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It has been suggested that a common cognitive system is employed in magnitude judgments across multiple modal-ities (Walsh, 2003). To test this theory, we examined whether performance on magnitude judgments of number, surface area,duration, and loudness correlated with each other in both magnitude comparison (e.g., determine which is more), and mag-nitude estimation (e.g., if magnitude 1 value = 100, estimate the value of magnitude 2) tasks. For magnitude comparison,significant correlations were observed between number, surface area, and loudness (but not duration) tasks (percent correctmeasured). Similar results were observed for magnitude estimation (mean absolute percent deviation of value estimates fromcorrect measured). These results are indicative of a common cognitive system for at least some magnitude judgment modalities,and suggest that such a system may play a role not only in more-than/less-than magnitude judgments, but also in the process ofassigning numerical values to magnitudes.

When participants carry out concurrent tasks there can be overlap in action plans. This study shows the effects of action-plan overlap in a multiple-object tracking (MOT) task where participants tracked 1–4 targets while touching any items that changed colour during the item motion phase of tracking trial (either targets or distractors in MOT). We manipulated the way that participants reported MOT targets at the end of the trial. Participants (untimed) either reported targets by touching them with the index finger of their dominant hand (maximal overlap between target report and touching items that changed colour) or typed in letters corresponding to targets with their non-dominant hand (minimal overlap). Target report had no effect on single-task MOT performance. However, when participants had to touch items that changed colour during tracking, MOT was significantly worse when participants reported targets by typing them in rather than touching them and it also took participants longer to touch items that changed colour even though these colour changes preceded target report by 7–8 s. Nonetheless, target-report did not affect the performance discrepancy between the target- and distractor-touch conditions, which suggests performance differences between these two conditions reflect differences in attentional selection rather than action-plan overlap. [ABSTRACT FROM AUTHOR]

Multiple-object tracking involves simultaneously monitoring positions of a number of target items as they move among distractors. Young adults are capable of tracking only 3-5 items at once. In this study we investigated the origin of this limitation by looking for secondary tasks that interfere with tracking. We compared tracking performance (baseline condition), with performance when participants tapped three fingers in a specific order while tracking (sequential tapping) or articulated three syllables in a specific order while tracking (sequential articulation). The articulation task was used to ensure that the interference produced by sequential tapping was more than would be expected by the executive demands of carrying out any two 'attention-demanding' tasks at once. Even though sequential tapping does not require vision or memorizing the positions of external items, it produced significantly more interference than did sequential articulation, as might be expected if tracking and sequential tapping shared a common (limited) resource.

Multiple-object tracking is the ability to attend (keep track of) the positions of multiple larger items as they move among other items. The performance of young and older adults (M = 19 and 73 years old, respectively) was compared in two versions of a tracking task in which participants were required to monitor the positions of 1-4 moving targets in a field of 10 moving items. All participants were capable of tracking more than 1 item at once, but on average older participants tracked around 3 items at once whereas young adults tracked 4. Results suggest that there are age differences in the ability to either track or report positions of moving items. All participants reported positions of 1-4 targets in a field of 10 items with 100% accuracy when items were static.

The gambler's fallacy was examined in terms of grouping processes. The gambler's fallacy is the tendency to erroneously believe that for independent events, recent or repeated instances of an outcome (e.g., a series of 'heads' when flipping a coin) will make that outcome less likely on an upcoming trial. Grouping was manipulated such that a critical trial following a run of heads or tails was grouped together with previous trials (i.e., the last trial of 'Block 1') or was the first trial of another group (the first trial of 'Block 2'). As predicted, the gambler's fallacy was evident when the critical trial was grouped with the previous trials, but not when it was arbitrarily grouped with the next block of trials. Discussion centres on the processes underlying the gambler's fallacy and practical implications of these findings.

'Subitizing,' the process of enumeration when there are fewer than 4 items, is rapid (40-100 ms/item), effortless, and accurate. 'Counting,' the process of enumeration when there are more than 4 items, is slow (250-350 ms/item), effortful, and error-prone. Why is there a difference in the way the small and large numbers of items are enumerated? A theory of enumeration is proposed that emerges from a general theory of vision, yet explains the numeric abilities of preverbal infants, children, and adults. We argue that subitizing exploits a limited-capacity parallel mechanism for item individuation, the FINST mechanism, associated with the multiple target tracking task (Pylyshyn, 1989; Pylyshyn & Storm, 1988). Two kinds of evidence support the claim that subitizing relies on preattentive information, whereas counting requires spatial attention. First, whenever spatial attention is needed to compute a spatial relation (cf. Ullman, 1984) or to perform feature integration (cf. Treisman & Gelade, 1980), subitizing does not occur (Trick & Pylyshyn, 1993a). Second, the position of the attentional focus, as manipulated by cue validity, has a greater effect on counting than subitizing latencies (Trick & Pylyshyn, 1993b).

Subitizing, the enumeration of 1-4 items, is rapid (40-120 ms/item) and accurate. Counting, the enumeration of 5 items or more, is slow (250-350 ms/item) and error-prone. Why are small numbers of items enumerated differently from large numbers of items? It is suggested that subitizing relies on a preattentive mechanism. Ss could subitize heterogeneously sized multicontour items but not concentric multicontour items, which require attentional processing because preattentive gestalt processes misgroup contours from different items to form units. Similarly, Ss could subitize target items among distractors but only if the targets and distractors differed by a feature, a property derived through preattentive analysis. Thus, subitizing must rely on a mechanism that can handle a few items at once, which operates before attention but after preattentive operations of feature detection and grouping.