The mathematics of multiple object tracking: From proportions correct to number of objects tracked

AbstractThis paper examines the relation between proportions correct responses and the number of items tracked in multiple object tracking (MOT). It analyses two of the principle methods used in MOT. The mark all method, where the participants have to mark all the items, is shown to be equivalent to sampling without replacement. For the probe one method, where participants have to indicate whether a particular item belongs to the target set, formulas are derived as well.The paper shows that it is not possible to determine the tracked number of target items (m) and distractor items (v) from the proportions correct answers when employing only one of these two methods. A combination of the mark all and probe one methods does not yield a unique relation between the proportions correct and m and v either, because of the interchangeability between tracking targets and tracking distractors

Medium versus difficult visual search: How a quantitative change in the functional visual field leads to a qualitative difference in performance

The dominant theories of visual search assume that search is a process involving comparisons of individual items against a target description that is based on the properties of the target in isolation. Here, we present four experiments that demonstrate that this holds true only in difficult search. In medium search it seems that the relation between the target and neighbouring items is also part of the target description.We used two sets of oriented lines to construct the search items. The cardinal set contained horizontal and vertical lines, the diagonal set contained left diagonal and right diagonal lines. In all experiments, participants knew the identity of the target and the line set used to construct it. In difficult search this knowledge allowed performance to improve in displays where only half of the search items came from the same line set as the target (50% eligibility), relative to displays where all items did (100% eligibility). However, in medium search, performance was actually poorer for 50% eligibility, especially on target-absent trials.This opposite effect of ineligible items in medium search and difficult search is hard to reconcile with theories based on individual items. It is more in line with theories that conceive search as a sequence of fixations where the number of items processed during a fixation depends on the difficulty of the search task: When search is medium, multiple items are processed per fixation. But when search is difficult only a single item is processed

Spatial clustering and its effect on perceived clustering, numerosity, and dispersion

Human observers are able to estimate the numerosity of large sets of visual elements. The occupancy model of perceived numerosity in intermediate numerical ranges is based on overlapping regions of influence. The key idea is that items within a certain range count for less than their actual numerical value and more so the closer they are to their neighbours. Therefore occupancy is sensitive to the grouping of elements, but there are other spatial properties of configurations that could also influence perceived numerosity, such as: area of convex hull, occupancy area, total degree of connectivity, and local clustering For all indices apart from convex hull, we varied the radius of the area that defined neighbours. We tested perceived numerosity using a fixed number of elements placed at random within a circular region. Observers compared two patterns (presented in two intervals) and chose the one that appeared more numerous. The same observers performed two other separate tasks in which they judged which pattern appeared more dispersed or more clustered. In each pair of images, the number was always the same (22, 28, 34, or 40 items), because we were interested in which "appeared" more numerous on the basis of spatial configuration. The results suggest that estimates of numerosity, dispersion, and clustering are based on different spatial information, that there are alternative approaches to quantifying clustering, and that in all cases clustering is linked to a decrease in perceived numerosity. The alternative measures have different properties and different practical and computational advantages.</p

Proneness to decreased negative emotions in major depressive disorder when blaming others rather than oneself

&lt;b&gt;&lt;i&gt;Background:&lt;/i&gt;&lt;/b&gt; One widespread view holds that vulnerability to major depressive disorder (MDD) is linked to overall increases in negative emotionality. In contrast, cognitive attribution theories emphasize the importance of blaming oneself rather than others for negative events. Thus far, the contrasting predictions of these models have not been directly compared. Following the attributional perspective, we tested the hypothesis that people with remitted MDD show no overall bias towards negative emotions, but a selective bias towards self-blaming emotions relative to those emotions associated with blaming others. &lt;b&gt;&lt;i&gt;Sampling and Methods:&lt;/i&gt;&lt;/b&gt; We compared a remitted MDD and a control group on a novel experimental test that allowed us to directly compare proneness to specific emotions associated with different types of self-blame (guilt, shame, self-contempt/disgust) and blame of others (other-indignation/anger, other-contempt/disgust) whilst controlling for negative valence and medication status, and excluding comorbidity. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; In agreement with our hypothesis, individuals with remitted MDD exhibited an increased self-contempt bias (difference between contempt/disgust towards self and others) but no increased proneness to any other negative emotion or overall increases in perceived negative valence of stimuli. Moreover, the remitted MDD group exhibited reduced contempt/disgust towards others. &lt;b&gt;&lt;i&gt;Conclusions:&lt;/i&gt;&lt;/b&gt; Our results corroborate the prediction that vulnerability to MDD is associated with an imbalance of specific self- and other-blaming emotions rather than a general increase in negative emotions. Based on the composition of our sample, we speculate that self-contempt bias may be particularly characteristic of melancholic MDD subtypes and could be useful for stratification of depression in the future.</jats:p

Looming motion primes the visuomotor system.

A wealth of evidence now shows that human and animal observers display greater sensitivity to objects that move toward them than to objects that remain static or move away. Increased sensitivity in humans is often evidenced by reaction times that increase in rank order from looming, to receding, to static targets. However, it is not clear whether the processing advantage enjoyed by looming motion is mediated by the attention system or the motor system. The present study investigated this by first examining whether sensitivity is to looming motion per se or to certain monocular or binocular cues that constitute stereoscopic motion in depth. None of the cues accounted for the looming advantage. A perceptual measure was then used to examine performance with minimal involvement of the motor system. Results showed that looming and receding motion were equivalent in attracting attention, suggesting that the looming advantage is indeed mediated by the motor system. These findings suggest that although motion itself is sufficient for attentional capture, motion direction can prime motor responses. © 2013 American Psychological Association

Spreading the sparing: Against a limited-capacity account of the attentional blink.

The identification of the second of two targets presented in close succession is often impaired-a phenomenon referred to as the attentional blink. Extending earlier work (Di Lollo, Kawahara, Ghorashi, and Enns, in Psychological Research 69:191-200, 2005), the present study shows that increasing the number of targets in the stream can lead to remarkable improvements as long as there are no intervening distractors. In addition, items may even recover from an already induced blink whenever they are preceded by another target. It is shown that limited memory resources contribute to overall performance, but independent of the attentional blink. The findings argue against a limited-capacity account of the blink and suggest a strong role for attentional control processes that may be overzealously applied. © 2005 Springer-Verlag