Objects in Space

In this thesis, we explore how objects affect the space around them. We show that spatial information is extracted from even completely novel objects. Information derived from the shape of objects is swiftly and automatically integrated into a variety of processes, such as the allocation of visual attention, the programming of eye movements, and the perception of motion. We provide evidence supporting that the lateral intraparietal area (LIP) of the macaque is able to extract such spatial information from objects. We also show that IPS1, the putative human homologue of LIP, can represent space not just in pure retinotopic coordinates but can code for space relative to the location of an object

The Role of Visual Factors in Dyslexia

What are the causes of dyslexia? Decades of research reflect a determined search for a single cause where a common assumption is that dyslexia is a consequence of problems with converting phonological information into lexical codes. But reading is a highly complex activity requiring many well-functioning mechanisms, and several different visual problems have been documented in dyslexic readers. We critically review evidence from various sources for the role of visual factors in dyslexia, from magnocellular dysfunction through accounts based on abnormal eye movements and attentional processing, to recent proposals that problems with high-level vision contribute to dyslexia. We believe that the role of visual problems in dyslexia has been underestimated in the literature, to the detriment of the understanding and treatment of the disorder. We propose that rather than focusing on a single core cause, the role of visual factors in dyslexia fits well with risk and resilience models that assume that several variables interact throughout prenatal and postnatal development to either promote or hinder efficient reading

Reading fluency and ADHD symptoms: Initial testing of IS-FORM, IS-PSEUDO, and SWAN in a sample of Icelandic children

The small-scale study presented here was the first test of three instruments in a sample of Icelandic children: IS-FORM, IS-PSEUDO, and the Strengths and Weaknesses of ADHD-symptoms and Normal-behavior (SWAN) rating scale. Participants in this study were children in the 4th grade of a school in Reykjavik (10 girls and 10 boys). Guardians completed SWAN to assess their children's behavior. The researchers measured children's reading fluency for real Icelandic word forms (IS-FORM) and pseudowords (IS-PSEUDO) onsite. Lesferill standardized reading fluency exam scores and both Icelandic language and mathematics scores from the 4th grade Icelandic National Exams (academic achievement) were collected from the Directorate of Education. IS-FORM and IS-PSEUDO showed all signs of being reliable and valid instruments for assessing the reading fluency of 4th grade children (Chronbach's alpha for the IS-FORM 1, IS-FORM 2, and IS-PSEUDO together was .87). SWAN also had excellent reliability in our sample (Cronbach’s alpha of .96). A forced two-factor solution provided a factor structure that aligned well with the ADHD-Inattentive and ADHD-Hyperactive/Impulsive subscales of SWAN. SWAN scores correlated with all reading measures, but not significantly with academic achievement, and the strength of this association got stronger from 2nd to 5th grade. The results suggest that ADHD-related symptoms and behavior hinder children from reaching their full reading fluency potential.This research was funded by The Icelandic Research Fund (Grants No. 174013-051, 195912-053) and the University of Iceland Research Fund.Accepted peer-reviewed chapte

Problems with visual statistical learning in developmental dyslexia

Previous research shows that dyslexic readers are impaired in their recognition of faces and other complex objects, and show hypoactivation in ventral visual stream regions that support word and object recognition. Responses of these brain regions are shaped by visual statistical learning. If such learning is compromised, people should be less sensitive to statistically likely feature combinations in words and other objects, and impaired visual word and object recognition should be expected. We therefore tested whether people with dyslexia showed diminished capability for visual statistical learning. Matched dyslexic and typical readers participated in tests of visual statistical learning of pairs of novel shapes that frequently appeared together. Dyslexic readers on average recognized fewer pairs than typical readers, indicating some problems with visual statistical learning. These group differences were not accounted for by differences in intelligence, ability to remember individual shapes, or spatial attention paid to the stimuli, but other attentional problems could play a mediating role. Deficiencies in visual statistical learning may in some cases prevent appropriate experience-driven shaping of neuronal responses in the ventral visual stream, hampering visual word and object recognition.This research was funded in part by a postdoctoral grant (Recruitment Fund of the University of Iceland) awarded to Heida Maria Sigurdardottir. Arni Kristjansson is funded by the Icelandic Research Fund (IRF), the Research Fund at the University of Iceland, and the European Research Council (ERC).Peer ReviewedRitrýnt tímari

