Verbal and Spatial Working Memory Capacity in Blind Adults and the Possible Influence of Age at Blindness Onset: A Systematic Review and Meta-analysis

Abstract

The loss of a sense, such as vision, forces individuals to adapt to their environment and its demands in a variety of ways. In the case of blindness, significant neurofunctional and cognitive changes have been documented. However, there is no clear consensus on the differences in performance between adult blind participants and sighted controls in cognitive processes such as working memory (WM). Two variables are important, including the cognitive task used to measure working memory and the age at which vision loss occurs. This review is aimed at exploring potential disparities in verbal and spatial WM performance between blind and sighted adults, as well as understanding how these differences may be influenced by the age of vision loss. A systematic search across PsycArticles, PsycInfo, Medline, and Web of Science databases identified 21 pertinent studies. The studies were categorized, and effect sizes were calculated through meta-analysis, distinguishing between verbal (auditory simple forward and backward span, complex span, and n-back) and visuospatial WM tasks (adapted Corsi-block and simple storage tasks, imagery tasks, and complex storage tasks). Visual sensory loss induces adaptations affecting WM function in blind participants. In the verbal domain, improved phonological processing and/or serial item position encoding might facilitate WM retrieval. In contrast, in spatial WM, an over-reliance on serial processing may hinder strategic grouping in blind individuals. This review highlights the need to further explore the role of age at the time of vision loss. Although evidence suggests that adaptations to serial processing may be more pronounced in early development, particularly in comparison to those who become blind in adulthood, the available data are limited. The study calls for further research to deepen our understanding of cognitive adaptations and their temporal dynamics in response to vision loss.

Keywords: Congenitally blind; Early blind; Late blind; Vision impairment; Working memory.