Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Applied Vision Association Christmas Meeting, Leuven, Belgium 19–20 December 2013

For about 15 years, we have been attempting to create a software system (EvoFIT) that produces an identifiable composite when constructed of an unfamiliar face after a long retention interval (as is the usual case in police investigations). EvoFIT has now been shown to be effective in police field trials and has been used in 20 police forces. More recently, some developments have been very effective on their own to improve composite quality—these include: (a) encouraging constructors to focus on the overall (global) properties of the face during the initial interview (Holistic CI, H-CI), (b) constructing internal features first (masking external features), and (c) presenting composites for naming using a perceptual image-stretch format. In the current project, we explored whether these techniques would produce even more identifiable composites when combined. Forty participants looked at a video of an unfamiliar target face and, 24 hours later, received an interview to obtain a description of the face (either CI/ H-CI) and then constructed a composite using EvoFIT (either blurry externals/internals-only). Further participants were presented with the resulting composites to name, first front-on (the usual way to view the face) and then by looking at the face sideways (perceptual stretch). The three techniques were effective independently, replicating past research, but together produced composites with an effect that was more than just additive—to yield a mean naming level of 74% correct. A composite system using all three of these techniques would therefore appear to be effective for police-work

Lateralised repetition priming for face recognition: priming occurs in the right hemisphere only

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Target Selection and Enhancement During Attentional Tracking

At any waking moment, we are bombarded with more sensory information than we can fully process. Attention is necessary to deal with the dynamic world we live in. One fundamental function of vision and attention is to keep track of moving objects, but what are the targets of attention during tracking? One of the first theories of attentional tracking predicted that targets would be selected at early processing stages. By employing the double-drift illusion, which dissociates physical and perceived positions of moving objects, we investigated which of these positions is selected for tracking. Contrary to earlier theories and in line with newer findings, targets were selected rather late in visual processing, at least after the construction of illusory percepts, for both covert (Chapter One) and overt tracking (Chapter Two). Furthermore, capacity and speed limits to attentional tracking are hemifield specific. Brain activity in many areas is known to covary with the number of tracked targets, but it was previously unknown whether this effect would also show hemifield bias. Only targets presented in the contralateral hemifield influenced activity in earlier visual areas, while both contralateral and ipsilateral targets affected activity in parietal and frontal areas associated with attention (Chapter Three). Due to the hemifield specific nature of the capacity limit, we conjecture that it should emerge where load dependent activity is strongly contralateral. Overall, the studies presented in this dissertation illuminate two different aspects of attentional tracking. While selection happens late in the visual hierarchy, capacity and speed limits appear to emerge early in visual processing

Perceptual organization and its influence upon attention

Humans are able to control so much of their environment not through brute strength or enhanced sensory receptors, but through our ability to understand the world around us. In order to make sense of the world around us we need to organize the information that our sensory systems receive. One of the most fundamental steps in this organizational process lies in the construction of objects. By breaking down our sensory input into objects the mind provides a basis upon which it can begin to scaffold our understanding of the world. This thesis therefore explores the basic stages at which the visual system organizes our sensory input into distinct objects. It explores these stages by exploiting the fact that the brain’s limited processing resources can be selectively allocated on the basis of ‘object-hood’. This allocation of processing resources, or attention, on the basis of these early stages of segmentation is commonly referred to as ‘object based attention’. ‘Object based attention’ and perceptual organisation are explored in three sections in this thesis: Understanding the Phenomenon of Object Based Attention. The first three chapters of this thesis seeks to further our understanding of the phenomenon of ‘object based attention’, for example, chapter 3 explores whether the visual system can simultaneously parse several objects as potential units of attention, or whether it can only segment one or two objects at a time. Object Based Attention, a Tool to Explore the Nature of Perceptual Organisation The second section of this thesis attempts to use the phenomenon of ‘object based attention’ as a tool to explore the nature of perceptual representations, for example chapter 5 tests whether different modalities (in particular vision and touch) are able to directly share information about objects in order to build up an integrated model of the external world. Object Based Attention, Perceptual Organisation and Shape Processing Area LO. In the final section of this thesis the nature of perceptual organization is explored in a patient with a very specific form of brain damage that enables us to ask what areas of the brain are critically required for different aspects of perceptual organization

Targets but not flankers are suppressed in crowding as revealed by EEG frequency tagging

