Specific conditions for a selective deficit in memory for order in children with dyslexia

ABSTRACT

Short-term memory (STM) models distinguish between item and order memorization. The present study aims to explore how item and order STM are affected by the nature of the stimuli, the sequential versus simultaneous mode of presentation, the visual versus auditory presentation modality, the possibility of verbal recoding. A total of 20 children with dyslexia were matched one-by-one with 20 typically reading children on sex, age (8–14 years), and grade. Computerized STM tasks were administered while manipulating type (item vs. order), stimuli (letters vs. colors), sequentiality, input and output modality, as well as the presence/absence of articulatory suppression and distractors. General Linear Model analyses were conducted on accuracy scores for item and order STM. Both item and order recall scores were lower for children with dyslexia. Although order STM in the visual input condition turned out to be more impaired than item STM in the dyslexic group, both item and order memory impairments become evident when verbal recoding is prevented through articulatory suppression. Moreover, dyslexic children, unlike typical readers, were not facilitated by the linguistic nature of the stimuli to be remembered. The present findings suggest that the often-reported selective impairment of serial memory in dyslexia is restricted to stimuli that are verbal in nature or can be verbally recoded, whereas both item and order memory impairments become evident when verbal recoding is prevented through articulatory suppression. The presence of distractors is particularly detrimental to STM in the dyslexic group. The sensitivity to distractors, suppression, and stimuli in STM is predictive of reading performance.

KEYWORDS:

• Order short-term memory
• item short-term memory
• computerized assessment
• verbal recoding
• developmental dyslexia

Acknowledgments

The authors wish to thank Roberto Bombacigno, information system technician from the Laboratorio di Psicologia Sociale Applicata della Facoltà di Psicologia, Università Cattolica del Sacro Cuore di Milano (The Catholic University of the Sacred Heart in Milan) for programming the software used in this study. They also thank Alessio Toraldo for support in statistical analyses, two anonymous reviewers for their thoughtful comments, and the school staff, the parents, and the children who participated in the study.

Supplementary Material

Supplemental data for this article can be accessed at https://doi.org/10.1080/09297049.2018.1530746.

Notes

¹ The Italian names of the colors, the standard color names and their corresponding hex value: Rosa = Pink, #FFC0CB; Blu = Blue, #0000FF; Nero = Black, #000000; Viola = Dark Orchid, #9932CC; Verde = Green, #008000; Grigio = Dark Gray,#A9A9A9; Arancio = OrangeRed, #FF4500; Giallo = Yellow, #FFFF00; Marrone = SaddleBrown, #8B4513; Sabbia = Wheat, #F5DEB3; Fucsia = Fuchsia, #FF00FF; Azzurro = Powder Blue, #B0E0E6; Oro = Gold #FFD700; Bianco = White, #FFFFFF; Rosso = Red, #FF0000 (http://www.w3schools.com/html/html_colornames.asp).

² The same pattern of results has been found in a larger, less accurately selected sample of 81 participants- 50 TD and 31 with Dyslexia (from which the sample included in this study had been drawn), not excluding comorbidity with ADHD and other learning disorders: a Type x AS x Group interaction F(1,77) = 22.271, p < .001, partial η² = .224) emerged, explained by the lack of a Group x Type interaction F(1,77) = 0.017, p < .897, partial η² < .001) in the presence of AS and a significant Group x Type interaction (F(1,77) = 30.241, p < .001, partial η² = .282) when AS was not requested. This rules out the hypothesis that the results of the study depend on having analyzed a small sample.