Children's level of participation in a false-belief task, age, and theory of mind

The hide-and-seek deception task of M. Chandler, A. S. Fritz, and S. Hala (1989) was modified to provide a more precise estimate of the age at which children acquire and manifest a theory of mind. Two characters (good, bad) and two levels of involvement (pretend play, sociodramatic play) were incorporated into the research design, so that children's representational understanding of deception could be studied. Two-, 3-, and 4-year-olds (N = 90) participated in the study. The results indicated that 4-year-olds used significantly more deceptive strategies than 2- and 3-year-olds in pretend play and in sociodramatic play. There was no difference between 2- and 3-year-olds in the use of deceptive strategies; they used significantly fewer strategies in the bad roles than in the good roles. No significant differences were found in the 3 age groups' performances in the good-character tasks. The reality-masking hypothesis (P. Mitchell, 1994) accounts for the differences in performances on that task; thus, children younger than 4 years old do seem to have a theory of mind.     

Instruction-based response activation depends on task preparation

An increasing number of studies have demonstrated that a response in one task can be activated automatically on the basis merely of instructed stimulus–response (S–R) mappings belonging to another task. Such instruction-based response activations are considered to be evidence for the formation of S–R associations on the basis of the S–R mappings for an upcoming, but not yet executed, task. A crucial but somewhat neglected assumption is that instructed S–R associations are formed only under conditions that impose a sufficient degree of task preparation. Accordingly, in the present study we investigated the relation between task preparation and the instruction-based task-rule congruency effect, which is an index of response activation on the basis of instructions. The results from two experiments demonstrated that merely instructed S–R mappings of a particular task only elicit instruction-based response activations when that task is prepared for to a sufficient degree. Implications are discussed for the representation of instructed S–R mappings in working memory.     

Discrimination reversal conditioning of an eyeblink response is impaired by NMDA receptor blockade

In the present study we examined the effects of the specific NMDA receptor antagonist CPP on discrimination reversal learning in rabbits. We report two primary findings. First, the institution of NMDA receptor blockade had no effect on a learned discrimination. Second, after stimulus reversal, CPP treatment impaired acquisition of the discrimination reversal. This impairment manifested itself early in training as a retardation in acquisition of a CR to the new CS+ and late in training as an inability to suppress responsiveness to the new CS-. Given the comparability of the present results with previously published results for phenytoin-treated rabbits, we suggest that the effects of phenytoin on learning in this paradigm is at least in part mediated by its effects on NMDA receptors. We further suggest that these findings emphasize the need to better define the role of NMDA receptor activation and hippocampally-mediated circuits in a variety of associative learning paradigms.     

Theory of mind and executive function: working-memory capacity and inhibitory control as predictors of false-belief task performance

This study of the relationship between theory of mind and executive function examined whether on the false-belief task age differences between 3 and 5 ears of age are related to development of working-memory capacity and inhibitory processes. 72 children completed tasks measuring false belief, working memory, and inhibition. Significant age effects were observed for false-belief and working-memory performance, as well as for the false-alarm and perseveration measures of inhibition. A simultaneous multiple linear regression specified the contribution of age, inhibition, and working memory to the prediction of false-belief performance. This model was significant, explaining a total of 36% of the variance. To examine the independent contributions of the working-memory and inhibition variables, after controlling for age, two hierarchical multiple linear regressions were conducted. These multiple regression analyses indicate that working memory and inhibition make small, overlapping contributions to false-belief performance after accounting for age, but that working memory, as measured in this study, is a somewhat better predictor of false-belief understanding than is inhibition.     

On spatial response code activation in a Simon task

The Simon effect refers to the performance advantage for trials where the task-irrelevant location of a target spatially corresponds with the location of the response. It is thought that the irrelevant spatial code of the target facilitates responding by automatically pre-activating the spatially corresponding response code. This spatial code is thought to passively decay shortly after its activation. In this investigation, the response was selected according to the identity of a central cue. The selected response was executed or withheld depending the identity (Experiment 1) or the presence (Experiment 2) of the target. Varying the stimulus-onset asynchrony (SOA), between the central response cue and the peripheral target, allowed for a time-course analysis of the Simon effect. The results of two experiments provided no indication that the activation level of the irrelevant spatial code decayed while the relevant response was prepared. Although reaction times increased as the SOA decreased, the Simon effect was additive with SOA, suggesting that the automatic activation of the task-irrelevant spatial code was delayed until the task-relevant response code was mostly prepared, perhaps due to the capacity limitations of response selection.     

The effects of dialogue-based task allocation on system performance in a computer-aided air traffic control task

The present study investigated dialogue-based human-computer task allocation. Five levels of allocation mode, four command strategies and a control condition, were examined in a high-task-load situation using a Latin square design. Five male participants acted as controllers in a simplified representation of an air traffic control system, sharing their task with a computer controller. Performance measures were metered on-line, and subjective ratings were recorded between trials. There were significant differences among the groups in the percentage of planes landed by the human-computer system, the total number of commands executed, and the number of allocation commands used. Other variables suggested for further study include comparisons of input mode, dialogue-initiation style, and degraded performance levels of the computer controller.     

