Evaluating the two-component inspection model in a simplified luggage search task

Visual inspection of X-ray images of luggage is a time-pressured task that typically shows large initial training effects, but there exists a paucity of models capable of evaluating performance and speed concurrently. In the present study, visual inspection ability during learning was modeled using Drury’s two-component inspection model (TCM; Drury, 1975) in a laboratory experiment involving 12 younger (mean age = 20.8 years) and 12 older (mean age = 60.0 years) naive participants undertaking a simplified luggage search task. Model fits and assumptions were found to be reliable and accurately reflected improvement with training for decision time, although neither search nor decision components of the model individually showed a significant effect of age. The decision component of the model showed larger improvement with training than did the search component, and stopping-time policy accurately reflected the improvements found between ages and within training levels. The TCM is a useful supplement to detection theory when speed of performance is a factor.     

Young children's spontaneous use of geometry in maps

Two experiments tested whether 4-year-old children extract and use geometric information in simple maps without task instruction or feedback. Children saw maps depicting an arrangement of three containers and were asked to place an object into a container designated on the map. In Experiment 1, one of the three locations on the map and the array was distinct and therefore served as a landmark; in Experiment 2, only angle, distance and sense information specified the target container. Children in both experiments used information for distance and angle, but not sense, showing signature error patterns found in adults. Children thus show early, spontaneously developing abilities to detect geometric correspondences between three-dimensional layouts and two-dimensional maps, and they use these correspondences to guide navigation. These findings begin to chart the nature and limits of the use of core geometry in a uniquely human, symbolic task.     

Conflicting cues in a dynamic search task are reflected in children's eye movements and search errors

Three-year-olds were given a search task with conflicting cues about the target's location. A ball rolled behind a transparent screen and stopped behind one of four opaque doors mounted into the screen. A wall that protruded above one door provided a visible cue of blockage in the ball's path, while the transparent screen allowed visual tracking of the ball's progress to its last disappearance. On some trials these cues agreed and on others they conflicted. One group saw the ball appear to pass through the wall, violating its solidity, and another group saw the ball stop early, behind a door before the visual wall. Children's eye movements were recorded with an Applied Science Laboratories eye tracker during these real object events. On congruent trials, children tended to track the ball to the visible barrier and select that door. During conflict trials, children's eye movements and reaching errors reflected the type of conflict they experienced. Our data support Scholl and Leslie's (1999) hypotheses that spatio-temporal and contact mechanical knowledge are based on two separate, distinct mechanisms.     

Evidence for two kinds of low-typical instances in a categorization task

Three experiments examined the relationship between instance typicality and reaction time (RT) in a semantic categorization task. In all three experiments, first the instance was presented, and then the category. High-typicality high-imagery instances (e.g., robin) and lowtypicality low-imagery instances (e.g., grackle) were categorized faster than low-typicality highimagery instances (e.g., penguin). Instructing subjects to generate images of the instances had no influence on the pattern of results. The difference in categorization RT for lowimagery low-typicality instances vs. high-imagery high-typicality instances suggests that these instances may be represented differently in memory.     

Young children's knowledge of their memory span: effects of task and experience

This study investigated the hypothesis that young children have knowledge about their memory that they may be unable to articulate, but are able to reflect on and use in problem-solving. Forty-eight kindergarteners made one of two types of judgments about their memory span for words. Half of the children made prospective verbal predictions about the number of words they thought they could recall from a list of 10. The other half made concurrent, nonverbal predictions by listening to words on a tape and manually stopping the tape when they heard as many words as they thought they could recall. Children's actual recall for words was then assessed. All children participated in multiple trials to assess the effect of task experience on their predictions. Analyses revealed that predictions made in the concurrent task were significantly more accurate than those made in the prospective task. All children lowered their predictions across trials, although only in the concurrent task were children's final-trial predictions not significantly greater than their actual recall. No meaningful effects or interactions were associated with actual recall scores. These results revealed that young children manifested greater memory knowledge when this knowledge was assessed through their concurrent problem-solving behavior rather than through their prospective verbal predictions.     

Young children's organizational strategies on a same-different task: A microgenetic study and a training study.

This study was designed to explore young children's strategy development using a new kind of "same-different" task that minimized memory demands. Four-year-old children were asked to judge whether 2 sets of 7 toys were the same or different. Sets were identical or differed by one toy, with one set presented on a table and the other in a linen bag. Children's spontaneous behavior was highly strategic, and over trials it developed differently for "same" and "different" trials. Most children who did not spontaneously use the most effective strategy, that is, matching, could be trained to do so and were able to transfer this strategy to new materials. Results concerning production and utilization deficiencies are discussed in relation to task characteristics, trial type (same or different), and findings from prior research.     

Visual search and foraging compared in a large-scale search task

It has been argued that visual search is a valid model for human foraging. However, the two tasks differ greatly in terms of the coding of space and the effort required to search. Here we describe a direct comparison between visually guided searches (as studied in visual search tasks) and foraging that is not based upon a visually distinct target, within the same context. The experiment was conducted in a novel apparatus, where search locations were indicated by an array of lights embedded in the floor. In visually guided conditions participants searched for a target defined by the presence of a feature (red target amongst green distractors) or the absence of a feature (green target amongst red and green distractors). Despite the expanded search scale and the different response requirements, these conditions followed the pattern found in conventional visual search paradigms: feature-present search latencies were not linearly related to display size, whereas feature-absent searches were longer as the number of distractors increased. In a non-visually guided foraging condition, participants searched for a target that was only visible once the switch was activated. This resulted in far longer latencies that rose markedly with display size. Compared to eye-movements in previous visual search studies, there were few revisit errors to previously inspected locations in this condition. This demonstrates the important distinction between visually guided and non-visually guided foraging processes, and shows that the visual search paradigm is an equivocal model for general search in any context. We suggest a comprehensive model of human spatial search behaviour needs to include search at a small and large scale as well as visually guided and non-visually guided search.     