Own-race and other-race face recognition problems without visual expertise problems in dyslexic readers

Post-print (lokagerð höfundar)Both intact and deficient neural processing of faces has been found in dyslexic readers. Similarly, behavioral studies have shown both normal and abnormal face processing in developmental dyslexia. We tested whether dyslexic adults are impaired in tests of own-race and other-race face recognition. As both face and word recognition rely considerably on visual expertise, we wished to investigate whether face recognition problems of dyslexic readers might stem from difficulties with experience-driven expert visual processing. We utilized the finding that people tend to be worse at discriminating other-race faces compared to own-race faces, the so-called other-race effect, thought to reflect greater experience with own-race faces. If visual expertise is compromised in dyslexic readers, so that their visual system is not effectively shaped by experience, then they might show a diminished other-race effect. Matched dyslexic and typical readers completed two tests of own- and other-race face recognition. The results show that dyslexic readers have problems with recognizing faces, and these difficulties are not fully accounted for by general problems with attention or memory. However, recognition is compromised for both own- and other-race faces, and the strength of the other-race effect does not differ between dyslexic and typical readers. There was individual variability in both groups, and an exploratory analysis revealed that while dyslexic readers with no university education showed deficits in face recognition, the dyslexic participants with higher education did not. We conclude that dyslexic readers as a group have face recognition problems. These are potentially modulated by educational level but compromised visual expertise cannot demonstrably account for the face recognition problems associated with dyslexia. We discuss the implications of these findings for theoretical accounts of dyslexia and for theories of word and face recognition.This work was supported by The Icelandic Research Fund (Grant No. 174013-051) and the University of Iceland Research Fund.Accepted peer-reviewed manuscrip

Laterality Effect (Face Perception)

Face recognition is an essential skill that in many species is associated with apparently specialized neurological and cognitive mechanisms. This chapter summarizes some of the behavioral and neuroscientific research on laterality effects in face perception, with a focus on face identity processing in humans and animals.This work was supported by The Icelandic Research Fund (Grant No. 174013-051) and the University of Iceland Research Fund

Dissociating the influence of visual and semantic properties on object foraging

In our previous study (unpublished data), we used a convolutional neural network (AlexNet trained on ecoset, layer 6; Mehrer et al., 2021), trained for object classification, to construct a two-dimensional visual object space (reference image set: extended BOSS image set (Bank of Standardized Stimuli; Brodeur et al., 2010; Brodeur et al., 2014) which we explored using psychophysics. In particular, we extracted two main visual dimensions explaining most variance (“animate-inanimate” and “stubby-spiky”), and projected images onto this space. This approach provides us with information about visual object properties, free from semantics and perceptual biases. We then administered a foraging task (N=73) where subjects clicked on each instance of one target object (e.g., toaster) but avoided any instance of another distractor object (e.g., television). The stimulus set included fake objects, real inanimate objects, and faces matched for visual qualities. We found that foraging speed correlated positively with target-distractor visual distances of fake objects, and to a lesser extent for real inanimate objects in the inanimate-stubby and inanimate-spiky quadrants of visual object space. Foraging speed was uncorrelated with visual distances of faces, and inversely related to visual distances for real inanimate objects within the animate part of object space, where objects had visual properties in contrast with their identity. In addition, we constructed a semantic object space for real inanimate objects to gain information about their semantic differences without the confound of visual factors. Semantic distances between object pairs explained additional variability in foraging speed in all cases. In summary, when people must discriminate between objects, visual qualities appear to be weighted highly for unknown objects lacking semantics. For real objects, some additional weight is put on semantic properties. In cases where an object’s appearance is in contrast with its identity, visual properties appear to be downweighted or even negatively weighed. In the current preregistered study (https://osf.io/g7kuy), our main aim is to confirm this last point by replicating and expanding on our previous study. To make sure that our previous results are not a peculiarity of the exact choices made, we use a different neural network architecture (VGG-16), a different reference image set (Animacy-Size), and different visual stimuli, as described below. The described paradigm and data should provide new insights into the factors that underlie object recognition