More evidence for a relational shift in the development of analogy: Children's performance on a causal-mapping task

Gentner (1988) has proposed a relational shift whereby children interpret analogy and metaphor first in terms of object similarity and then in terms of relational similarity. Goswami (1996) argues against the relational shift hypothesis, citing as evidence a study performed by Goswami and Brown (1989) in which 3-, 4-, and 6-year-old children were able to correctly complete pictorial A:B::C:? analogies based on familiar causal relations, and, contrary to the predictions of the relational shift hypothesis, made very few object-similarity errors despite the presence of an object-similarity choice. In the present experiment we obtained similarity ratings of Goswami and Brown's stimuli and found that the materials did not contain a true object similarity choice and therefore that study was not an adequate test of the relational shift hypothesis. After appropriate modifications to their methodology, we found that 4- and 5-year-old children's performance was consistent with the relational shift hypothesis: First, object-similarity errors were highly frequent initially and decreased with age; second, the rate of relational (correct) responding increased with age; and third, performance on the analogues was positively related to children's knowledge about the participating causal relations. We conclude by proposing an explanation for the relational shift based on an alignment view of similarity comparison and, further, suggest a new role for object similarity in children's analogical development.     

Private speech on an executive task: relations with task difficulty and task performance

Measures of private speech and task performance were obtained for a sample of 46 5- and 6-year-olds engaged on a mechanical version of the Tower of London (ToL) task. Two different sets of four puzzles of increasing difficulty were attempted on two occasions. In line with Vygotskian predictions, there was a quadratic relation between private speech and task difficulty, but no evidence of a shift towards self-regulatory sub-types of private speech with increasing task difficulty. Levels of self-regulatory private speech were significantly related to concurrent, but not subsequent, task performance. We discuss the significance of these findings for the Vygotskian view that private speech has an adaptive function in the self-regulation of behaviour.     

Human performance on an analogue of an interval bisection task

Two experiments used normal adult human subjects in an analogue of a time interval bisection task frequently used with animals. All presented durations were defined by the time between two very brief clicks, and all durations were less than 1 sec, to avoid complications arising from chronometric counting. In Experiment 1 different groups of subjects received standard durations of either 0.2 and 0.8 or 0.1 and 0.9 sec and then classified a range of durations including these values in terms of their similarity to the standard short (0.2- or 0.1-sec) and long (0.8- or 0.9-sec) durations. The bisection point (defined as the duration classified as "long" on 50% of trials) was located at 0.43 sec in the 0.2-0.8 group, and at 0.46 sec in the 0.1-0.9 group. Experiment 2 replicated Experiment 1 using a within-subject procedure. The bisection point of both 0.2- and 0.8 sec and 0.1- and 0.9-sec durations was found to be 0.44 sec. Both experiments thus found the bisection point to be located at a duration just lower than the arithmetic mean of the standard short and long durations, rather than at the geometric mean, as in animal experiments. Some other performance measures, such as difference limen, and Weber ratio, were, however, of similar values to those found in bisection tasks with animals. A theoretical model assuming that humans bisect by taking the difference between a presented duration and the short and long standards, as well as having a bias to respond "long", fitted the data well. The model incorporated scalar representations of standard durations and thus illustrated a way in which the obtained results, although different from those found with animal subjects, could be reconciled with scalar timing theory.     

Knowledge is not everything: analysis of children's performance on a haptic comparison task

The relative effects of developmental level and domain-specific knowledge on children's ability to identify and make similarity decisions about object concepts based only on haptic (touch) information were investigated. Children aged 4-9 years with varying levels of dinosaur knowledge completed a cross-comparison task in which they haptically explored pairs of familiar (dinosaur) and unfamiliar (sea creature) models that varied in terms of their degree of differentiability. Older children explored models more exhaustively, found more differentiating features and consequently made fewer errors than younger children did. High knowledge enabled children to identify models correctly, but was also associated with the use of a hypothesis testing strategy, which led children to make greater numbers of "miss" errors on the cross-comparison task. Performance in the control domain illustrated that the hypothesis testing strategy was specific to the high knowledge domain. Potential explanations for the role of knowledge and development in haptic exploration are considered.     

Development of unimanual versus bimanual task performance in an isometric task

Sixty-three children between 5 and 12 years of age and 15 adults performed a unimanual and a bimanual isometric force task. The performance of the preferred hand in the unimanual task was compared to the performance of the preferred hand in the bimanual task. It was hypothesized that in the bimanual task the absolute error will be higher, there will be more irregularity and the participants will need more time due to the additional effort from the central nervous system, especially with respect to the communication between the hemispheres. Furthermore, in younger children bimanual force variability was expected to be higher due to developmental aspects concerning callosal maturation and attention. It was found that with respect to force generation the preferred hand was not affected by bilateral isometric force generation, but with respect to force regulation it was. The coefficient of variation (CV) of the force was 34% larger in the bimanual task as compared to the unimanual task. For the time to target force, the increase was 28%. With repetition of the trials the CV decreased in the bimanual task, but only in the youngest age group. During development there was no change in absolute error, yet there was a major reduction in force variability in the bimanual task. It is suggested that improvement in interhemispheric communication and in the ability to focus attention plays a role in the decrease in variability with age.     

