Research shows that children often confuse facial expressions of fear with surprise and disgust with anger. According to the perceptual-attentional limitations hypothesis, facial expressions are confused because they share action units (Camras, 1980; Wiggers, 1982). Experiment 1 tested this hypothesis for the confusion between fear and surprise and Experiment 2 for the confusion between disgust and anger. Eye movements were monitored in both experiments. In experiment 1, the results showed that children were more accurate when two distinctive action units were presented than when the brow lowerer was the only distinctive action unit differentiating between fear and surprise. Furthermore, the results showed that participants spent more time fixating on the mouth than the eyebrows. They made more saccades when the only distinctive cue was in the eyebrows. In experiment 2, participants identified the emotion as anger when the mouth was open, and disgust when the mouth was closed, spending more time on the mouth when the mouth was open. These findings suggest that facial expressions are confused, not only because of the amount of visual similarities they share, but also because children do not allocate their attention to facial regions equally; they tend to focus on the mouth.

This thesis investigates sensorimotor adaptive mechanisms that maintain the accuracy of goal-directed saccades in amblyopia, a developmental disorder characterized by impairment of spatiotemporal visual processing. Saccadic adaptation was induced by displacing the visual target toward initial fixation during the saccade. Eleven visually normal controls and seven patients with amblyopia were tested binocularly and monocularly with the amblyopic and fellow eye (non-dominant and dominant eye in controls) in three separate sessions. Patients with amblyopia exhibited reduced adaptation of saccadic gain compared to controls when viewing with the amblyopic eye and binocularly. Initiation of saccades was also delayed in patients when viewing with the amblyopic eye. It is proposed that the adaptive ability to modify the initial saccadic motor commands for maintaining short-term saccadic accuracy is impaired in amblyopia due to imprecise error signals. Moreover, this thesis reaffirms the notion that the error signals driving saccadic adaptation are visual in nature.

This thesis investigates sensorimotor adaptive mechanisms that maintain the accuracy of goal-directed saccades in amblyopia, a developmental disorder characterized by impairment of spatiotemporal visual processing. Saccadic adaptation was induced by displacing the visual target toward initial fixation during the saccade. Eleven visually normal controls and seven patients with amblyopia were tested binocularly and monocularly with the amblyopic and fellow eye (non-dominant and dominant eye in controls) in three separate sessions. Patients with amblyopia exhibited reduced adaptation of saccadic gain compared to controls when viewing with the amblyopic eye and binocularly. Initiation of saccades was also delayed in patients when viewing with the amblyopic eye. It is proposed that the adaptive ability to modify the initial saccadic motor commands for maintaining short-term saccadic accuracy is impaired in amblyopia due to imprecise error signals. Moreover, this thesis reaffirms the notion that the error signals driving saccadic adaptation are visual in nature.

Being able to predict the goal of other people’s actions is an important aspect of our daily lives. This ability allows us to interact timely with others and adjust our behaviour appropriately. The general aim of the present thesis was to explore which processes best explain our ability to predict other people’s action goals during development. There are different theories concerning this ability. Some stress the fact that observation of others actions activate the same areas of the brain involved in our own action production, this way helping us to understand what they are doing. Other theories suggest that we understand actions independently of our own motor proficiency. For example, the ability to predict other peoples’ action goals could be based on visual experience seeing others actions acquired trough time or on the assumption that actions will be performed in a rational way. The studies included in this thesis use eye tracking to study infants’ and adults’ action prediction during observation of goal directed actions. Prediction is operationalized as predictive gaze shifts to the goal of the action. Study I showed that infants are sensitive to the functionality of hand configuration and predict the goal of reaching actions but not moving fists. Fourteen-month-olds also looked earlier to the goal of reaching actions when the goal was to contain rather than displace, indicating that the overarching goal (contain/displace) impact the ability to predict local action goals, in this case the goal of the initial reaching action. Study II demonstrated that 6-month-olds, an age when infants have not yet started placing objects into containers, did not look to the container ahead of time when observing another person placing objects into containers. They did, however, look to the container ahead of time when a ball was moving on its own. The results thus indicate that different processes might be used to predict human actions and other events. Study III showed that 8-month-old infants in China looked to the mouth of an actor eating with chopsticks ahead of time but not when the actor was eating with a spoon. Swedish infants on the other hand looked predictively to the mouth when the actor was eating with a spoon but not with chopsticks. This study demonstrates that prediction of others’ goal directed actions is not simply based on own motor ability (as assumed in Study I and II) but rather on a combination of visual/cultural experience and own motor ability. The results of these studies suggest that both own motor proficiency as well as visual experience with observing similar actions is necessary for our ability to predict other people’s action goals. These results are discusses in the light of a newer account of the mirror neuron system taking both statistical regularities in the environment and own motor capabilities into account.

