Previous research on mind wandering has used subjective verbal reports as a means to acquire the frequency and rate of its occurrence. I proposed the use of eye movements as an objective measure of mind wandering while participants attempted a reading task. Participants were placed in a self-classified probe-caught mind wandering paradigm while their eye movements were recorded. They were randomly probed every 2-3 minutes and were required to indicate whether their mind had been wandering before they were allowed to continue reading. The overall pattern showed that eye movement behaviour was slower and less frequent when participants reported mind wandering episodes, with duration and frequency of within-word regressions reaching levels of statistical significance. It may be that the cognitive processes that normally guide eye movements during reading exert less control during mind wandering episodes. Other implications and limitations are discussed.

Examining the neural correlates associated with the moment a stimulus enters or exits conscious awareness is one way to potentially identify the neural mechanisms that give rise to consciousness. In the present study, we examined neural activity using electroencephalogram (EEG) recordings while participants observed a bilateral shape-from-motion (SFM) display. While the display is in motion, the observer perceives an object that is immediately segregated from a noisy background. After the motion stops, the observer’s experience of the object remains momentarily in awareness, before it eventually fades out of consciousness back into the noisy background. Consistent with subjective reports of perceptual experience, we observed a prominent sustained posterior contralateral negativity (SPCN), but only in conditions associated with sustained awareness. Importantly, the amplitude of the SPCN was correlated with individual differences in visual awareness, suggesting that this activity plays a significant role in the maintenance of objects in consciousness.

Recent research has revealed many similarities between episodic memory, scene construction, and imagination of the future. It has been suggested that scene construction is the common process underlying memory and imagination, but no study to date has directly compared all three abilities. The present study compared retrieval time, ratings of detail and vividness for episodic memories, remembered scenes and imagined future events cued by landmarks of high and low familiarity. Memories, scenes, and imagined episodes based on a more familiar landmark as a cue were more quickly retrieved, more detailed, and more vivid. This study was the first to demonstrate the effects of frequent encounters with a cue on memory, scene construction and imagination of the future. Additionally, consistent results across conditions, as well as stronger effects in the scene construction condition, provide further evidence of a possible interdependence of episodic memory, imagination of the future, and scene construction.

Recent studies in rodents (McTighe et al, 2010; Burke et al, 2010) have suggested that forgetting is caused by the misidentification of novel stimuli as being familiar, matching the predictions of the representational-hierarchical model of Saksida & Bussey (2010). Here, we tested this idea in humans. Three groups of participants (young, healthy elders, elders at-risk for MCI) viewed novel and repeated stimuli in a continuous viewing task while their eye movements were recorded. According to the eye-movement based memory effect (Ryan et al, 2000) individuals make fewer fixations on items which are perceived as familiar. As interference increased, eye-movements directed to the novel stimuli declined, indicating these novel items were perceived as familiar. This effect was stronger in groups more vulnerable to interference (eg. at-risk elders). These results suggest that forgetting in humans, like rats, is driven by the misidentification of novel items as being familiar.

The current study investigates whether younger adults process distraction semantically and how age influences the level of distraction processing. In a first experiment, younger adults’ processing of distraction was examined by comparing implicit and explicit memory for that distraction. Then, in a second experiment, younger and older adults’ semantic processing of distractors was directly tested by examining memory for distractors on a conceptually based category-generation task. Younger adults showed equivalent implicit and explicit distractor memory in the first experiment and no conceptual priming for distractors on the category-generation task of the second experiment. Older adults, on the other hand, showed reliable conceptual priming for distractors, and the effect was significantly correlated with age in that group. The results collectively suggest that older, but not younger, adults engage in elaborate processing of irrelevant information, and that this effect is possibly tied to inhibitory control abilities that tend to decrease with age.

Convergent evidence suggests that the perirhinal cortex (PRC) is involved in perception, in addition to long-term memory, by representing higher-order object feature conjunctions. Recent functional magnetic resonance imaging (fMRI) investigations have shown greater PRC activity during the processing of objects with a higher versus lower degree of features in common, but notably, these studies have been limited to examining only two levels of feature overlap. To address this, we scanned neurologically healthy participants with fMRI during a 1-back working memory task for objects that possessed a very low, low, medium or high degree of feature overlap. Somewhat consistent with previous findings, trends towards greater PRC activity for high versus medium feature overlap objects, and for semantically identical compared to semantically different objects were observed. However, other aspects of our data, including diminished PRC activity during medium versus low feature overlap objects, are difficult to interpret and require further investigation.

