The visual attention span (VAS) deficit hypothesis in developmental dyslexia posits that a subset of dyslexic individuals shows a multielement parallel processing deficit due to reduced visual attention capacity. However, the attention-based interpretation of poor performance on VAS tasks is hotly debated. The purpose of the present paper is to clarify this issue through a critical review of relevant behavioural and neurobiological findings. We first examine the plausibility of alternative verbal interpretations of VAS performance, evaluating whether performance on VAS tasks might reflect verbal short-term memory, verbal coding or visual-to-verbal mapping skills. We then focus on the visual dimensions of VAS tasks to question whether VAS primarily reflects visuo-attentional rather than more basic visual skills. Scrutiny of the available behavioural and neurobiological findings not only points to a deficit of visual attention in dyslexic individuals with impaired VAS but further suggests a selective endogenous attentional system deficit that relates to atypical functioning of the brain dorsal attentional network. The overview clarifies the debate on what is being measured through VAS tasks and provides insights on how to interpret the VAS deficit in developmental dyslexia.

中文翻译：

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发育性阅读障碍中的视觉注意力跨度缺陷：基于视觉注意力缺陷的证据回顾

发育性阅读障碍中的视觉注意力跨度 (VAS) 缺陷假说认为，由于视觉注意力能力下降，一部分阅读障碍个体表现出多元素并行处理缺陷。然而，基于注意力的对 VAS 任务表现不佳的解释引起了激烈的争论。本文的目的是通过对相关行为和神经生物学发现的批判性审查来澄清这个问题。我们首先检查 VAS 表现的替代口头解释的合理性，评估 VAS 任务的表现是否可能反映口头短期记忆、口头编码或视觉到口头映射技能。然后，我们关注 VAS 任务的视觉维度，以质疑 VAS 是否主要反映视觉注意力而不是更基本的视觉技能。对现有行为和神经生物学研究结果的审查不仅指出了 VAS 受损的阅读障碍个体的视觉注意力不足，而且进一步表明与大脑背侧注意力网络的非典型功能有关的选择性内源性注意力系统缺陷。该概述阐明了关于通过 VAS 任务测量什么的争论，并提供了有关如何解释发育性阅读障碍中的 VAS 缺陷的见解。