The effects of visuo-semantic clashes on object categorization

In our preregistered study, “Dissociating the influence of visual and semantic properties on object foraging” (https://osf.io/g7kuy), we used a convolutional neural network (CNN) trained for object classification, (VGG-16bn trained on ecoset, layer 15; Simonyan & Zisserman, 2014), to a construct two-dimensional visual object space. Using principal component analysis (PCA), we extracted two main visual dimensions explaining most variance, one of which approximates an animate-inanimate distinction. This approach provided us with information about visual object properties, free from human semantic and perceptual biases. We then projected various images onto this space and used them in a visual object foraging task, where participants searched for various instances of a particular image among various instances of a distractor image. In our two-dimensional object space, most inanimate objects map onto the inanimate part of object space, and most animals map onto the animate part of object space. However, some images are projected onto the “wrong” side of an animacy classification boundary, that is, an image of an animal is projected onto the inanimate part of object space, or an image of an inanimate object is projected onto the animate part of object space. In these instances, there is an incongruency between the identity of the image and its location in visual object space. We refer to this as a visuo-semantic clash. Our results (unpublished data) showed that when inanimate objects were projected onto the inanimate part of object space, there was a positive correlation between object space distance and foraging speed. However, this was not true when inanimate objects were projected onto the animate part of object space, producing a visuo-semantic clash. In other words, when objects do not look like what they are, according to CNNs, their visual similarities as operationally defined by distance in object space do not seem to matter for foraging efficiency. We did not find a clear effect of a visuo-semantic clash for animals. In the current experiment, we estimate whether people have difficulties categorizing images that produce a visuo-semantic clash in an object space derived from a CNN when image presentation is short and masked. We presume that under such circumstances, people have little opportunity for recurrent/feedback processing and will have to rely greatly on the initial sweep of feedforward visual information, which is misleading when images produce a visuo-semantic clash. We will present people with the same images of objects and animals as were used in our previous study (https://osf.io/g7kuy), at short and long presentation times, and ask them to indicate whether the image was of an animate or inanimate object. The described paradigm should provide us with further insights into object recognition in ambiguous settings

Faces and words are both associated and dissociated as evidenced by visual problems in dyslexia

Faces and words are traditionally assumed to be independently processed. Dyslexia is also traditionally thought to be a non-visual deficit. Counter to both ideas, face perception deficits in dyslexia have been reported. Others report no such deficits. We sought to resolve this discrepancy. 60 adults participated in the study (24 dyslexic, 36 typical readers). Feature-based processing and configural or global form processing of faces was measured with a face matching task. Opposite laterality effects in these tasks, dependent on left-right orientation of faces, supported that they tapped into separable visual mechanisms. Dyslexic readers tended to be poorer than typical readers at feature-based face matching while no differences were found for global form face matching. We conclude that word and face perception are associated when the latter requires the processing of visual features of a face, while processing the global form of faces apparently shares minimal – if any – resources with visual word processing. The current results indicate that visual word and face processing are both associated and dissociated – but this depends on what visual mechanisms are task-relevant. We suggest that reading deficits could stem from multiple factors, and that one such factor is a problem with feature-based processing of visual objects

Visual imagery vividness appears to be independent of perceptual and memory precision

Visual mental imagery, or the ability to see with the mind’s eye, varies between individuals. The vividness of visual imagery ranges from people with aphantasia who experience no mental image at all, to those with hyperphantasia who experience very clear and vivid mental 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 predicted that people experiencing weak or no mental imagery are poorer at retrieving information with great details from memory, such as the color of objects, than those experiencing strong and vivid mental imagery. This was tested in three experiments: a visual perception task, a visual working memory task, and a long-term visual memory task. The Vividness of Visual Imagery (VVIQ) questionnaire was used to assess imagery vividness. The perception task served as a control. A colored sample object and a grayscale test object were presented simultaneously. In the working memory and long-term memory tasks, a delay was added between the presentation of colored sample objects and grayscale test objects. Participants were asked to adjust the test object’s color until it matched that of the corresponding sample object. Our findings indicate no association between mental imagery vividness and memory precision. Possible explanations for this lack of an association are discussed