Michael J. Stroud

Search for two categories of target produces fewer fixations to target-color items.

Searching simultaneously for metal threats (guns and knives) and improvised explosive devices (IEDs) in X-ray images is less effective than 2 independent single-target searches, 1 for metal threats and 1 for IEDs. The goals of this study were to (a) replicate this dual-target cost for categorical targets and to determine whether the cost remains when X-ray images overlap, (b) determine the role of attentional guidance in this dual-target cost by measuring eye movements, and (c) determine the effect of practice on guidance. Untrained participants conducted 5,376 trials of visual search of X-ray images, each specializing in single-target search for metal threats, single-target search for IEDs, or dual-target search for both. In dual-target search, only 1 target (metal threat or IED) at most appeared on any 1 trial. Eye movements, response time, and accuracy were compared across single-target and dual-target searches. Results showed a dual-target cost in response time, accuracy, and guidance, with fewer fixations to target-color objects and disproportionately more to non-target-color objects, compared with single-target search. Such reduction in guidance explains why targets are missed in dual-target search, which was particularly noticeable when objects overlapped. After extensive practice, accuracy, response time, and guidance remained better in single-target search than in dual-target search. The results indicate that, when 2 different target representations are required for search, both representations cannot be maintained as accurately as in separate single-target searches. They suggest that baggage X-ray security screeners should specialize in one type of threat, or be trained to conduct 2 independent searches, 1 for each threat item.

Summoning Prior Knowledge Through Metaphorical Graphics: An Example in Chemistry Instruction

ABSTRACT The present investigation was designed to determine if the learning benefits of metaphors and graphics could be combined into one instructional device—a metaphorical graphic—to aid in the acquisition of difficult concepts of chemistry. The authors further sought to determine if metaphorical graphics could foster greater retention of the basic properties of chemical elements when compared to verbal descriptions of those properties or traditional graphical representations of elements commonly seen as orbital diagrams in chemistry textbooks. The findings revealed that metaphorical graphics helped learners to develop a deeper understanding of the behavior and reactivity, but not physical properties, of the features of fifteen selected chemical elements.

More than just finding color: strategy in global visual search is shaped by learned target probabilities.

In 2 experiments, eye movements were examined during searches in which elements were grouped into four 9-item clusters. The target (a red or blue T) was known in advance, and each cluster contained different numbers of target-color elements. Rather than color composition of a cluster invariantly guiding the order of search though clusters, the use of color was determined by the probability that the target would appear in a cluster of a certain color type: When the target was equally likely to be in any cluster containing the target color, fixations were directed to those clusters approximately equally, but when targets were more likely to appear in clusters with more target-color items, those clusters were likely to be fixated sooner. (The target probabilities guided search without explicit instruction.) Once fixated, the time spent within a cluster depended on the number of target-color elements, consistent with a search of only those elements. Thus, between-cluster search was influenced by global target probabilities signaled by amount of color or color ratios, whereas within-cluster search was directly driven by presence of the target color.

Casual video games as training tools for attentional processes in everyday life

Three experiments examined the attentional components of the popular match-3 casual video game, Bejeweled Blitz (BJB). Attentionally demanding, BJB is highly popular among adults, particularly those in middle and later adulthood. In experiment 1, 54 older adults (Mage = 70.57) and 33 younger adults (Mage = 19.82) played 20 rounds of BJB, and completed online tasks measuring reaction time, simple visual search, and conjunction visual search. Prior experience significantly predicted BJB scores for younger adults, but for older adults, both prior experience and simple visual search task scores predicted BJB performance. Experiment 2 tested whether BJB practice alone would result in a carryover benefit to a visual search task in a sample of 58 young adults (Mage = 19.57) who completed 0, 10, or 30 rounds of BJB followed by a BJB-like visual search task with targets present or absent. Reaction times were significantly faster for participants who completed 30 but not 10 rounds of BJB compared with the search task only. This benefit was evident when targets were both present and absent, suggesting that playing BJB improves not only target detection, but also the ability to quit search effectively. Experiment 3 tested whether the attentional benefit in experiment 2 would apply to non-BJB stimuli. The results revealed a similar numerical but not significant trend. Taken together, the findings suggest there are benefits of casual video game playing to attention and relevant everyday skills, and that these games may have potential value as training tools.

