Two-hand line-bisection task outcomes correlate with several measures of hemisphericity

While seeking new functional methods to reassess the concept of hemisphericity, a two-hand line-bisection task was investigated because of reports of large, stable differences among the general population. These were found to be due to hemispheric differences in judgment of the midpoint of horizontal lines, made visible due to the unilateral brain control of each hand. By use of a two-hand line-bisection test (Best-Hand Test), university workers (n=412) were readily sorted into theoretical response categories, resulting in the production of two large groups. These two groups correlated well with those produced by four independent hemisphericity assessments, two physiological and two psychological. This is the third biophysical method whose performance-based group separations significantly correlated with those produced by preference-based hemisphericity-type questionnaires. It is rapid and avoids language, education, or cultural bias.     

The role of memory in the Tower of London task

The Tower of London (TOL) task is widely used as a neuropsychological test of planning. Relatively little is known of the cognitive components of the task, and in particular the role of memory in performance. The current studies on normal adults looked at the role of verbal and spatial working memory in the TOL. The effects of verbal and visuospatial dual-task manipulations on TOL performance were examined in an experiment with 36 participants. Both verbal and visuospatial executive secondary tasks caused poorer performance on the TOL; however, concurrent articulatory suppression enhanced performance. The results suggest that executive and spatial components are important in the task, and raise questions about the role of preplanning in the TOL.     

Fluency versus conscious recollection in category-production performance: the performance of schizophrenic patients

The purpose of this study was to investigate the relative contribution in schizophrenics of automatic processes (fluency) and conscious processes (conscious recollection) for the control of preencoded material in category production tasks. In one condition (Exclusion condition), subjects were told specifically not to produce previously presented words during the category-production task. This condition was compared with a standard category-production task in which subjects were told to produce the six first words that came to mind for a semantic category (Inclusion condition). In the inclusion condition, the effects of conscious control and automatic processes operated in the same direction, whereas in the exclusion condition automatic influences and conscious control were opposed. A recognition task followed the category-production tasks. Since the exclusion condition required conscious control of encoded items, we hypothesized that schizophrenic patients would be less able than control subjects to avoid producing study list items. These results indicated that schizophrenics' performance differed from these of control subjects in the exclusion condition but not in inclusion condition. Recognition performance was similar in both the schizophrenic and the control groups. These results suggest a defective conscious control in schizophrenic patients and confirm the data from the literature on explicit memory in these patients.     

Experimentally manipulating the effects of involuntary conscious memory on a priming task

Recent studies showed that involuntary conscious memory can enhance priming in implicit tasks. However, because the results of these studies were based on post hoc selection methods in which subjects were assigned to conditions (aware or unaware) based on their responses on a posttest questionnaire, it is possible that subject selection effects may have influenced the results. The present study used a novel method that experimentally manipulated the effects of involuntary conscious memory on a word stem task. This was accomplished by inducing the experience of word recollection in one test condition while inhibiting it in another. This study showed that subjects who experienced word recollection showed significantly higher rates of priming than those who did not. The results represent the first purely experimental demonstration of involuntary conscious memory's ability to affect priming on implicit tasks.     

The role of overt rehearsal in enhanced conscious memory for emotional events

This study tested the hypothesis that overt rehearsal is sufficient to explain enhanced memory associated with emotion by experimentally manipulating rehearsal of emotional material. Participants viewed two sets of film clips, one set of emotional films and one set of relatively neutral films. One set of films was viewed in each of two sessions, with approximately 1 week between the sessions. Participants were given a free recall test of all of films viewed approximately 1 week after the second session. Rehearsal was manipulated by instructing one group of participants not to discuss the films with anyone (no talk group) and instructing a second group to discuss both sets of films with at least three people (forced talk group). A third group consisted of participants instructed not to discuss the films with anyone, but who did not comply with these instructions (talkers group). All groups recalled significantly more of the emotional films than the neutral films. Furthermore, the relative number of emotional and neutral films recalled did not differ significantly among the three groups. The results indicate that overt rehearsal is insufficient to explain the enhancing effects of emotion on memory.     

