The Implicit Processing in Multiple Object Tracking (original) (raw)
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A single unexpected change in target- but not distractor motion impairs multiple object tracking
Recent research addresses the question whether motion information of multiple objects contributes to maintaining a selection of objects across a period of motion. Here, we investigate whether target and/or distractor motion information is used during attentive tracking. We asked participants to track four objects and changed either the motion direction of targets, the motion direction of distractors, neither, or both during a brief flash in the middle of a tracking interval. We observed that a single direction change of targets is sufficient to impair tracking performance. In contrast, changing the motion direction of distractors had no effect on performance. This indicates that target-but not distractor motion information is evaluated during tracking.
Visual Attention is Required for Multiple Object Tracking
Journal of Vision, 2013
In the multiple object tracking task, participants attempt to keep track of a moving set of target objects embedded in an identical set of moving distractors. Depending on several display parameters, observers are usually only able to accurately track 3 to 4 objects. Various proposals attribute this limit to a fixed number of discrete indexes (Pylyshyn, 1989), limits in visual attention (Cavanagh & Alvarez, 2005), or "architectural limits" in visual cortical areas (Franconeri, 2013). The present set of experiments examined the specific role of visual attention in tracking using a dual-task methodology in which participants tracked objects while identifying letter probes appearing on the tracked objects and distractors. As predicted by the visual attention model, probe identification was faster and/or more accurate when probes appeared on tracked objects. This was the case even when probes were more than twice as likely to appear on distractors suggesting that some minimum amount of attention is required to maintain accurate tracking performance. When the need to protect tracking accuracy was relaxed, participants were able to allocate more attention to distractors when probes were likely to appear there but only at the expense of large reductions in tracking accuracy. A final experiment showed that people attend to tracked objects even when letters appearing on them are task-irrelevant, suggesting that allocation of attention to tracked objects is an obligatory process. These results support the claim that visual attention is required for tracking objects.
Attentional enhancement during multiple-object tracking
Psychonomic Bulletin & Review, 2009
What is the role of attention in multiple-object tracking? Does attention enhance target representations, suppress distractor representations, or both? It is difficult to ask this question in a purely behavioral paradigm without altering the very attentional allocation one is trying to measure. In the present study, we used event-related potentials to examine the early visual evoked responses to task-irrelevant probes without requiring an additional detection task. Subjects tracked two targets among four moving distractors and four stationary distractors. Brief probes were flashed on targets, moving distractors, stationary distractors, or empty space. We obtained a significant enhancement of the visually evoked P1 and N1 components (~100-150 msec) for probes on targets, relative to distractors. Furthermore, good trackers showed larger differences between target and distractor probes than did poor trackers. These results provide evidence of early attentional enhancement of tracked target items and also provide a novel approach to measuring attentional allocation during tracking.
Effects of target enhancement and distractor suppression on multiple object tracking capacity
Journal of Vision, 2009
Mounting evidence suggests that visual attention may be simultaneously deployed to multiple distinct object locations, but the constraints upon this multi-object attentional system are still debated. Results from multiple object tracking (MOT) experiments have been interpreted as revealing a fixed attentional capacity limit of 4 objects, while other evidence has suggested that attentional capacity may be more fluid. Here, we investigated the influence of target stimulus factors, such as speed and size, and of distractor filtering factors, such as number of distractors and screen density, on MOT performance. Each factor had significant effects on capacity, producing values that ranged from above 6 objects down to one object, depending on the task demands. Although our results support the view that crowding effects modulate the effective capacity of attention, we also find evidence that central processes related to distractor suppression and target enhancement modulate capacity.
The rich literature on multiple object tracking (MOT) conclusively demonstrates that humans are able to visually track a small number of objects. There is considerably less agreement on what perceptual and cognitive processes are involved. While it is clear that MOT is attentionally demanding, various accounts of MOT performance centrally involve pre-attentional mechanisms as well. In this paper we present an account of object tracking in the ARCADIA cognitive system that treats MOT as dependent upon both preattentive and attention-bound processes. We show that with minimal addition this model replicates a variety of core phenomena in the MOT literature and provides an algorithmic explanation of human performance limitations.
Target enhancement and distractor suppression in multiple object tracking
2010
In multiple object tracking (MOT), observers keep track of target objects that move haphazardly around a display in the presence of identical distractors. The typical result from this paradigm is that observers can accurately track up to about four objects, with performance declining precipitously beyond this number.
The Role of Implicit Context Information in Guiding Visual-Spatial Attention
Lecture Notes in Computer Science, 2008
Flexibility and adaptability are desirable features of cognitive technical systems. However, in comparison to humans, the development of these features for technical systems is still at the beginning. One approach to improve their realization is to study human cognitive processes and to develop appropriate algorithms, which can be transferred and implemented into technical systems. One example for a typical task common to humans and robots is to find a specific task-relevant object (or target) among other similar but task-irrelevant objects (or distractors). Although this task is quite demanding, humans are doing well in finding task-relevant objects even in unknown environments by applying specific search strategies. For example, when an object is located in a familiar rather than in a new context, humans use the context information to localize the object without recognizing the context as familiar. This phenomenon is known as contextual cueing: it is supposed that implicitly learned context information of the environment, i.e. the spatial layout of objects and their relations, guides visual-spatial attention to the target location and thus helps to localize the task-relevant object.
The main goal of our research was to investigate attention to dynamic visual stimuli. Observers were instructed to attentively track a variable number of moving visual objects for a sustained period of several minutes. At random intervals, a target stimulus of brief duration was presented inside one of these objects and observers were required to identify it. The number of relevant objects to be tracked and the grouping strength among objects that had to be attended, operationalized as the size of relative area among those objects, were manipulated. The results indicated that only a single object could be attentively tracked, unless the objects formed a perceptual group. In this case, more than one dynamic object could be attended, but effectiveness of attention would be mediated by perception of the spatial relations among them.
Many tasks involve tracking multiple moving objects, or stimuli. Some require that individuals adapt to changing or unfamiliar conditions to be able to track well. This study explores processes involved in such adaptation through an investigation of the interaction of attention and memory during tracking. Previous research has shown that during tracking, attention operates independently to some degree in the left and right visual hemifields, due to putative anatomical constraints. It has been suggested that the degree of independence is related to the relative dominance of processes of attention versus processes of memory. Here we show that when individuals are trained to track a unique pattern of movement in one hemifield, that learning can be transferred to the opposite hemifield, without any evidence of hemifield independence. However, learning is not influenced by an explicit strategy of memorisation of brief periods of recognisable movement. The findings lend support to a role for implicit memory in overcoming putative anatomical constraints on the dynamic, distributed spatial allocation of attention involved in tracking multiple objects.