Dual Target Search is Neither Purely Simultaneous nor Purely Successive.

Previous research shows that visual search for two different targets is less efficient than search for a single target. Stroud, Menneer, Cave, and Donnelly concluded that two target colours are represented separately based on modelling the fixation patterns. Although those analyses provide evidence for two separate target representations, they do not show whether participants search simultaneously for both targets, or first search for one target and then the other. Some studies suggest that multiple target representations are simultaneously active, while others indicate that search can be voluntarily simultaneous, or switching, or a mixture of both. Stroud et al.’s participants were not explicitly instructed to use any particular strategy. These data were revisited to determine which strategy was employed. Each fixated item was categorised according to whether its colour was more similar to one target or the other. Once an item similar to one target is fixated, the next fixated item is more likely to be similar to that target than the other, showing that at a given moment during search, one target is generally favoured. However, the search for one target is not completed before search for the other begins. Instead, there are often short runs of one or two fixations to distractors similar to one target, with each run followed by a switch to the other target. Thus, the results suggest that one target is more highly weighted than the other at any given time, but not to the extent that search is purely successive.

Online and Classroom Simulations: Does Video Use Inspire Interest, Comprehensibility, or Achieve Learning Outcomes?

This study examined whether a video illustration of a complex phenomenon promoted learner interest, perceived comprehensibility, and better learning in online- and classroom-based contexts. In the first study, undergraduate participants (N = 101) viewed learning materials which contained a video only, a video and textual explanation, or a textual explanation alone. Participants rated the interestingness and comprehensibility of the instructional materials and completed a learning outcomes test. The second study (N = 56) included the same learning materials in a classroom context. The video presentation of the material did not improve learning outcomes, in either context. Participants in the computer-delivered context who only viewed the text learned the material better than those who had viewed the video. In the classroom-delivered context, the video neither helped nor hurt the learning outcomes, but it also did not significantly boost learners’ interest. Taken together, findings from the present study indicate potential limited utility of including video material within these instructional contexts.

Modeling search guidance: Three parameters for characterizing performance in different types of visual search.

The accuracy of search guidance is reflected in the probability of fixating distractors within a search display as a function of their similarity to the target (e.g., Stroud et al. , JEP: HPP, 2012). Strong search guidance produces high fixation rates to distractors that match the target on a given dimension (e.g., color), and low fixation rates to distractors that do not match the target. When guidance is absent, fixation rates are equal across all distractors, regardless of similarity to target. We modeled fixation rates across different levels of target similarity using a sigmoid function. Three parameters are necessary and sufficient to fit the function across a range of color-search tasks: single-target search, dual-target search, search plus a working-memory task, and search plus shape discrimination (modeled data: Stroud et al., ACP, 2011; Stroud et al., VSS, 2011; Stroud et al. , JEP: HPP, 2012; Menneer et al., BPS, 2014). These parameters are as follows. (1) Unguided fixation rate (u): Even in guided search, participants exhibit a baseline fixation rate to distractors that are maximally different to the target. u defines the ratio of unguided fixations to guided fixations. (2) Selectivity (s): Participants with high selectivity (e.g., for target-similar colors) exhibit a guidance curve that drops off steeply for distractors less similar to the target, while low selectivity produces a shallow drop-off. (3) Target region (t): Some tasks produce high fixation rates to the target color only, but others produce high fixations rates to a range of colors similar to the target color. t allows adjustment of the region in color space that receives high fixation rates, and determines the level of dissimilarity at which the fixation rate begins to drop off steeply. The estimates for these three parameters demonstrate how guidance changes across different types of search. Meeting abstract presented at VSS 2015.

A Color in Working Memory Does Not Become a Search Target, but it Does Interfere with Color Search

Eyelink II Eyetracker: 250 Hz; Pupil and CR A Color in Working Memory Does Not Become a Search Target, but it Does Interfere with Color Search Michael J. Stroud1, Elina Kaplan2, Tamaryn Menneer3, Kyle R. Cave2, and Nick Donnelly3 1Department of Psychology, Merrimack College; 2Department of Psychology, University of Massachusetts, Amherst; 3Centre for Visual Cognition, School of Psychology, University of Southampton, UK