Heida Maria Sigurdardottir

Visual processing difficulties have been reported in dyslexia, yet it remains unclear whether dyslexic and typical readers differ in how the visual system rapidly and automatically discriminates between stimuli. In this preregistered study, 31 matched pairs of adult dyslexic and typical readers completed three fast periodic visual stimulation paradigms while we recorded steady-state visual evoked potentials with EEG. Streams of objects, faces, and print were presented at 6 Hz, with every fifth image involving an identity change at 1.2 Hz. Against our predictions, responses to such changes were not lower for the dyslexic group in any paradigm. For objects, dyslexic readers instead showed higher responses to within-category changes despite similar behavioral accuracy, suggesting that greater neural resources were recruited for the same task. Across all three categories, dyslexic readers also showed elevated responses to the rapid image stream, pointing to a general difference in visual encoding. Neural responses to face identity changes predicted recognition accuracy in typical but not dyslexic readers, consistent with the two groups relying on different mechanisms to support behavior. These findings suggest that even in cases where visual discrimination ability is largely intact in adult dyslexic readers, the neural processes that support it and its link to behavior differ from those of typical readers.

Visual imagery varies widely across individuals, from aphantasia (no imagery) to hyperphantasia (highly vivid imagery), yet most measurement tools rely on verbal self-report with limited external anchoring. We introduce the Visual Imagery Visually Anchored Scale (VIVAS), which asks participants to reconstruct their mental images of objects from six categories (animals, buildings, faces, food, manmade objects, and novel objects) along three perceptual dimensions (opacity, sharpness, and color saturation) using visually presented anchors. VIVAS was administered to a probability-based panel randomly selected from the National Registry of Iceland; 205 completed the study and were included in analyses. VIVAS dimensions were highly related but not interchangeable: individual differences in color imagery reliably dissociated from those of opacity and sharpness, which suggests that visual imagery partly separates into its structural clarity and chromaticity. Imagery also differed systematically across categories. Novel objects elicited the weakest imagery on all three dimensions, which highlights a central role for familiarity in shaping imagery strength. In contrast, food items showed selectively enhanced color imagery, consistent with the functional importance of color for evaluating edibility and with the overlap between food- and color-selective regions in visual cortex. The structural clarity of imagery showed minimal category specificity beyond familiarity effects. VIVAS total scores did not differ by gender, age, education, or device type, consistent with robustness for online administration. Participants’ evaluations of VIVAS were generally favorable. VIVAS correlated moderately with the Vividness of Visual Imagery Questionnaire (VVIQ), well below the ceiling set by each instrument's reliability, and individual-level dissociations were striking: some participants scoring in the bottom 10% on one measure fell in the top quartile on the other. Verbal and visually anchored measures therefore appear to capture complementary, and sometimes divergent, facets of imagery, with implications for how aphantasia and hyperphantasia are defined and identified. Together, these findings position VIVAS as a reliable, visually grounded complement to existing verbal questionnaires. VIVAS captures both overall imagery strength as well as meaningful dimension- and category-specific structure that standard self-report tools cannot easily assess.

Reading is a fundamental everyday skill, yet not everyone easily acquires it. For decades, research focused on the role of phonological processing in reading difficulties while the visual component of reading was left behind. The high-level visual dysfunction hypothesis suggests that reading problems experienced by some individuals can indicate a broader impairment in visual cognition. In this preregistered study, we investigated whether object discrimination abilities, measured with a visual foraging task, predict concurrent reading performance in early readers. Participants included 1st and 3rd graders (approximate ages 6 and 8 years, respectively, total N = 163) assessed using standardized reading performance tests, phonological processing measures, rapid automatized naming of colors, a scale of ADHD-related symptoms, and a foraging paradigm involving object discrimination.In the foraging task, children selected matching objects from a display containing a central target exemplar, nine matching targets, and nine distractors. Trials varied by condition: basic-level (targets and distractors from different categories), subordinate-level (from the same category), and control (black and white circles). Object discrimination was operationalized as the number of targets participants correctly identified per second. Lower- and higher-level visual similarity of objects was assessed via activation patterns of the CORnet-S neural network. Semantic similarities of the stimuli were obtained through separate human ratings.The findings indicate that object discrimination significantly predicts reading performance, even after controlling for age, phonological processing, behaviors related to inattention, hyperactivity, and impulsivity, rapid automatized naming, and foraging speed during control trials. Additionally, we found that better reading skills are associated with more effective use of semantic and higher-level visual information during object discrimination. In contrast, lower-level visual information did not show a similar pattern.These results support the high-level visual dysfunction hypothesis of dyslexia and highlight the importance of visual object processing in reading — a factor that has for a long time been largely ignored in studies on reading difficulties.