The role of verbal short-term memory in task selection: How articulatory suppression influences task choice in voluntary task switching

The roles of verbal short-term memory (vSTM) in task selection and task performance processes were examined when individuals were asked to voluntarily choose which of two tasks to perform on each trial randomly. Consistent with previous voluntary task-switching (VTS) research, we hypothesized that vSTM would support random task selection by maintaining a sequence of previously executed tasks that would be used by a representativeness heuristic. Furthermore, because using a representativeness heuristic requires sufficient time for updating and comparison processes, we expected that vSTM would have a greater effect on task selection when more time was available. Participants completed VTS under concurrent articulatory suppression and foot tapping at short and long response-to-stimulus intervals (RSIs). Task selection in VTS was more repetitive under suppression than under foot tapping, but this effect did not vary with RSI, suggesting that vSTM does not maintain the sequence of executed tasks to guide task selection. Instead, vSTM is critical for maintaining the intended task and ensuring that it is carried out. In contrast to the finding that a working memory load impairs task performance, we found no difference in reaction times and no switch costs between suppression and foot-tapping conditions, suggesting that vSTM is not critical for task performance.     

Developmental change in young children's use of haptic information in a visual task: the role of hand movements

Preschoolers who explore objects haptically often fail to recognize those objects in subsequent visual tests. This suggests that children may represent qualitatively different information in vision and haptics and/or that children’s haptic perception may be poor. In this study, 72 children (2½-5 years of age) and 20 adults explored unfamiliar objects either haptically or visually and then chose a visual match from among three test objects, each matching the exemplar on one perceptual dimension. All age groups chose shape-based matches after visual exploration. Both 5-year-olds and adults also chose shape-based matches after haptic exploration, but younger children did not match consistently in this condition. Certain hand movements performed by children during haptic exploration reliably predicted shape-based matches but occurred at very low frequencies. Thus, younger children’s difficulties with haptic-to-visual information transfer appeared to stem from their failure to use their hands to obtain reliable haptic information about objects.     

The role of working memory capacity and interference resolution mechanisms in task switching

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response–distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. A total of 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response–distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores, which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching.     

The hare and the snail: Dissociating visual orienting from conscious perception

A method for investigating attentional effects of peripheral visual objects, independently of perceptual identification, is described. We report an experiment using this method which shows that visual processing of peripheral objects differs radically, depending on whether participants move attention in response to an object or consciously perceive that object. When luminance contrast was reduced, conscious perceptual discrimination of peripheral letters was massively slower and less accurate—but both low and high contrast letters elicited rapid attentional orienting effects and these rapid orienting effects were equal in magnitude across low and high contrast. This pattern is consistent with known differences in luminance sensitivity between the dorsal and ventral visual processing streams, and with rapid dorsal–ventral interaction mediated via re-entrant feedback. Our findings show that the control system responsible for rapid movements of attention is exquisitely sensitive to visual form information at low levels of contrast, and involves a different neurocognitive pathway to that which gives rise to conscious perception.     

Age-related differences in the brain areas outside the classical language areas among adults using category decision task

Older adults perform much like younger adults on language. This similar level of performance, however, may come about through different underlying brain processes. In the present study, we evaluated age-related differences in the brain areas outside the typical language areas among adults using a category decision task. Our results showed that similar activation patterns were found in classical language processing areas across the three age groups although regional lateralization indices in Broca’s and Wernicke’s areas decreased with age. The greatest differences, however, among the three groups were found primarily in the brain areas not associated with core language functioning including the hippocampus, middle frontal gyrus, ventromedial frontal cortex, medial superior parietal cortex and posterior cingulate cortex. Therefore, the non-classical language areas may exhibit an age-related difference between three age groups while the subjects show a similar activation pattern in the core, primary language processing during a semantic decision task.     

