Underestimating numerosity of items in visual search tasks

Previous research on numerosity judgments addressed attended items, while the present research addresses underestimation for unattended items in visual search tasks. One potential cause of underestimation for unattended items is that estimates of quantity may depend on viewing a large portion of the display within foveal vision. Another theory follows from the occupancy model: estimating quantity of items in greater proximity to one another increases the likelihood of an underestimation error. Three experimental manipulations addressed aspects of underestimation for unattended items: the size of the distracters, the distance of the target from fixation, and whether items were clustered together. Results suggested that the underestimation effect for unattended items was best explained within a Gestalt grouping framework.     

Intentional control of event counting

Event counting depends on simple, well-learned knowledge but is effortful and error-prone. In 6 experiments, the authors examined event-counting performance, testing a model that suggests that counting is controlled by minimal goal representations coordinated with perceptual events by temporal synchrony. In Experiment 1, they examined self-paced counting with or without delays that disrupted participants' preferred pacing. In subsequent experiments, participants counted computer-paced events occurring at rhythmic or varied intervals, reporting or verifying totals. Several results support the model: Participants counted rhythmic events more accurately, made undetected undercount errors when counting rhythmic events, and made false alarms to undercount or overcount probes presented at different times. These results suggest that intentions that guide fluent counting specify parameters deictically rather than semantically and that error monitoring is implicit.     

Effect of pacing and working memory loads on error type patterns in a routine skill

Event counting provides a laboratory paradigm for studying types and causes of error in routine activity. Experiment 1 demonstrated that as more time per event is allowed, counting errors typically are undercounts, then overcounts as the time per event is extended to approximately 3 s. Experiments 2 and 3 examined 2 possible causes of this phenomenon, forgetting and confusions due to overrehearsal of the next number to be used. These findings demonstrate that overcount errors during event counting are reduced by working memory loads, which may result from a lower ability to rehearse the current total. Implications for theoretical accounts of goal representation, control, and error monitoring are discussed.     

Numerosity estimates for attended and unattended items in visual search

The goal of this research was to examine memories created for the number of items during a visual search task. Participants performed a visual search task for a target defined by a single feature (Experiment 1A), by a conjunction of features (Experiment 1B), or by a specific spatial configuration of features (Experiment 1C). On some trials following the search task, subjects were asked to recall the total number of items in the previous display. In all search types, participants underestimated the total number of items, but the severity of the underestimation varied depending on the efficiency of the search. In three follow-up studies (Experiments 2A, 2B, and 2C) using the same visual stimuli, the participants’ only task was to estimate the number of items on each screen. Participants still underestimated the numerosity of the items, although the degree of underestimation was smaller than in the search tasks and did not depend on the type of visual stimuli. In Experiment 3, participants were asked to recall the number of items in a display only once. Subjects still displayed a tendency to underestimate, indicating that the underestimation effects seen in Experiments 1A-1C were not attributable to knowledge of the estimation task. The degree of underestimation depends on the efficiency of the search task, with more severe underestimation in efficient search tasks. This suggests that the lower attentional demands of very efficient searches leads to less encoding of numerosity of the distractor set.     

Effects of information accuracy and volume on decision making

Recent advances in information technology have resulted in increasingly complex work environments. Much of the complexity is due to a deluge of information available across networks (Gleick, 2011) and unknown reliability, which introduces additional uncertainty (Platt & Huettel, 2008). Understanding the performance characteristics of human information processing for optimal decision making under such conditions of data abundance and uncertainty is critical in complex networked information environments, such as military operations. One focus of the United States military is providing troops with the richness of information formally reserved for higher echelons (Bawden & Robinson, 2009). However, this effort risks cognitive overload, where too much information can result in impaired performance. The present study examined human decision making under varying levels of cognitive load and source reliability. Participants determined the reliability of two information sources and decided how to use them to minimize cognitive load and improve performance in a visual search task. Unbeknownst to participants, one source provided highly accurate information and one provided moderately accurate information. Results showed that participants had more trust in the more accurate than the less accurate source, and decision making accuracy decreased as cognitive load increased. When cognitive load was highest, participants were more accurate on trials with the more accurate source. Thus, the more accurate source facilitated better performance, whether through better intel or through participants offloading some of the cognitive load to the reliable source.