Spatiotemporal deficits and their relationship to poor reading

Almagren, Bader 2026. Spatiotemporal deficits and their relationship to poor reading. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The purpose of this project was to determine whether poor temporal precision compromises spatial precision and reading performance by disrupting the sampling of visual information across time via fixational eye movement (FEMs). Although temporal processing deficits are well documented in developmental dyslexia, their perceptual consequences for spatial stability remain poorly investigated. Psychophysical experiments were undertaken to quantify temporal precision, spatial precision, and reading performance under different visual conditions. Temporal precision was measured using a temporal order judgement task, while spatial precision was assessed using spatial bisection tasks designed to manipulate the availability and reliability of retinal reference information. In an initial group-based study, adults with dyslexia exhibited markedly elevated temporal thresholds and poorer reading performance. Spatial precision was comparable to typical readers when a continuous retinal reference was available but deteriorated disproportionately when simultaneous reference information was removed. These findings indicate that temporal deficits do not produce a general spatial impairment but selectively disrupt spatial judgements when spatial information must be integrated across time. Subsequent experiments adopted an individual differences approach across a single mixed sample to dissociate retinal and extraretinal contributions to spatial stability and to quantify fixational eye movements. Spatial precision varied systematically with visual context, being greatest when retinal reference was stable, reduced when reference was absent. Temporal precision was associated with spatial thresholds primarily when stable retinal reference information was present. The interaction between temporal precision and FEMs was explicitly quantified as the product of temporal order thresholds and FEMs amplitude (TOT × FEMs amplitude). This measure captures the amount of retinal image motion occurring within the temporal sampling window. This combined measure predicted both spatial precision and reading performance, indicating that increased retinal image motion within longer temporal windows leads to greater positional uncertainty and reduced reading efficiency. Eye movement analyses revealed that FEMs predicted spatial precision in reference-based conditions, indicating that spatial judgements depend on positional alignment at the time of judgement. These findings demonstrate that temporal processing deficits impair visual performance indirectly and in a context-dependent manner, by degrading spatial stability under conditions requiring precise spatiotemporal alignment. This thesis provides a general link between temporal precision, visual stability, and reading performance, and shows that temporal deficits become functionally limiting only under specific visual constraints rather than reflecting a global spatial impairment

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Optometry and Vision Sciences
Subjects:	Q Science > Q Science (General)
Uncontrolled Keywords:	Temporal, Spatial, Dyslexia, Eye movements, Reading, Perception
Date of First Compliant Deposit:	24 August 2026
Last Modified:	24 Aug 2026 12:57
URI:	https://orca.cardiff.ac.uk/id/eprint/189118

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