Viewing artworks: Contributions of cognitive control and perceptual facilitation to aesthetic experience

When we view visual images in everyday life, our perception is oriented toward object identification. In contrast, when viewing visual images as artworks, we also tend to experience subjective reactions to their stylistic and structural properties. This experiment sought to determine how cognitive control and perceptual facilitation contribute to aesthetic perception along with the experience of emotion. Using functional MRI, we show that aesthetic perception activated bilateral insula which we attribute to the experience of emotion. Moreover, while adopting the aesthetic orientation activated the left lateral prefrontal cortex, paintings that facilitated visuospatial exploration activated the left superior parietal lobule. The results suggest that aesthetic experience is a function of the interaction between top-down orienting of attention and bottom-up perceptual facilitation.     

The role of metacognition in prospective memory: Anticipated task demands influence attention allocation strategies

The present study investigates how individuals distribute their attentional resources between a prospective memory task and an ongoing task. Therefore, metacognitive expectations about the attentional demands of the prospective-memory task were manipulated while the factual demands were held constant. In Experiments 1a and 1b, we found attentional costs from a prospective-memory task with low factual demands to be significantly reduced when information about the low to-be-expected demands were provided, while prospective-memory performance remained largely unaffected. In Experiment 2, attentional monitoring in a more demanding prospective-memory task also varied with information about the to-be-expected demands (high vs. low) and again there were no equivalent changes in prospective-memory performance. These findings suggest that attention–allocation strategies of prospective memory rely on metacognitive expectations about prospective-memory task demands. Furthermore, the results suggest that attentional monitoring is only functional for prospective memory to the extent to which anticipated task demands reflect objective task demands.     

The role of short-term memory capacity and task experience for overconfidence in judgment under uncertainty

Research with general knowledge items demonstrates extreme overconfidence when people estimate confidence intervals for unknown quantities, but close to zero overconfidence when the same intervals are assessed by probability judgment. In 3 experiments, the authors investigated if the overconfidence specific to confidence intervals derives from limited task experience or from short-term memory limitations. As predicted by the naive sampling model (P. Juslin, A. Winman, & P. Hansson, 2007), overconfidence with probability judgment is rapidly reduced by additional task experience, whereas overconfidence with intuitive confidence intervals is minimally affected even by extensive task experience. In contrast to the minor bias with probability judgment, the extreme overconfidence bias with intuitive confidence intervals is correlated with short-term memory capacity. The proposed interpretation is that increased task experience is not sufficient to cure the overconfidence with confidence intervals because it stems from short-term memory limitations.     

Expectation creates something out of nothing: The role of attention in iconic memory reconsidered

Conscious experience is modulated by attention and expectation, yet is believed to be independent of attention. The experiments on iconic memory (IM) are usually taken as support for this claim. However, a recent experiment demonstrated that when attention is diverted away from the IM letter display subjects fail to see the absence of IM letters. Here we contribute to the ongoing debate by overcoming experimental shortcomings of this previous experiment, by measuring subjective visibility and by testing the effect of the post-cue. We were able to replicate these earlier findings and extend them by demonstrating that subjects who do not realize the absence of letters perceive illusory letters. This result means that there is still phenomenal consciousness, even when attention is diverted. Expectation creates illusory content that overwrites valid IM content. Taken together these findings suggest that the present experimental paradigm is not appropriate to make claims about IM content.     

A naturalistic study of prospective memory in preschoolers: The role of task interruption and motivation

We conducted two naturalistic experiments to investigate preschoolers’ development of event-based prospective memory (PM) and to examine the effects of motivation and interruption of an ongoing task. Children aged 2–6 years were asked to perform familiar PM tasks while engaged in their habitual kindergarten play. PM performance improved systematically across the preschool years. The type of PM response (motor or verbal) did not affect performance. High motivation was necessary for 2-year-olds to perform well, and it remained an important factor that increased performance across the entire preschool age range. The need to interrupt an ongoing activity decreased performance in 3-, 4-, and 5-year-olds, but not in children aged 2 or 6 years. The pattern of results is consistent with explanations for interruption effects that highlight the role of inhibitory control.     