Perception of a visual target can strongly deteriorate in the presence of flanking elements (crowding). For example, adding lines next to a vernier makes vernier offset discrimination difficult. Crowding is often considered a bottleneck of low-level vision, determined by the unavoidable limitations of the early visual system. In accordance with this proposal, neural processing of the flankers should be impaired in crowding as much as that of the target. To test this prediction, we used steady-state visually evoked potentials (ssVEPs) to separate target responses from flanker responses. We presented a vernier target either alone or flanked by lines, which had the same color as the vernier or a different color. Crowding by same-color flankers was stronger than by different-color flankers. Mirroring the behavioral results, ssVEP amplitudes corresponding to the target were higher for different-color flankers than for same-color flankers. Flanker related ssVEPs, however, did not depend on crowding strength. It seems that target, but not flanker processing, is susceptible to crowding. In line with previous results, we suggest that crowding is not caused by low-level interferences but is linked to target-flanker grouping instead

A ciência da leitura e a produção acadêmica: caminhos trilhados

Linguistics focuses on the different phenomena of language. In macrolinguistics areas, there is Psycholinguistics. This subfield researches (de)coding processes of messages with verbal codes. Thus, one of its influential fields of activity is reading. Reading is one of the most complex information processing tasks. It begins with the graphemes decoding and it finishes with the text comprehension. Regarding the assessment of reading, there are several exams and large-scale tests, such as Pisa, Saeb (Aneb and Anresc/Prova Brasil), ENEM. Alarming statistics come with the indicators from these evaluative instruments. There are, among Brazilians, low levels of reading comprehension and marked functional illiteracy rate. Therefore, this study aimed to research what scientific communication has shared in terms of knowledge about reading. Specifically, the objectives were synthesize, considering the psycholinguistic approach of reading research, studies and research with the most recurrent theme in the reading field evidenced from the electronic communication, in order to investigate the dimensions and limitations of knowledge about this subject. For this, through WebQualis system, Qualis A1 and A2 scientific journals with electronic format and with focuses/scopes related to reading from the areas of (1) Language Arts/Linguistics, (2) Psychology and (3) Education were selected. With the selected journals and through Capes Journals Portal, all their volumes and issues from 2011 to 2015 were analyzed. With this, scientific articles related to reading were mapped. With the mapped articles abstracts, the recurrent themes in reading in the scientific production were observed. Finally, with the full articles that had the recurrent theme, the researches results were integrated, synthesizing and pondering about them. With a critical-reflexive assessment of the data, relevant information was found. First, on one hand, it was noted that the reading has achieved a stable and upward space through the electronic communication. On the other one, it was checked that the contributions of Psychology have a great influence in reading and comprehension research. Second, it was shown that the most frequent theme in electronic productions is comprehension. Finally, with the synthesis, it was found that, increasingly, comprehension topics related to reading neurobiological aspects were empirical and directly investigated. In addition, there are several studies that propose reading teaching methods as well as strategies for improving the comprehension, including the use of TICs. Moreover, it was found that many research results are limited. This is because the comprehension involves several components – cognitive processes and skills. Researches often focus attention on one or the other component of it only, and each research fixes a specific methodology design and that vary considerabably. Regarding the assessment of reading, many of the methodological apparatus tasks evaluate only the product of comprehension and not its process. In other words, built mental representations are evaluated and not how the encoding of this text occurred. Therefore, in short, both the researches advancement in the comprehension field and several limitations were observed.A Linguística atém-se aos mais diferentes fenômenos da língua(gem). Nos domínios macrolinguísticos, há a Psicolinguística. Essa subárea tem como foco de investigação os processos de (de)codificação de mensagens de códigos verbais. Assim, um de seus influentes campos de atuação é o de leitura. A leitura é uma das tarefas de processamento de informações mais complexas. Ela tem como princípio a decodificação grafêmica e como fim a compreensão textual. Em relação à avaliação da leitura, existem diversos testes e provas em larga escala, como o Pisa, o Saeb (Aneb e Anresc/Prova Brasil), o ENEM. Com os indicadores desses instrumentos avaliativos, vêm estatísticas alarmantes. Há, entre os brasileiros, baixos níveis de compreensão leitora e acentuado índice de analfabetismo funcional. Por conseguinte, este trabalho pretendeu investigar o que a comunicação científica tem compartilhado em termos de conhecimento sobre leitura. Especificamente, objetivou-se sintetizar, considerando a abordagem psicolinguística de investigação da leitura, estudos e pesquisas cuja temática evidenciada da comunicação eletrônica fosse a mais recorrente no campo da leitura, a fim de investigar dimensões e limitações do conhecimento a respeito dessa temática. Para isso, selecionaram-se, por meio do sistema WebQualis, periódicos científicos Qualis A1 e A2 em formato eletrônico e com focos/escopos relacionados à leitura, das áreas de (1) Letras/Linguística, (2) Psicologia e (3) Educação. Com os periódicos selecionados e por meio do Portal de Periódicos Capes, analisaram-se todos os seus volumes e números de 2011 a 2015, a fim de mapear artigos científicos com assunto em leitura. Com os resumos dos artigos mapeados, evidenciaram-se temáticas mais recorrentes na produção científica em leitura. Por fim, dos artigos completos cuja temática era a mais recorrente, integraram-se resultados das pesquisas, fazendo-se uma análise, com fins de síntese e reflexão. Da apreciação crítico-reflexiva dos dados, constataram-se relevantes informações. Em primeiro lugar, de um lado, observou-se que a leitura tem conquistado um estável e ascendente espaço em meio à comunicação eletrônica. De outro, demonstrou-se que contribuições da Psicologia têm forte influência na pesquisa de leitura e compreensão. Em segundo, evidenciou-se que a compreensão é a temática mais frequente nas produções eletrônicas. Por fim, com a síntese, constatou-se que, cada vez mais, se investiga empírica e diretamente facetas da compreensão em relação às bases neurobiológicas da leitura. Igualmente, há diversas pesquisas que propõem metodologias de ensino da leitura, bem como estratégias para a melhoria da compreensão, incluindo a utilização das TICs. Além disso, concluiu-se que muitos resultados de pesquisas são limitados. Isso porque a compreensão envolve diversos componentes – processos cognitivos e habilidades. E as pesquisas, muitas vezes, apenas focam a atenção em um ou em outro componente, além de definirem específicos e variados designs de metodologia. Em relação à avaliação da leitura, muitas das tarefas do aparato metodológico das pesquisas apenas avaliam o produto da compreensão e não o seu processo. Ou seja, avaliam-se representações mentais construídas e não como ocorreu a codificação desse texto na mente do leitor. Por conseguinte, em suma, tanto o avanço de pesquisas no campo de compreensão quanto, também, diversas limitações ficaram evidentes