The research focuses on the role of top-down influences on selective attention across the attentional visual field. The attentional visual field is the subset of the visual field in which attentional processes take place. The size of the attentional visual field is relatively large compared to the areas considered by most empirical studies of visual attention to date. Three possible forms of top-down influence are examined: 1) the expectation of the size of the area in which the target is likely to occur; 2) the expectation of the direction in which the target is likely to occur; and 3) existing unconscious bias in the spatial distribution of attention. Results from Experiment 1 suggest that participants modify the size of the attended area according to their expectation of the location of the target. Experiment 2 demonstrates that focus of attention can be oriented toward the expected target direction. Experiment 3 reveals that, even when no conscious control is involved, the distribution of attention is biased toward certain areas. Theoretical considerations are discussed, including the introduction of a simple statistical model to assist in conceptualizing the modifications of the distribution of attention over the attentional visual field. Practical applications of the results are also discussed.

This study used pre-existing data to examine whether children with ADHD, with and without working memory (WM) deficits, differ in their academic achievement and clinical profiles. 73 children (26% female), aged 6-12 years, with a confirmed diagnosis of ADHD had completed standardized achievement tests of reading, mathematics, and written language. Six WM measures and three parent and teacher questionnaires probing behaviour and executive functioning were administered. Of the sample, only 26% met the criteria for a WM deficit. Children with WM impairments were found to perform significantly worse than those without WM impairment on all achievement clusters, with no clinical profile differences. Poor WM is not universal in ADHD, but its presence is associated with lower academic achievement scores. Clinicians and educators should consider that underlying impairments in WM may be the contributing factors to academic difficulties in children with ADHD. Interventions targeting WM skills need to be implemented.

Behavioural symptoms, cognitive deficits, and findings from electrophysiological, neuroimaging and genetic studies all suggest atypical performance monitoring in ADHD. Performance monitoring involves error detection and post-error behavioural adjustment and is crucial to behavioural self-regulation and reinforcement learning, both of which are dysfunctional in ADHD. Therefore, post-error slowing was examined in children with ADHD and controls using a modified flanker task both with, and without, error detection provided. There was a significant main effect of group on post-error slowing across conditions and when error-detection was provided, significant post-error slowing deficits were found in children with ADHD. These findings suggest that the performance monitoring deficit in ADHD is specific to post-error behavioural adjustment and supports the inclusion of this deficit in the neurocognitive profile of ADHD. Findings are discussed in terms of current neurocognitive reinforcement learning models of ADHD.

In four experiments we used eye-tracking to investigate biases in looking behaviour during visual decision making tasks. In Experiment 1, participants viewed arrays of images of photographic art and decided which image was preferred (from a set of either two or eight alternatives). To analyze gaze behaviour during the decision we identified dwells (where a dwell is a series of consecutive fixations on a decision alternative). This analysis revealed two forms of gaze bias in the period prior to the response. Replicating prior findings (Shimojo, Simion, Shimojo, & Scheier, 2003), just prior to the response we found an increase in the frequency of dwells on the chosen item. In addition, throughout the decision, dwells on the chosen item were longer than dwells on other items. This pattern of biases was extremely similar across preference and non-preference decision instructions, but overall the biases were more pronounced in eight alternative decisions than in two alternative decisions. In Experiment 2 we manipulated the number of decision alternatives while controlling for differences in the stimulus displays. Participants viewed displays containing six everyday items, and chose either which of two sets of three items was the most expensive (two alternative set selection task) or which of the six items was the most expensive (six alternative item selection task). Consistent with Experiment 1, participants exhibited greater selectivity in their processing of stimulus information in the six alternative decisions compared to the two alternative decisions. In Experiments 3 and 4 we manipulated stimulus exposure in order to test predictions derived from the Gaze Cascade model (Shimojo et al., 2003). In Experiment 3, participants performed an eight alternative decision in which four of the items had been pre-exposed prior to the decision. In Experiment 4, stimulus exposure was manipulated during the ongoing decision using a gaze-contingent methodology. While these manipulations of stimulus exposure had strong effects on gaze bias, the specific predictions of the model were not supported. Rather, we suggest an interpretation based on prior research, according to which the gaze bias reflects the selective processing of stimulus information according to its relevance to the decision task.