This thesis presents for the first time a symmetrical, bilateral model of central pathways in the vestibulo-ocular reflex (VOR), based on known neural pathways and their interconnections on both sides of the brainstem. The model explains, simultaneously, the known behaviour of individual neural groups within the system (in central pathways) and of eye movements at its output. It does not require a long time constant "neural integrator" (NI) nor separate pathways for the generation of slow and fast phases of nystagmus, as in previous models. A single "neural filter" (NF, time constant < 1s) on each side of the brainstem is sufficient to provide integration in the slow phase mode, with the help of a positive feedback loop due to commissural innervation. Fast/slow phase alternation of eye movements is achieved through simple modulation of commissural inhibition by reticular burst cells. / Analytic and computer simulation studies show that the model can account, for the first time, for published response characteristics in the vestibular nuclei, and for their dependence on commissural and cerebellar pathways.

There is growing evidence that young adult readers frequently fail to create exhaustive textbased representations as they read. Although there has been a significant amount of research devoted to age-related effects on text processing, there has been little research concerning this so-called shallow processing by older readers. This dissertation uses eye tracking to explore age-related effects in shallow processing across different levels of text representations. Experiment 1 investigated shallow processing by older readers at the textbase level by inserting semantic anomalies into passages read by participants. Older readers frequently failed to report the anomalies, but no more frequently than did younger readers. The eye-fixation behaviour revealed that older readers detected some of the anomalies sooner than did younger readers, but had to allocate disproportionately more processing resources to looking back to the anomalies to achieve comparable levels of detection success as their younger counterparts. Experiment 2 examined age-related effects of shallow processing at the surface form by inserting syntactic anomalies into passages read by older and younger adults. Older readers were less likely to detect syntactic anomalies when first encountering them relative to younger readers and engaged in increased regressive fixations to the anomalies. However, older readers with high iii reading comprehension skill were able to use their familiarity with text content to increase their likelihood of syntactic anomaly detection. Experiment 3 investigated the role of aging on shallow processing of the temporal dimension of the situation model. No age-related differences reporting the anomalies were found. The eye-fixation behaviour revealed that older readers with high working memory capacity detected some anomalies sooner than did younger readers; however, they had to allocate increased processing resources looking back to the anomalies to achieve comparable levels of detection as younger readers. Together, the results demonstrate that older readers are susceptible to shallow processing, but no more so than younger readers when they can rely on their linguistic skill or their existing knowledge to help reduce processing demands. However, older readers appear to require additional processing time to achieve comparable levels of anomaly detection as younger readers.

Competing models of eye movement control during reading disagree over the extent to which eye movements reflect ongoing linguistic and lexical processing, as opposed to visual/oculomotor factors (for reviews, see Rayner, 1998, 2009a). To address this controversy, participants’ eye movements were monitored in four experiments that manipulated a wide range of lexical variables. Specifically, Experiment 1 manipulated contextual predictability by presenting target words (e.g., teeth) in a high-predictability prior context (e.g. “The dentist told me to brush my teeth to prevent cavities.”) versus a low-predictability prior context (e.g., “I'm planning to take better care of my teeth to prevent cavities.”), Experiment 2 manipulated lexical ambiguity by presenting biased homographs (e.g., bank, crown, dough) in a subordinate-instantiating versus a dominant-instantiating prior context, and Experiments 3A and 3B manipulated word frequency by contrasting high frequency target words (e.g., table) and low frequency target words (e.g., banjo). In all four experiments, I used distributional analyses to examine the time-course of lexical influences on fixation times. Ex-Gaussian fitting (Staub, White, Drieghe, Hollway, & Rayner, 2010) revealed that all three lexical variables (i.e., predictability, lexical ambiguity, word frequency) were fast-acting enough to shift the entire distribution of fixation times, and a survival analysis technique (Reingold, Reichle, Glaholt, & Sheridan, 2012) revealed rapid lexical effects that emerged as early as 112 ms from the start of the fixation. Building on these findings, Experiments 3A and 3B provided evidence that lexical processing is delayed in an unsegmented text condition that contained numbers instead of spaces (e.g., “John4decided8to5sell9the7table2in3the9garage6sale”), relative to a normal text condition (e.g., “John decided to sell the table in the garage sale”). These findings have implications for ongoing theoretical debates concerning eye movement control, lexical ambiguity resolution, and the role of interword spaces during reading. In particular, the present findings provide strong support for models of eye movement control that assume that lexical influences can have a rapid influence on the majority of fixation durations, and are inconsistent with models that assume that fixation times are primarily determined by visual/oculomotor constraints.