Aging and performance on an everyday-based visual search task

Research on aging and visual search often requires older people to search computer screens for target letters or numbers. The aim of this experiment was to investigate age-related differences using an everyday-based visual search task in a large participant sample (n=261) aged 20-88 years. Our results show that: (1) old-old adults have more difficulty with triple conjunction searches with one highly distinctive feature compared to young-old and younger adults; (2) age-related declines in conjunction searches emerge in middle age then progress throughout older age; (3) age-related declines are evident in feature searches on target absent trials, as older people seem to exhaustively and serially search the whole display to determine a target's absence. Together, these findings suggest that declines emerge in middle age then progress throughout older age in feature integration, guided search, perceptual grouping and/or spreading suppression processes. Discussed are implications for enhancing everyday functioning throughout adulthood.     

Children's understanding of directed motion events in an imitation choice task

We investigated children’s understanding of directed motion events using an imitation choice paradigm. A total of 34 children (mean age 33 months) watched a model act out an event containing a manner of motion (hopping or sliding), a motion path (up or down a ramp), and a goal (in or on a bowl). On the children’s apparatus, the locations of the goal objects were different from the model so that the children needed to choose whether to imitate the path or the goal of the model’s event. Children’s choice of which component to imitate, therefore, reflects how they prioritize these event components. Most children showed no bias to imitate the goal of the event and, instead, preferred to imitate the model’s path at the expense of the model’s goal. However, children who spontaneously played with the goal objects during a free play session showed a diminished path preference, choosing to imitate path and goal components equally often. We suggest that children’s prioritization of information within an event depends on how that information is structured within the event itself.     

Comparing performance by parents and offspring on a rapid tapping task

The purpose of this study was to identify the relationships between 42 parents' and their offsprings' performance on a rapid tapping task. It was expected that genetic predispositions would gradually limit children's performance on a tapping task as they matured chronologically. Four different age groups of children and their parents performed the tapping task on different sizes of boards. Repeated-measures analysis of variance indicated that, while parents' mean performance was generally higher than that of their children (F = 32.89, p < .001), the difference was affected by the children's age, which hand was used, and the board size. Spearman rank correlation scores between parents' and children's overall performances gradually increased across age groups (p = -.29, -.10, .47, and .40, respectively, from younger to older age groups). This finding suggests that the potential of youngsters' future performance may be predicted with greater certainty by observing their parents' present performance. This may improve the predictive power of planned programs.     

The effect of response contingencies on scale model task performance by chimpanzees (Pan troglodytes)

The effects of modified procedures on chimpanzees' (Pan troglodytes) performance in a scale model comprehension task were examined. Seven chimpanzees that previously participated in a task in which they searched an enclosure for a hidden item after watching an experimenter hide a miniature item in the analogous location in a scale model were retested under procedures incorporating response costs. In Experiment 1, chimpanzees were trained under procedures that rewarded only item retrievals occurring on the 1st search attempt. During test trials, 6 chimpanzees performed above chance, including 4 that were previously unsuccessful under the original procedures (V. A. Kuhlmeier, S. T. Boysen, & K. L. Mukobi, 1999). Experiment 2 compared performance under the new and original procedures. Results indicated that for some chimpanzees, performance depended on procedures that decreased the use of competing search strategies and encouraged strategies based on information from the scale model.     

Effects of delay of prospective memory cues in an ongoing task on prospective memory task performance

To address the mixed results reported in previous studies, the present experiments examined forgetting in prospective memory (PM) by manipulating the delay between the PM instructions and cue presentation in event-based PM tasks. PM performance was measured for delays of 2–20 min in Experiment 1 and for delays of approximately 1–10 min in Experiment 2. Experiment 2 included both focal and nonfocal PM tasks, and speed on the ongoing task was measured to examine evidence for monitoring processes across the delays tested. The results suggest that nonfocal PM performance follows a nonlinear forgetting function (i.e., rapid decline for shorter delays and slower decline for longer delays) when tested over delays from 1 to 20 min. No effect of delay was seen for the focal task tested in Experiment 2 from 1 to 10 min. In Experiment 2, ongoing-task costs were also found for the first delay but not for longer delays, suggesting that monitoring was significantly reduced between 1 and 2.5 min of the ongoing-task trials.     

Time-pressure effects on performance in a base-rate task

Researchers assume that time pressure impairs performance in decision tasks by invoking heuristic processes. In the present study, the authors inquired (a) whether it was possible in some cases for time pressure to improve performance or to alter it without impairing it, and (b) whether the heuristic invoked by base-rate neglect under direct experience can be identified. They used a probability-learning design in 2 experiments, and they measured the choice proportions after each of 2 possible cues in each experiment. In 1 comparison, time pressure increased predictions of the more likely outcome, which improved performance. In 2 comparisons, time pressure changed the choice proportions without affecting performance. In a 4th comparison, time pressure hindered performance. The choice proportions were consistent with heuristic processing that is based on cue matching rather than on cue accuracy, base rates, or posterior probabilities.