O problema desta pesquisa se configura em analisar as variáveis envolvidas no aprendizado da resposta de observação visual apropriada em arranjos com diferentes variações de estímulos irrelevantes e as implicações deste aprendizado para o estabelecimento da discriminação. O aprendizado da resposta de observação apropriada não vem apenas expor o animal aos estímulos especificados, no sentido de que o animal passa a atentar a eles, mas envolve o aprendizado sobre a relevância desses estímulos e, simultaneamente faz com que o animal deixe de atentar e a responder aos estímulos irrelevantes. No que se refere ao estabelecimento da discriminação, este problema de pesquisa foi tratado prioritariamente no período pressolução. Ampla extensão do período pressolução ou mesmo falhas no estabelecimento da discriminação podem ser determinadas por falhas no aprendizado sobre a relevância dos estímulos discriminativos. Nesse sentido, o procedimento proposto objetiva analisar o papel dos estímulos irrelevantes sobre a distribuição das respostas de observação e o aprendizado daquela que foi definida como apropriada em função dos estímulos discriminativos. A análise foi realizada em tarefas de discriminação simultânea com diferentes variações de pares de estímulos irrelevantes. Estas variações foram apresentadas para quatro grupos de oito participantes cada. Estas variações foram apresentadas na seguinte ordem: Constante (Grupo Const) Inter-tentativas (Grupo Inter) Intra-tentativas (Grupo Intra) Variações combinadas (Grupo Comb). Os resultados mostraram que a extensão do período pressolução para os Grupos Intra e Comb foi maior do que para os Grupos Const e Inter. Inversamente, a distribuição da observação para os estímulos discriminativos foi menor para os Grupos Intra e Comb em comparação aos demais grupos nas três primeiras tentativas. Algumas questões foram fundamentais para a análise e a discussão sobre o aprendizado da resposta de observação apropriada a partir de diferentes arranjos de estímulos e em função das consequências diferenciais. Entre elas, o papel mediador da última observação entre as diferentes consequências e a variação e modelagem das respostas de observação. Discutiu-se que houve situações onde o aprendizado sobre a irrelevância dos estímulos bem como situações onde o aprendizado sobre a relevância dos estímulos foi requerido. O requerimento deste aprendizado afetou o aprendizado da resposta de observação apropriada / The problem of this research is to analyze the variables involved in appropriate visual observing learning in arrangements with different variations of irrelevant stimuli and its implications for the discrimination establishment. The learning of the observing response comes not only expose the animal to discriminative stimuli in the sense that the animal begins to pay attention to them, but involves learning about the relevance of these stimuli. Simultaneously the animal ignores the irrelevant stimuli. Wide extension of the pre-solution period can be determined by failures in learning about the relevance of the discriminative stimuli. In this sense, the procedure aims to analyze the role of irrelevant stimuli on the distribution of observing responses. The analysis was performed in simultaneous discrimination tasks with different variations of irrelevant stimuli. These variations were made for four groups of each eight participants. These variations were presented in the following order: Constant (Group Const) - Inter-trials (Group Inter) - Intra-trials (Group Intra) combined variations (Group Comb). The results showed that the extent of pre-solution period for Intra and Comb groups was greater than for Const and Inter Groups. Conversely, the distribution of the observation to the discriminative stimuli was smaller for Intra and Comb groups compared to the other groups in the first three trials. Some issues were central in order to analyze the appropriated observing learning for example the role of last observing and the different consequences. There were situations where learning about the irrelevance was required. Learning about the irrelevance affected the appropriate observing response learning

In this study, we investigated what informational aspects of faces could account for the ability to match an individual’s face to their voice, using only static images. In each of the first six experiments, we simultaneously presented one voice recording along with two manipulated images of faces (e.g. top half of the face, bottom half of the face, etc.), a target face and distractor face. The participant’s task was to choose which of the images they thought belonged to the same individual as the voice recording. The voices remained un-manipulated. In Experiment 7 we used eye tracking in order to determine which informational aspects of the model’s faces people are fixating while performing the matching task, as compared to where they fixate when there are no immediate task demands. We presented a voice recording followed by two static images, a target and distractor face. The participant’s task was to choose which of the images they thought belonged to the same