Competing models of eye movement control during reading disagree over the extent to which eye movements reflect ongoing linguistic and lexical processing, as opposed to visual/oculomotor factors (for reviews, see Rayner, 1998, 2009a). To address this controversy, participants’ eye movements were monitored in four experiments that manipulated a wide range of lexical variables. Specifically, Experiment 1 manipulated contextual predictability by presenting target words (e.g., teeth) in a high-predictability prior context (e.g. “The dentist told me to brush my teeth to prevent cavities.”) versus a low-predictability prior context (e.g., “I'm planning to take better care of my teeth to prevent cavities.”), Experiment 2 manipulated lexical ambiguity by presenting biased homographs (e.g., bank, crown, dough) in a subordinate-instantiating versus a dominant-instantiating prior context, and Experiments 3A and 3B manipulated word frequency by contrasting high frequency target words (e.g., table) and low frequency target words (e.g., banjo). In all four experiments, I used distributional analyses to examine the time-course of lexical influences on fixation times. Ex-Gaussian fitting (Staub, White, Drieghe, Hollway, & Rayner, 2010) revealed that all three lexical variables (i.e., predictability, lexical ambiguity, word frequency) were fast-acting enough to shift the entire distribution of fixation times, and a survival analysis technique (Reingold, Reichle, Glaholt, & Sheridan, 2012) revealed rapid lexical effects that emerged as early as 112 ms from the start of the fixation. Building on these findings, Experiments 3A and 3B provided evidence that lexical processing is delayed in an unsegmented text condition that contained numbers instead of spaces (e.g., “John4decided8to5sell9the7table2in3the9garage6sale”), relative to a normal text condition (e.g., “John decided to sell the table in the garage sale”). These findings have implications for ongoing theoretical debates concerning eye movement control, lexical ambiguity resolution, and the role of interword spaces during reading. In particular, the present findings provide strong support for models of eye movement control that assume that lexical influences can have a rapid influence on the majority of fixation durations, and are inconsistent with models that assume that fixation times are primarily determined by visual/oculomotor constraints.

In four experiments on insight problem solving, we investigated the time course of the development of solution knowledge prior to response, as well as the impact of stimulus familiarity on task performance and eye movement measures. In each experiment, participants solved anagram problems while their eye movements were monitored. In Experiments 1a and 1b, each anagram problem consisted of a circular array of letters: a scrambled four-letter solution word containing three consonants and one vowel, and an additional randomly-placed distractor consonant. Viewing times on the distractor consonant compared to the solution consonants provided an online measure of knowledge of the solution. Viewing times on the distractor consonant and the solution consonants were indistinguishable early in the trial. In contrast, several seconds prior to the response, viewing times on the distractor consonant decreased in a gradual manner compared to viewing times on the solution consonants. Importantly, this pattern was obtained across both trials in which participants reported the subjective experience of insight and trials in which they did not. These findings are consistent with the availability of partial knowledge of the solution prior to such information being accessible to subjective phenomenal awareness. In Experiments 2 and 3, each anagram problem consisted of a centrally located three-letter string plus three additional individual letters located above and to the side of the central letter string. All the letters in the central letter string were members of the five-letter solution word, while one of the individual letters was a randomly placed distractor. In Experiment 2, we replicated our findings of the gradual development of solution knowledge using this more complex stimulus display. In Experiment 3, we manipulated the familiarity of the central letter string by presenting it either in the form of a three-letter word, or as a meaningless string of letters. Behavioural measures showed an overall negative impact of familiarity on task performance, while eye movement measures revealed a more complex pattern of effects, including both interference and facilitation. Critically, the effects of familiarity on problem solving did not interact with the development of solution knowledge prior to response.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.