Implicit sequence learning in a search task

This study investigated the effects of selection demands on implicit sequence learning. Participants in a search condition looked for a target among seven distractors and responded on the target identity. The responses followed a deterministic sequence, and sequence learning was compared to that found in two control conditions in which the targets were presented alone, either at a central location or over a series of unpredictable locations. Sequence learning was obtained in all conditions, and it was equivalent for the two variable location conditions, regardless of the perceptual demands. Larger effects of learning were observed in the central location, both on the indirect measures and on the measures taken from a cued-generation task. The expression of learning decreased selectively in this condition when the sequence validity was reduced over a test block. These results are consistent with the claims that implicit and explicit learning are mixed in this central condition and that implicit learning is not affected by selection difficulty.     

Implicit sequence learning in a search task

This study investigated the effects of selection demands on implicit sequence learning. Participants in a search condition looked for a target among seven distractors and responded on the target identity. The responses followed a deterministic sequence, and sequence learning was compared to that found in two control conditions in which the targets were presented alone, either at a central location or over a series of unpredictable locations. Sequence learning was obtained in all conditions, and it was equivalent for the two variable location conditions, regardless of the perceptual demands. Larger effects of learning were observed in the central location, both on the indirect measures and on the measures taken from a cued-generation task. The expression of learning decreased selectively in this condition when the sequence validity was reduced over a test block. These results are consistent with the claims that implicit and explicit learning are mixed in this central condition and that implicit learning is not affected by selection difficulty.     

Toddlers' use of cues in a search task

Search for a ball that has undergone hidden motion rapidly improves during the second year of life (Dev. Psychol., 2000; 36 :394–401). In three experiments we investigated whether the poor performance of younger toddlers was due to attentional failure by highlighting the major cue for the hidden object. We observed only slight improvement in search behaviour. We performed two other experiments that tested the depth of understanding of 3‐year‐olds in this task and found that their performance was robust to changes in the apparatus and experimental procedures. Overall, the results point to a rapidly developing ability in the second year of life to either reason about space or select the correct motor response in search tasks. Copyright © 2008 John Wiley & Sons, Ltd.     

Young children's change in strategies of size comparison: Effects of task repetition and strategy evaluation

This study examined how young children change their strategies for size comparison. Twenty-two 5 and 6-year-old children were asked to compare the sizes of geometric figures and their strategies were observed once a week over three weeks. Half of the children were also asked to evaluate presented strategies for comparing geometric figures. It was found that over three weeks not only children who evaluated the strategies but also children who did not increased correct responses, the strategy of placing one figure on another, and the strategy of adjusting two figures by two dimensions. Although more children became aware of the effectiveness of those strategies, there was no relationship between the evaluation and use of strategies.     

The influence of memory for prior instances on performance in a conflict detection task

In 3 experiments, the authors examined the role of memory for prior instances for making relative judgments in conflict detection. Participants saw pairs of aircraft either repeatedly conflict with each other or pass safely before being tested on new aircraft pairs, which varied in similarity to the training pairs. Performance was influenced by the similarity between aircraft pairs. Detection time was faster when a conflict pair resembled a pair that had repeatedly conflicted. Detection time was slower, and participants missed conflicts, when a conflict pair resembled a pair that had repeatedly passed safely. The findings identify aircraft features that are used as inputs into the memory decision process and provide an indication of the processes involved in the use of memory for prior instances to make relative judgments.     

Production of negative transfer in a problem-solving task

72 students solved two problems using a source problem designed to inhibit performance on the target problem relative to baseline performance when the target problem was solved alone. Both source and target problems shared surface similarity but were structurally dissimilar. Negative transfer was found for three different source and target combinations. The decreased performance below baseline for three of the source-target programs provides a reliable context to demonstrate negative transfer and facilitate continued investigation of this phenomenon.     

Explanation and verbalization in a computer-assisted search task

Three experiments examine the effects of two different forms of explanation on assisted performance on a complex search task. The task involves determining which of a set of factories is responsible for polluting a river by testing the river for the presence or absence of various pollutants. All subjects receive computer suggestions as to which pollutants they should test for. In addition, some subjects receive an explanation of the principle according to which the advice program works. Two forms of explanation are compared. Experiment 1 shows that subjects who are allowed to ask “why” each computer recommendation is made perform significantly better than those who are provided with a block text of explanation at the start of each trial. Experiment 2 shows that the latter type of explanation is not completely ineffective, however. Subjects who are required to verbalize following the single explanation perform significantly better than do subjects who are required to verbalize but who have not received any form of explanation. Finally, Experiment 3 shows that subjects who receive the multiple “why” explanations or the explanation/verbalization combination maintain a superior performance level on subsequent unaided trials.     

Global statistical learning in a visual search task

Locating a target in a visual search task is facilitated when the target location is repeated on successive trials. Global statistical properties also influence visual search, but have often been confounded with local regularities (i.e., target location repetition). In two experiments, target locations were not repeated for four successive trials, but with a target location bias (i.e., the target appeared on one half of the display twice as often as the other). Participants quickly learned to make more first saccades to the side more likely to contain the target. With item-by-item search first saccades to the target were at chance. With a distributed search strategy first saccades to a target located on the biased side increased above chance. The results confirm that visual search behavior is sensitive to simple global statistics in the absence of trial-to-trial target location repetitions.