individual as the voice recording, while we tracked their total fixation duration. In the no-task, passive viewing condition, we presented a male’s voice recording followed sequentially by two static images of female models, or vice versa, counterbalanced across participants. Participant’s results revealed significantly better than chance performance in the matching task when the images presented were the bottom half of the face, the top half of the face, the images inverted upside down, when presented with a low pass filtered image of the face, and when the inner face was completely blurred out. In Experiment 7 we found that when completing the matching task, the time spent looking at the outer area of the face increased, as compared to when the images and voice recordings were passively viewed. When the images were passively viewed, the time spend looking at the inner area of the face increased. We concluded that the inner facial features (i.e. eyes, nose, and mouth) are not necessary informational aspects of the face which allow for the matching ability. The ability likely relies on global features such as the face shape and size. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

The Where's Waldo problem concerns how individuals can rapidly scan a scene to detect a target object in it. This dissertation develops the ARTSCAN Search neural model to clarify how brain mechanisms that govern spatial and object attention, spatially-invariant object learning and recognition, reinforcement learning, and eye movement search are coordinated to enable learning and directed search for desired objects at specific locations in a cluttered scene. In the model, interactions from the Where cortical processing stream to the What cortical processing stream modulate invariant category learning of a desired object, whereas interactions from the What cortical processing stream to the Where cortical processing stream support search for the object. In particular, when an invariant object category representation is activated top-down by a cognitive plan or by an active motivational source in the model's What stream, it can shift spatial attention in the Where stream and thereby selectively activate the locations of sought-after object exemplars. These combined What-to-Where and Where-to-What interactions clarify how the brain's solution of the Where's Waldo problem overcomes the complementary deficiencies of What and Where stream processes taken individually by using inter-stream interactions that allow both invariant object recognition and spatially selective attention and action to occur.

Estudos anteriores chamam a atenção para a importância da resposta de observação para o estabelecimento da discriminação em um treino de reforçamento diferencial. A presente pesquisa tem por objetivo analisar a resposta de observação e o movimento dos olhos em uma situação de discriminação simples simultânea. Participaram desta pesquisa seis adultos. Como estímulos, foram utilizadas imagens com alterações da tela Don Quixote, pintada por Pablo Picasso. Duas imagens foram apresentadas simultaneamente, ao longo de tentativas discretas. Em cada tentativa, houve uma imagem na presença do qual a resposta foi reforçada, bem como uma imagem na presença do qual a resposta não foi reforçada. O experimento foi dividido em três fases. Uma Fase Pré-experimental, uma Fase Experimental e uma Fase Pós-experimental. Na Fase Pré-experimental, foram apresentadas duas imagens idênticas. Na Fase Experimental, primeiramente, foram apresentadas as imagens com uma diferença localizada na parte superior esquerda de uma delas. Posteriormente, a diferença foi deslocada para a parte inferior esquerda e finalmente, a diferença foi apresentada na parte superior direita. O conjunto das condições da Fase Experimental previu o estabelecimento de novas discriminações ao modificar as propriedades diferenciais das imagens. Na Fase Pós-experimental, foram novamente apresentadas duas imagens inteiramente idênticas, as mesmas da Fase Pré-experimental. Para o registro do movimento dos olhos, durante todas as fases, foi utilizado um equipamento de rastreamento do olhar. Para efeito de análise, a imagem como um todo foi dividida, primeiramente, em três partes: parte 1 a área que circunscreve a diferença apresentada na Condição 1 ; parte 2 a área que circunscreve a diferença apresentada na Condição 2; e parte 3 a área que circunscreve a diferença apresentada na Condição 3. Após esta divisão, foi analisada a distribuição da duração do olhar entre as partes ao longo de todas as fases. Todos os participantes apresentaram um responder discriminado que se replicou nas três condições sucessivas. Um primeiro padrão observado na distribuição da duração do olhar para os três participantes é que, na Fase Pré-experimental, todos olharam a) por mais tempo para o Dom Quixote, b) por um tempo intermediário para o Sancho Pança e c) por menos tempo para o Sol. Estes padrões se repetiram, com pequenas alterações, ao longo das condições experimentais e na última fase. Nas condições experimentais, durante a discriminação, o que pôde ser observado é que a duração de