Developmental prosopagnosia (DP) is a neurodevelopmental disorder characterized by profound difficulties with face recognition. While there are no commonly agreed criteria for classifying individuals with DP, most researchers utilize self-report measures as an essential part. Here, we report the outcome from two teams who independently examined and tried to improve the most widely used tool in the field: the 20-item Prosopagnosia Index (PI20). The two teams arrived at a 13-item solution (PI13) and a 5-item solution (PI5), respectively. Joining forces, we tested both abbreviated versions and the original PI20 in a prospective investigation, with the aim of validating and comparing the tools. We found that PI5 and PI13 provide valid and reliable assessment of face recognition problems, and we recommend PI5 as a screening tool for face recognition problems with potential for use in clinical settings, while PI13 may be better suited for research on individual differences in face recognition.

What information do people use for object perception, and how does this change across development? In this large-scale study (total n = 333), we investigated the development of object processing in a large sample of children (ages 4: n = 69; 6: n = 90; 8: n = 104) and a comparison group of adults (n = 70). Participants completed a fun and engaging object foraging task, requiring discrimination of target objects from distractors. We used human ratings as well as activation patterns from a neural network to quantify the visual and semantic information available for object discrimination. In line with our preregistered hypotheses (https://osf.io/84wxp), older children relied more on semantic and high-level visual information than younger children. Also as predicted, they tuned into the visual cues most diagnostic for the task—shape for basic-level distinctions (e.g., brush vs. pipe) and features for subordinate-level distinctions (e.g., two different bowties). Critically, an exploratory representational similarity analysis (RSA) nonetheless revealed remarkably similar underlying object representations across all age groups, suggesting that developmental changes in object perception are primarily quantitative rather than qualitative. These findings suggest that children's improved object discrimination abilities reflect increased access to relevant visual and semantic information. Overall, our results support a model of continuous development of high-level vision across the lifespan.

Visual mental imagery, or the ability to “see” with the mind’s eye, varies substantially across individuals. This vividness ranges from aphantasia, where no mental images are experienced, to hyperphantasia, characterized by exceptionally vivid imagery. In the present study we investigated the possible connection between the vividness of visual mental imagery and precision of information retrieval from visual memory. We hypothesized that individuals with weak or no imagery would show reduced memory precision compared to those with vivid imagery. Participants completed three tasks: a visual perception task (control), a visual working memory task, and a visual long-term memory task. Imagery vividness was assessed using the Vividness of Visual Imagery Questionnaire (VVIQ). In all tasks, participants adjusted the color of a grayscale test object to match a colored sample object shown previously (memory tasks) or simultaneously (perception task). Contrary to our hypothesis, there was no association between mental imagery vividness and memory precision. We discuss possible explanations, including the surprisingly widespread and apparently effective use of verbal strategies in visual memory tasks regardless of imagery strength.

What are the diagnostic dimensions on which objects differ visually? We constructed a two-dimensional object space based on such attributes captured by a deep convolutional neural network. These attributes can be approximated as stubby/spiky and animate-/inanimate-looking. If object space contributes to human visual cognition, this should have a measurable effect on object discrimination abilities. We administered an object foraging task to a large, diverse sample (N = 511). We focused on the stubby animate-looking "face quadrant" of object space given known variations in face discrimination abilities. Stimuli were picked out of tens of thousands of images to either match or not match with the coordinates of faces in object space. Results show that individual differences in face perception can to a large part be explained by variability in general object perception abilities (o-factor). However, additional variability in face processing can be attributed to visual similarity with faces as captured by dimensions of object space; people who struggle with telling apart faces also have difficulties with discriminating other objects with the same object space attributes. This study is consistent with a contribution of object space to human visual cognition. (PsycInfo Database Record (c) 2024 APA, all rights reserved).