterior entry for unattended stimuli instead of prior entry for attended stimuli

Why are nearly simultaneous stimuli frequently perceived in reversed order? The origin of errors in temporal judgments is a question older than experimental psychology itself. One of the earliest suspects is attention. According to the concept of prior entry, attention accelerates attended stimuli; thus they have "prior entry" to perceptive processing stages, including consciousness. Although latency advantages for attended stimuli have been revealed in psychophysical studies many times, these measures (e.g. temporal order judgments, simultaneity judgments) cannot test the prior-entry hypothesis completely. Since they assess latency differences between an attended and an unattended stimulus, they cannot distinguish between faster processing of attended stimuli and slower processing of unattended stimuli. Therefore, we present a novel paradigm providing separate estimates for processing advantages respectively disadvantages of attended and unattended stimuli. We found that deceleration of unattended stimuli contributes more strongly to the prior-entry illusion than acceleration of attended stimuli. Thus, in the temporal domain, attention fulfills its selective function primarily by deceleration of unattended stimuli. That means it is actually posterior entry, not prior entry which accounts for the largest part of the effect.

Sound can improve visual search in developmental dyslexia

We examined whether developmental dyslexic adults suffer from sluggish attentional shifting (SAS; Hari and Renvall in Trends Cogn Sci 5:525-532, 2001) by measuring their shifting of attention in a visual search task with dynamic cluttered displays (Van der Burg et al. in J Exp Psychol Human 34:1053-1065, 2008). Dyslexics were generally slower than normal readers in searching a horizontal or vertical target among oblique distracters. However, the addition of a click sound presented in synchrony with a color change of the target drastically improved their performance up to the level of the normal readers. These results are in line with the idea that developmental dyslexics have specific problems in disengaging attention from the current fixation, and that the phasic alerting by a sound can compensate for this deficit.

Sound can improve visual search in developmental dyslexia

We examined whether developmental dyslexic adults suffer from sluggish attentional shifting (SAS; Hari and Renvall in Trends Cogn Sci 5:525-532, 2001) by measuring their shifting of attention in a visual search task with dynamic cluttered displays (Van der Burg et al. in J Exp Psychol Human 34:1053-1065, 2008). Dyslexics were generally slower than normal readers in searching a horizontal or vertical target among oblique distracters. However, the addition of a click sound presented in synchrony with a color change of the target drastically improved their performance up to the level of the normal readers. These results are in line with the idea that developmental dyslexics have specific problems in disengaging attention from the current fixation, and that the phasic alerting by a sound can compensate for this deficit.