olhar para as partes das imagens que possuíam a propriedade relevante para a discriminação foi elevada enquanto a duração de olhar para outras partes diminuiu. Todos os participantes apresentaram uma duração de observação maior para o S+ do que para o S, observação seletiva. Os dados sobre as respostas manuais na tarefa foram discutidos a partir do aprendizado cumulativo, learning set e do controle de estímulos. Os dados sobre a distribuição do olhar foram discutidos a partir de seu estabelecimento enquanto resposta de observação, sua extinção e ressurgência. / Previous studies draw attention to the importance of observing response to the discrimination establishment in differential reinforcement training. This research aims to analyze the observing response and eye movement in a simultaneous simple discrimination situation. Six adults participated. Images of Don Quixote screen painted by Pablo Picasso were used as stimuli. Two images were presented simultaneously along discrete trials. The experiment was divided in three phases: Pre-experimental Phase, Experimental Phase and Post-experimental Phase. In Pre-experimental phase, two identical images were presented. In the Experimental Phase, the images were displayed with a difference at the top left of it. Subsequently the difference was moved to its bottom left portion and finally the difference was displayed on its upper right. The set of conditions of the Experimental Phase predicted the establishment of new discriminations. In Post-experimental Phase, two identical images were presented again. The picture was divided in three parts: Part 1 - the area surrounding the difference displayed in Condition 1; Part 2 - the area surrounding the difference displayed in Condition 2; and Part 3 - the area surrounding the difference displayed in Condition 3. After this division, the duration of looking at these parts was analyzed throughout all phases. All participants showed discriminative performance in three successive conditions. During the Pre-experimental Phase, all participants: a) spent more time looking at Don Quixote, b) spent an intermediary time looking at Sancho Pança, and c) spent a shot time looking at Sol. These patterns were repeated with minor changes along the experimental conditions and the last phase. Under the experimental conditions the duration of looking at the parts of the images whose property was relevant to the discrimination increased while the duration of looking at other parts decreased. All participants showed an increased duration of looking at the S + than at the S- (selective observing). The manual responses were discussed in terms of learning set and stimulus control. The distribution of looking at was discussed in terms of its establishment as an observing response, its extinction and resurgence.

The electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. The 12-lead ECG shows this activity in 12 "views" called "leads", relative to the location of sensors attached to the body surface. The ECG is a routinely applied cost effective diagnostic medical test, utilised in healthcare settings around the world. Although more than three hundred million ECGs are recorded each year, correctly interpreting them is considered a complex task. Failure to make correct interpretations can lead to injury or death and costs vast sums in litigation payments. Many automated attempts at interpreting ECGs have been implemented and continue to be developed and improved. Despite this, automated methods are still considered to be less reliable than expert human interpretation. As ECG interpretation is both a cognitive and visual task, eye-tracking holds great potential as an investigative methodology. This thesis aims to identify any cues in visual behaviour that may indicate differences in subsequent ECG interpretation accuracy. This is the first work that uses eye-tracking to analyse how practitioners interpret ECGs as a function of accuracy. In order to investigate these phenomenon, several experiments were carried out using eye-movements captured from clinical practitioners that interpret ECGs as part of their usual clinical role. The findings presented in this thesis have advanced research in the understanding of ECG interpretation. Specifically: Clinical history makes a difference to how people look at ECGs; different gaze patterns are often found in accurate and inaccurate interpretation groups. Grouping data to account for within ECG lead behaviour (eye-movement patterns within a lead) is more revealing than analysis at the level of the lead (eye-movements between leads). Findings suggest analysing visual behaviour at this level is crucial in order to detect behaviour in ECG interpretation. Further to this the thesis presents eye-tracking techniques that can be applied to wider areas of task performance. These methods work over complex stimuli, are able to deal post hoc with differently sized groups and generate appropriate areas of interest on a stimulus. These methods detect important differences in eye-movement behaviour between groups that are missed when applying standard inferential statistical techniques.