Sensory and cognitive factors in multi-digit touch, and its integration with vision

Every tactile sensation – an itch, a kiss, a hug, a pen gripped between fingers, a soft fabric brushing against the skin – is experienced in relation to the body. Normally, they occur somewhere on the body’s surface – they have spatiality. This sense of spatiality is what allows us to perceive a partner’s caress in terms of its changing location on the skin, its movement direction, speed, and extent. How this spatiality arises and how it is experienced is a thriving research topic, compelled by growing interest in the nature of tactile experiences from product design to brain-machine interfaces. The present thesis adds to this flourishing area of research by examining the unified spatial quality of touch. How does distinct spatial information converge from separate areas of the body surface to give rise to our normal unified experience of touch? After explaining the importance of this question in Chapter 1, a novel paradigm to tackle this problem will be presented, whereby participants are asked to estimate the average direction of two stimuli that are simultaneously moved across two different fingerpads. This paradigm is a laboratory analogue of the more ecological task of representing the overall movement of an object held between multiple fingers. An EEG study in Chapter 2 will reveal a brain mechanism that could facilitate such aggregated perception. Next, by characterising participants’ performance not just in terms of error rates, but by considering perceptual sensitivity, bias, precision, and signal weighting, a series of psychophysical experiments will show that this aggregation ability differs for within- and between-hand perception (Chapter 3), is independent from somatotopically-defined circuitry (Chapter 4) and arises after proprioceptive input about hand posture is accounted for (Chapter 5). Finally, inspired by the demand for integrated tactile and visual experience in virtual reality and the potential of tactile interface to aid navigation, Chapter 6 will examine the contribution of tactile spatiality on visual spatial experience. Ultimately, the present thesis will reveal sensory factors that limit precise representation of concurrently occurring dynamic tactile events. It will point to cognitive strategies the brain may employ to overcome those limitations to tactually perceive coherent objects. As such, this thesis advances somatosensory research beyond merely examining the selectivity to and discrimination between experienced tactile inputs, to considering the unified experience of touch despite distinct stimulus elements. The findings also have practical implications for the design of functional tactile interfaces