The development of hand preference in children: The effect of task demands and links with manual dexterity

Lateralisation of hand preference and manual dexterity are known to develop over childhood, while in adulthood strength of hand preference has been shown to interact with extrinsic task demands. Some evidence exists to suggest that strength of hand preference and motor skill may be related. In the current study a handedness inventory, midline crossing (QHP) and peg-moving tasks were used to investigate: (1) the development of hand preference between 4 and 11 years; (2) whether extrinsic task demands affect strength of hand preference, and (3) whether strength of hand preference was associated with manual dexterity. Younger children (4–5 years) showed weak hand preference in comparison to older children (8–11 years), and extrinsic task demands influenced willingness to cross the body’s midline with the preferred hand. Age and peg-moving speed were associated with midline crossing in certain task conditions. Overall, results suggest a coupling between manual dexterity and brain maturation in typical development.     

The role of working memory in information acquisition and decision making: Lessons from the binary prediction task

The effects of memory constraints upon information acquisition and decision making were examined in two experiments using binary prediction tasks, where participants observe outcomes for two options before deciding which one to bet upon. Our studies extend previous investigations to the case where participants learn the structure of the task through observation, but where information acquisition is separated from the task of prediction. Participants with higher cognitive capacity (larger memory span or higher intelligence) were more likely to adopt the “maximizing” strategy (always selecting the more frequent alternative). This finding conflicts with some recent investigations of similar tasks, a contrast that implies that the presence of feedback on choices may be important in determining the strategic actions of high-capacity individuals. Participants selecting the optimal strategy were in turn more efficient in their data acquisition. The behaviour of participants adopting suboptimal choice strategies was consistent with prediction based upon a “narrow window of experience”—that is, seeking to match the characteristics of small samples of observations.     

The task rule congruency effect in task switching reflects activated long-term memory

Reaction time task rule congruency effects (RT-TRCEs) reflect faster responses to stimuli for which the competing task rules indicate the same correct response than to stimuli indicating conflicting responses. The authors tested the hypothesis that RT-TRCE reflects activated overlearned response category codes in long-term memory (such as up or left). The results support the hypothesis by showing that (a) RT-TRCE was absent for tasks for which there were no response codes ready beforehand, (b) RT-TRCE was present after these tasks were practiced, and (c) these practice effects were found only if the tasks permitted forming abstract response category codes. The increase in the RT-TRCE with response slowness, found only for familiar tasks, suggests that the abstract response category codes may be verbal or linguistic in these cases. The results are discussed in relation to task-switching theories and prefrontal functions.     

Complex prospective memory: development across the lifespan and the role of task interruption

Prospective memory (PM) reflects the product of cognitive processes associated with the formation, retention, delayed initiation, and execution of intentions. It has been proposed that developmental changes in PM across the lifespan are heavily dependent upon the developmental trajectory of executive control functions. This study is the first to apply a complex PM task to children, young adults, and older adults. The procedure allows for the assessment of each of the 4 phases of PM. During intention execution, the authors additionally manipulated whether participants had to actively interrupt attention to the current 'ongoing' task in order to switch to the execution of the next intended task. Group differences mirroring inverted U-shaped functions were observed in those phases conceptualized as relying on executive control (intention formation, initiation, and execution). Age differences in intention execution were substantially greater when active task interruption was necessary. The current study provides the first evidence of growth and decline of complex PM across the lifespan and suggests that the degree of inhibitory control needed to succeed in the task may be one factor underlying this development.     

The effects of load variability in short-term memory task

Six groups of Ss viewed briefly exposed arrays of letters, half designated high-valued and half low-valued. Immediately after each exposure Ss wrote down as many of the stimuli as they could remember. For three groups, the number of letters in each exposure was constant from trial to trial; for the remaining three groups, the number of letters in each exposure varied from trial to trial. This tested the hypothesis that load variability influences the development of an efficient response strategy which, in turn, affects the processing of information stored in short-term memory. The data supported this hypothesis. Performance was superior under the constant load condition due to the ability of these Ss to correctly report both high- and low-valued letters. Poor performance was observed under the variable load condition because of a decrease in the number of low valued letters correctly reported.