Estudos anteriores chamam a atenção para a importância da resposta de observação para o estabelecimento da discriminação em um treino de reforçamento diferencial. A presente pesquisa tem por objetivo analisar a resposta de observação e o movimento dos olhos em uma situação de discriminação simples simultânea. Participaram desta pesquisa seis adultos. Como estímulos, foram utilizadas imagens com alterações da tela Don Quixote, pintada por Pablo Picasso. Duas imagens foram apresentadas simultaneamente, ao longo de tentativas discretas. Em cada tentativa, houve uma imagem na presença do qual a resposta foi reforçada, bem como uma imagem na presença do qual a resposta não foi reforçada. O experimento foi dividido em três fases. Uma Fase Pré-experimental, uma Fase Experimental e uma Fase Pós-experimental. Na Fase Pré-experimental, foram apresentadas duas imagens idênticas. Na Fase Experimental, primeiramente, foram apresentadas as imagens com uma diferença localizada na parte superior esquerda de uma delas. Posteriormente, a diferença foi deslocada para a parte inferior esquerda e finalmente, a diferença foi apresentada na parte superior direita. O conjunto das condições da Fase Experimental previu o estabelecimento de novas discriminações ao modificar as propriedades diferenciais das imagens. Na Fase Pós-experimental, foram novamente apresentadas duas imagens inteiramente idênticas, as mesmas da Fase Pré-experimental. Para o registro do movimento dos olhos, durante todas as fases, foi utilizado um equipamento de rastreamento do olhar. Para efeito de análise, a imagem como um todo foi dividida, primeiramente, em três partes: parte 1 a área que circunscreve a diferença apresentada na Condição 1 ; parte 2 a área que circunscreve a diferença apresentada na Condição 2; e parte 3 a área que circunscreve a diferença apresentada na Condição 3. Após esta divisão, foi analisada a distribuição da duração do olhar entre as partes ao longo de todas as fases. Todos os participantes apresentaram um responder discriminado que se replicou nas três condições sucessivas. Um primeiro padrão observado na distribuição da duração do olhar para os três participantes é que, na Fase Pré-experimental, todos olharam a) por mais tempo para o Dom Quixote, b) por um tempo intermediário para o Sancho Pança e c) por menos tempo para o Sol. Estes padrões se repetiram, com pequenas alterações, ao longo das condições experimentais e na última fase. Nas condições experimentais, durante a discriminação, o que pôde ser observado é que a duração de olhar para as partes das imagens que possuíam a propriedade relevante para a discriminação foi elevada enquanto a duração de olhar para outras partes diminuiu. Todos os participantes apresentaram uma duração de observação maior para o S+ do que para o S, observação seletiva. Os dados sobre as respostas manuais na tarefa foram discutidos a partir do aprendizado cumulativo, learning set e do controle de estímulos. Os dados sobre a distribuição do olhar foram discutidos a partir de seu estabelecimento enquanto resposta de observação, sua extinção e ressurgência. / Previous studies draw attention to the importance of observing response to the discrimination establishment in differential reinforcement training. This research aims to analyze the observing response and eye movement in a simultaneous simple discrimination situation. Six adults participated. Images of Don Quixote screen painted by Pablo Picasso were used as stimuli. Two images were presented simultaneously along discrete trials. The experiment was divided in three phases: Pre-experimental Phase, Experimental Phase and Post-experimental Phase. In Pre-experimental phase, two identical images were presented. In the Experimental Phase, the images were displayed with a difference at the top left of it. Subsequently the difference was moved to its bottom left portion and finally the difference was displayed on its upper right. The set of conditions of the Experimental Phase predicted the establishment of new discriminations. In Post-experimental Phase, two identical images were presented again. The picture was divided in three parts: Part 1 - the area surrounding the difference displayed in Condition 1; Part 2 - the area surrounding the difference displayed in Condition 2; and Part 3 - the area surrounding the difference displayed in Condition 3. After this division, the duration of looking at these parts was analyzed throughout all phases. All participants showed discriminative performance in three successive conditions. During the Pre-experimental Phase, all participants: a) spent more time looking at Don Quixote, b) spent an intermediary time looking at Sancho Pança, and c) spent a shot time looking at Sol. These patterns were repeated with minor changes along the experimental conditions and the last phase. Under the experimental conditions the duration of looking at the parts of the images whose property was relevant to the discrimination increased while the duration of looking at other parts decreased. All participants showed an increased duration of looking at the S + than at the S- (selective observing). The manual responses were discussed in terms of learning set and stimulus control. The distribution of looking at was discussed in terms of its establishment as an observing response, its extinction and resurgence.

