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.     

Visual and acoustic confusability a visual search task

Visual and acoustic confusability between a target item and background items was varied in a visual search task. Visual confusability was a highly significant source of difficulty while acoustic confusability had no effect. The results do not seem to be interpretable within a theory which assumes compulsory auditory encoding of visual information.     

Visual and acoustic confusability a visual search task

Visual and acoustic confusability between a target item and background items was varied in a visual search task. Visual confusability was a highly significant source of difficulty while acoustic confusability had no effect. The results do not seem to be interpretable within a theory which assumes compulsory auditory encoding of visual information.     

Visual search in a forced-choice paradigm

The processing of visual information was investigated in the context of two visual search tasks. The first was a forced-choice task in which one of two alternative letters appeared in a visual display of from one to five letters. The second task included trials on which neither of the two alternatives was present in the display. Search rates were estimated from the slopes of best linear fits to response latencies plotted as a function of the number of items in the visual display. These rates were found to be much slower than those estimated in yes-no search tasks. This result was interpreted as indicating that the processes underlying visual search in yes-no and forced-choice tasks are not the same.     

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.     

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.     

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.     

You detect while I search: examining visual search efficiency in a joint search task

Numerous factors impact attentional allocation, with behaviour being strongly influenced by the interaction between individual intent and our visual environment. Traditionally, visual search efficiency has been studied under solo search conditions. Here, we propose a novel joint search paradigm where one individual controls the visual input available to another individual via a gaze contingent window (e.g., Participant 1 controls the window with their eye movements and Participant 2 – in an adjoining room – sees only stimuli that Participant 1 is fixating and responds to the target accordingly). Pairs of participants completed three blocks of a detection task that required them to: (1) search and detect the target individually, (2) search the display while their partner performed the detection task, or (3) detect while their partner searched. Search was most accurate when the person detecting was doing so for the second time while the person controlling the visual input was doing so for the first time, even when compared to participants with advanced solo or joint task experience (Experiments 2 and 3). Through surrendering control of one’s search strategy, we posit that there is a benefit of a reduced working memory load for the detector resulting in more accurate search. This paradigm creates a counterintuitive speed/accuracy trade-off which combines the heightened ability that comes from task experience (discrimination task) with the slower performance times associated with a novel task (the initial search) to create a potentially more efficient method of visual search.     

Control of fixation duration in a simple search task

To obtain insight into the control of fixation duration during visual search, we had 4 subjects perform simple search tasks in which we systematically varied the discriminability of the target. The experiment was carried out under two conditions. Under the first condition (blocked), the discriminability of the target was kept constant during a session. Under the second condition (mixed), the discriminability of the target varied per trial. Under the blocked condition, fixation duration increased with decreasing discriminability. For 2 subjects, we found much shorter fixation durations in difficult trials with the mixed condition than in difficult trials with the blocked condition. Overall, the subjects fixated the target, continued to search, and then went back to the target in 5%–55% of the correct trials. In these trials, the result of the analysis of the foveal target was not used for preparing the next saccade. The results support a preprogramming model of the control of fixation duration. In a simple search task, control of fixation duration appears to be indirect.     

Object boundaries influence toddlers' performance in a search task

Previous research has shown that young children have difficulty searching for a hidden object whose location depends on the position of a partly visible physical barrier. Across four experiments, we tested whether children's search errors are affected by two variables that influence adults' object-directed attention: object boundaries and proximity relations. Toddlers searched for a car that rolled down a ramp behind an occluding panel and stopped on contact with a barrier. The car's location on each trial depended on the placement of the barrier behind one of two doors in the panel. In Experiment 1, when a part of the car (a pompom on an antenna) was visible at the same distance from the object as the barrier wall in past research, search performance was above chance but below ceiling. In Experiments 2 and 3, when the visible part was close to the hidden body of the car and could be seen through one of two windows in the doors of the occluding panel, performance was near ceiling. In Experiment 4, when only the barrier was visible through one of the same windows, performance was at chance. Toddlers' search for a hidden object therefore is affected by the proximity of a visible part of the object, though not by the proximity of a separate visible landmark. These findings suggest a parallel between the object representations of young children and those of adults, whose attention is directed to objects and spreads in a gradient-like fashion within an object.     

Visual exploration and hazard search strategies in a simulated road crossing task among primary and secondary school students in Tanzania

Pedestrians, cyclists, motorcyclists, and other vulnerable road users represent more than half of all road fatalities globally. In Tanzania, pedestrians account for a significant proportion of the death toll, accounting for 30% of all traffic fatalities (WHO, 2018) and a 2016 study conducted in Dar Es Salaam found that 87% of school-aged children walk to school (Draisin, 2016), highlighting that school-aged children are exposed to a high level of risk.The present work reports the results of a study conducted in primary and secondary schools in the Arusha Region of Tanzania which investigates the students’ road crossing mental representation, as well as their level of hazard perception awareness, through their declared gaze behaviour. The students were asked to identify and tell the areas where hazards could come from within three road crossing scenarios, thus exploring the mental representation of the visual exploration strategies applied by children and teenagers when crossing the road. Results showed the tendency to apply the “compliant gaze behaviour” pattern in a flexible manner and to integrate it with the exploration of other areas in the visual field, particularly by the senior students. Practical implications for planning effective pedestrian road safety training programs are discussed.     

Visual search enhances subsequent mnemonic search

We examined how the performance of a visual search task while studying a list of to-be-remembered words affects subsequent memory for those words by humans. Previous research had suggested that episodic context encoding is facilitated when the study phase of a memory experiment requires, or otherwise encourages, a visual search for the to-be-remembered stimuli, and theta-band oscillations are more robust when animals are searching their environment. Moreover, hippocampal theta oscillations are positively correlated with learning in animals. We assumed that a visual search task performed during the encoding of words for a subsequent memory test would induce an exploratory state that would mimic the one that is induced in animals when performing exploratory activities in their environment, and that the encoding of episodic traces would be improved as a result. The results of several experiments indicated that the performance of the search task improved free recall, but the results did not extend to yes–no or forced choice recognition memory testing. We propose that visual search tasks enhance the encoding of episodic context information but do not enhance the encoding of to-be-remembered words.     

An informational analysis of a visual search task

An earlier paper examined a visual-search task that required a S to locate a two-digit symbol from an array of digits. The results were not subjected to a detailed theoretical analysis. The present paper suggests an information-theory analysis of the data and shows that all of the data can be reduced to a consistent format. It is also argued that such an analysis may prove fruitful in the investigation of search strategies.