Visual attention in primates and for machines - neuronal mechanisms

Visual attention is an important cognitive concept for the daily life of humans, but still not fully understood. Due to this, it is also rarely utilized in computer vision systems. However, understanding visual attention is challenging as it has many and seemingly-different aspects, both at neuronal and behavioral level. Thus, it is very hard to give a uniform explanation of visual attention that can account for all aspects. To tackle this problem, this thesis has the goal to identify a common set of neuronal mechanisms, which underlie both neuronal and behavioral aspects. The mechanisms are simulated by neuro-computational models, thus, resulting in a single modeling approach to explain a wide range of phenomena at once. In the thesis, the chosen aspects are multiple neurophysiological effects, real-world object localization, and a visual masking paradigm (OSM). In each of the considered fields, the work also advances the current state-of-the-art to better understand this aspect of attention itself. The three chosen aspects highlight that the approach can account for crucial neurophysiological, functional, and behavioral properties, thus the mechanisms might constitute the general neuronal substrate of visual attention in the cortex. As outlook, our work provides for computer vision a deeper understanding and a concrete prototype of attention to incorporate this crucial aspect of human perception in future systems.:1. General introduction 2. The state-of-the-art in modeling visual attention 3. Microcircuit model of attention 4. Object localization with a model of visual attention 5. Object substitution masking 6. General conclusionVisuelle Aufmerksamkeit ist ein wichtiges kognitives Konzept für das tägliche Leben des Menschen. Es ist aber immer noch nicht komplett verstanden, so dass es ein langjähriges Ziel der Neurowissenschaften ist, das Phänomen grundlegend zu durchdringen. Gleichzeitig wird es aufgrund des mangelnden Verständnisses nur selten in maschinellen Sehsystemen in der Informatik eingesetzt. Das Verständnis von visueller Aufmerksamkeit ist jedoch eine komplexe Herausforderung, da Aufmerksamkeit äußerst vielfältige und scheinbar unterschiedliche Aspekte besitzt. Sie verändert multipel sowohl die neuronalen Feuerraten als auch das menschliche Verhalten. Daher ist es sehr schwierig, eine einheitliche Erklärung von visueller Aufmerksamkeit zu finden, welche für alle Aspekte gleichermaßen gilt. Um dieses Problem anzugehen, hat diese Arbeit das Ziel, einen gemeinsamen Satz neuronaler Mechanismen zu identifizieren, welche sowohl den neuronalen als auch den verhaltenstechnischen Aspekten zugrunde liegen. Die Mechanismen werden in neuro-computationalen Modellen simuliert, wodurch ein einzelnes Modellierungsframework entsteht, welches zum ersten Mal viele und verschiedenste Phänomene von visueller Aufmerksamkeit auf einmal erklären kann. Als Aspekte wurden in dieser Dissertation multiple neurophysiologische Effekte, Realwelt Objektlokalisation und ein visuelles Maskierungsparadigma (OSM) gewählt. In jedem dieser betrachteten Felder wird gleichzeitig der State-of-the-Art verbessert, um auch diesen Teilbereich von Aufmerksamkeit selbst besser zu verstehen. Die drei gewählten Gebiete zeigen, dass der Ansatz grundlegende neurophysiologische, funktionale und verhaltensbezogene Eigenschaften von visueller Aufmerksamkeit erklären kann. Da die gefundenen Mechanismen somit ausreichend sind, das Phänomen so umfassend zu erklären, könnten die Mechanismen vielleicht sogar das essentielle neuronale Substrat von visueller Aufmerksamkeit im Cortex darstellen. Für die Informatik stellt die Arbeit damit ein tiefergehendes Verständnis von visueller Aufmerksamkeit dar. Darüber hinaus liefert das Framework mit seinen neuronalen Mechanismen sogar eine Referenzimplementierung um Aufmerksamkeit in zukünftige Systeme integrieren zu können. Aufmerksamkeit könnte laut der vorliegenden Forschung sehr nützlich für diese sein, da es im Gehirn eine Aufgabenspezifische Optimierung des visuellen Systems bereitstellt. Dieser Aspekt menschlicher Wahrnehmung fehlt meist in den aktuellen, starken Computervisionssystemen, so dass eine Integration in aktuelle Systeme deren Leistung sprunghaft erhöhen und eine neue Klasse definieren dürfte.:1. General introduction 2. The state-of-the-art in modeling visual attention 3. Microcircuit model of attention 4. Object localization with a model of visual attention 5. Object substitution masking 6. General conclusio