Doctor of Philosophy / Department of Psychological Sciences / Lester C. Loschky / Visual resolution (i.e., blur or clarity) is a natural aspect of vision. It has been used by film makers to direct their audience’s attention by focusing the depth of field such that the critical region in a scene is uniquely clear and the surrounding is blurred. Resolution contrast can focus attention towards unique clarity, as supported by previous eye tracking and visual search research (Enns & MacDonald, 2013; Kosara, Miksch, Hauser, Schrammel, Giller, & Tscheligi, 2002; & McConkie, 2002; Peterson, 2016; Smith & Tadmor, 2012). However, little is known about how unique blur is involved in guiding attention (e.g., capture, repel, or be ignored). Peterson (2016) provided reaction time (RT) evidence that blur is ignored by selective attention when resolution is not task-relevant. Perhaps visual resolution is a search asymmetry where unique clarity can be used to guide selective attention during search, but unique blur cannot guide attention. Yet, perhaps the RT evidence was not sensitive enough with Peterson’s (2016) methodology to observe unique blur capturing or repelling attention. Eye movements (e.g., letter first fixated) may be more sensitive than RT as it measures blur and clarity’s influence on guiding attention earlier in a trial. The current study conducted three experiments that investigated: a) how visual resolution guides attention when it is task-irrelevant (Exp. 1), b) whether visual resolution is a search asymmetry, by manipulating resolution’s task-relevance (Use Blur, Use Clarity, Do Not Use Unique Blur or Clarity, & No Instructions) (Exp. 2), and c) whether blur and/or clarity are processed preattentively or require attention (Exp. 3). Experiments 1 and 2 manipulated blur and clarity (Exp. 1 Resolution = Task-irrelevant & Exp. 2 Resolution = Task-relevant), during a rotated L and T visual search measuring RT and eye movements. Experiment 1 found with the more sensitive eye movement measures that unique clarity strongly captured attention while unique blur weakly repelled attention towards nearby clarity (or clarity, especially that close to blur, captured attention). Experiment 2 found evidence that visual resolution is not a search asymmetry because the influence of resolution on selective attention was contingent upon its task-relevance, which theoretically supports the presence of a reconfigurable resolution feature detector. Experiment 3 used a feature search for either blur or clarity (i.e., resolution was task-relevant) and compared RT x Set Size search slopes. Both blurred and clear target present RT x Set Size search slopes were ~ 1 msec/item. The results strongly supported that blur and clarity are both processed preattentively, and provided additional evidence that resolution is not a search asymmetry. Overall, the current studies shed light on how visual resolution is processed and guides selective attention. The results revealed that visual resolution is processed preattentively and has a dynamic relationship with selective attention. Predicting how resolution will guide attention requires knowledge of whether resolution is task relevant or irrelevant. By increasing our understanding of how resolution contrast guides attention, we can potentially apply this knowledge to direct viewers’ attention more efficient using computer screens and heads-up displays.

This thesis explores the relationship between fixation location and the locus of attention during reading. Early theories of eye movement control during reading suggested that a very tight coupling exists between the two (Just & Carpenter, 1980); however, it has since been shown that dissociations do exist. Whether these dissociations necessarily implicate parallel lexical processing, or whether they can be accommodated for within a serial-sequential framework is explored in a series of experiments. Experiment 1 tested whether parallel lexical processing is, at the very least, psychologically plausible. Two horizontally aligned letter strings were presented simultaneously on a screen, the task being to decide whether they were physically identical or not. Even when presentation duration should have been short enough to prohibit the strictly serial processing of each word in turn, the results show clear lexical effects: high frequency words were responded to faster and with fewer errors than low frequency words. Effects of lexicality and orthography were also found. These results suggest that the two words had been processed at a lexical level in an overlapping fashion. Experiments 2 and 3 investigated the nature and range of word n+2 preview effects. In Experiment 2, word n+1 was either a determiner or 3-letter alternative higher frequency word; in Experiment 3, word n+1 was either a 4- or a 6-letter high frequency word. A gaze contingent display change technique was employed, where prior to passing an invisible boundary located immediately after word n, one, the other, neither or both of words n+1 and n+2 received a nonword preview. In addition to showing orthographic parafoveal-on-foveal effects stemming from word n+1, there was also evidence that word n+2 preview influenced targeting decisions on words n and n+1. Word n+2 preview effects are also found on word n+2 and in the spillover region. These effects were most wide ranging when word n+1 length was an average of 5- compared to 3-letters. Higher-level plausibility