Gestalt, Navon and Kanizsa illusion processing in CVI, ADHD, and dyslexia Children with Normal verbal IQ

Abstract

Introduction: Global Visual Selective Attention (VSA) is the ability to integrate multiple visual elements of a scene to achieve visual overview. This is essential for navigating crowded environments and recognizing objects or faces. Clinical pediatric research on global VSA deficits primarily focuses on autism spectrum disorder (ASD). However, in children with cerebral visual impairment (CVI) and other neurodevelopmental disorders (ADHD, dyslexia) similar deficits are reported. The aim of this study was to investigate global VSA performance in children with CVI, ADHD, dyslexia and neurotypical children by combing gaze-based measures with conventional neuropsychological tasks.

Methods: We included children aged 6-12 years with CVI (n = 20), ADHD (n = 30), dyslexia (n = 34) and neurotypical development (n = 37), all with normal verbal IQ. Eye tracking measurements were stepwise introduced within three global VSA tasks: Gestalt Closure (no eye tracking), Navon stimuli (eye tracking-based qualitative analysis) and Kanizsa Illusory Contours (KIC; eye tracking-based quantitative analysis). Verbal responses were compared with non-verbal gaze behavior.

Results: Children with CVI had significantly lower success rates on Gestalt Closure recognition, prolonged verbal response times on Navon stimuli, and decreased verbal and gaze performance on the KIC task compared to all other groups, irrespective of visual acuity. Children with ADHD and dyslexia performed similar to neurotypical children on all tasks.

Discussion: The results suggest а distinct global VSA deficit in children with CVI, which aligns with clinical observations of symptoms in daily life. Incorporating gaze-based analyses provided new information about search strategies beyond verbal answers and made the KIC task more inclusive for children with language and motor disabilities. Assessing global VSA within clinical CVI assessments could improve the differential diagnostic evaluations among children with CVI, ADHD and dyslexia, leading to more personalized treatment approaches.

Keywords: Gestalt closure; Kanizsa illusory contours; Navon; attention deficit hyperactivity disorder (ADHD); cerebral visual impairment (CVI); dyslexia; global visual selective attention.

Figure 1

(A) Kaufman Gestalt Closure task. (B) Navon task: congruent global/local elements (top) and incongruent global/local elements (bottom). (C) Kanizsa Illusory Contours: with an illusory contour (top) and without an illusory contour (down).

Figure 2

(A) Experimental design of the Navon Number Task. For the global and local set, it is explained in practice trials (A1) what level they must report, followed by three test trials (A2). (B) Area of interest (AOI) around the Navon stimulus, depicted in yellow. (C) Example of gaze behavior in one set of participating twins (12 years of age), one with CVI and one with neurotypical development.

Figure 3

(A) Experimental design of the Kanizsa Illusory Contour task. The fixation smiley appears for 1.5 s (A1). The displays consist of black (A3, A4) or black-and-white (A2) Pac-Man stimuli with (A2, A4) or without (A3) an illusory square target. (B) Area of interest (AOI) around the Navon stimulus. (C) Example of gaze behavior in one set of participating twins (12 years of age), one with CVI and one with neurotypical development.

Figure 4

Performance on the Gestalt Closures task, in mean scaled scores with error bars indicating ±1 Standard Error (SE). The light gray bar between the scaled score of 8 and 12 refers to the normal, or average, range. ***p < 0.001, **p < 0.010, *p < 0.05.

Figure 5

Group differences in mean Verbal Response Times (A) and Time to First Fixation (B) on the Navon Number Task per set, with error bars indicating ±1 Standard Error (SE). ***p < 0.001, **p < 0.010, *p < 0.05.

Figure 6

Group proportions of mean correct verbal answers (naming the illusory square) after the Kanizsa Illusory Contour Task, with error bars indicating ±1 Standard Error (SE). ***p < 0.001, **p < 0.010, *p < 0.05.

Figure 7

Group differences in gaze behavior on the Kanizsa Illusory Contour Task. Bars represent the mean Target Accuracy (A), Time to First Fixation (B), Target Fixation Duration (C), and Visual Search Area (D), with error bars indicating ±1 Standard Error (SE). ***p < 0.001, **p < 0.010, *p < 0.05.

Figure 8

Within-group differences between black and black and white Pac-Mans (A–D) and between target and no target conditions (E). Bars represent the mean Target Accuracy (A), Time to First Fixation (B), Target Fixation Duration (C), and Visual Search Area (D,E), with error bars indicating ±1 Standard Error (SE). ***p < 0.001, **p < 0.010, *p < 0.05.