preview effects were explored in Experiments 4-6, again using a gaze contingent display change technique. In Experiment 4 word n+1 received either an identical preview, a different but plausible one, or an anomalous, or nonword preview. Critically, an effect of plausibility arose on word n+1, with anomalous previews receiving longer inspection times than alternative plausible previews. Experiments 5 and 6 investigated the range over which these effects might occur, testing for a plausibility preview effect on word n+2. Results showed numerical, but not statistical evidence for a plausibility-related preview effect on word n+2. There were, however, clear orthographic word n+2 preview effects. Finally, Experiment 7 experimentally tested the immediate oculomotor response to a mislocated fixation, using a text shift paradigm to simulate saccadic error and measuring the effect on lexical processing. Critically, this experiment showed that a quick error correction strategy appears to be engaged following a simulated saccadic undershoot, rather than a stay and process response. This suggests that a mislocated fixation account coupled with a stay and process response is unlikely to provide a viable explanation for lexical parafoveal-on-foveal effects. Overall, it is suggested that current instantiations of both serial (e.g., Reichle, Warren & McConnell, 2009) and parallel (e.g., Schad & Engbert, 2012) models of eye movement control during reading appear to fail to capture major aspects of these patterns of results. The results do, however, appear to fit most parsimoniously with a perspective on eye movement control that allows for multiple words to be processed in an overlapping fashion.

Distraction during driving is one of the leading contributors to injury and mortality rates in traffic accidents. The aim of this current thesis was to consider 1) whether oculomotor and electrophysiological metrics could act as markers of cognitive distraction; 2) whether decrements in hazard perception performance caused by secondary cognitive task demand are to some extent due to cognitive load interfering with processes of alerting, orienting, inhibitory control and visual search; 3) what elements of secondary cognitive tasks have the greatest impact on hazard perception performance; and 4) whether the susceptibility of previously identified markers of cognitive distraction are affected by primary task difficulty. Over the course of four Experiments we recorded the effects of secondary cognitive task demand on behavioural, oculomotor and electrophysiological metrics during a variety of low-level and complex visual tasks. Taken together the experiments of this thesis have demonstrated that secondary cognitive task demand interferes with not just one but every component process of hazard perception performance that was examined. Next, this research has demonstrated that measures such as blink rates, saccade peak velocities, the spread of fixations along the horizontal axis as well as reductions in alpha and beta power output may be reliable indicators of secondary cognitive task demand regardless of the type of primary task. Finally we have shown that the co-registration of eye movements, EEG and ERP measures is a viable method with which to study the cognitive processes involved in visual processing within low level and complex visual tasks.

All current theories of spoken word recognition (e.g., Allopenna et al., 1998; McClelland & Elman, 1986; Norris, 1994) suggest that any part of a target word triggers activation of candidate words. Visual world paradigm studies have relied on the linking hypothesis that the probability of looking at the referent of a word directly tracks the word’s level of activation (e.g., Allopenna et al., 1998). However, how much information is needed to trigger a saccade to a visual representation of the word’s referent? To address this question, the present study manipulated the number and location of shared segments between the target and competitor words. Experimental evidence is provided by two visual world paradigm experiments on Japanese, using natural and synthesized speech. In both experiments, cohort competitor pictures were not fixated more than unrelated distractor pictures unless the cohort competitor shares the initial CVC with the target. Bayesian analyses provide strong support for the null hypothesis that shorter overlap does not affect eye movements. The results suggest that a listener needs to accumulate enough evidence for a word before a saccade is generated. The human data were validated by an interactive computational model (TRACE: McClelland & Elman, 1986). The model was adapted to Japanese language to examine whether the TRACE model predicts competitor effects that fit human data. The model predicted that there should be effects when words share any amount with a target which confirms the current theory. However, the model did not fit the human data unless there is longer overlap between words. This indicates that eye movements are not as closely tied to fixation probabilities of lexical representations as previously believed. The present study suggests that looking at a referent of a word is a decision, made when the word’s activation exceeds a context-specific threshold. Subthreshold activations do not drive saccades. The present study conclude that decision-making processes need to be incorporated in models linking word activation to eye movements.