Ben-Shahar, O., Scholl, B. J., & Zucker, S. (2003). Where objects come from: Attention, segmentation, and textons. Poster presented at the annual meeting of the Vision Sciences Society, 5/10/03, Sarasota, FL.
It is well established that the units of attention are not merely spatial but closely relate to perceptual objects. While much work in the field of object-based attention (OBA) is aimed at finding these units, their relationship to the basic features (textons) that guide the segmentation of visual stimuli into 'objects' is largely unexplored. Here we bridge this gap for one of the most conspicuous features of early vision, namely orientation. Much work in the segmentation literature suggests that orientation-based texture segmentation (OBTS) is guided by orientation gradients, and our previous work also suggests that it is also significantly mediated by texture flow curvatures. In addition, this work makes the surprising prediction that the flow of attention should *not* depend on the general direction (i.e. the 'grain') of the texture -- in contradiction to previous findings in the OBA literature (Avrahami, 1999). To address this contradiction and to reveal the relationship between attention, objects, OBTS, and the orientation texton, we employ both the cueing and divided-attention paradigms on various orientation-defined textures (ODTs), both uniform (one 'object') and discontinuous (two 'objects'). Contrary to previous studies, we find that the texture's 'main direction' has no effect: attention flows just as readily with vs. against the 'grain' of ODTs. At the same time, texture-defined discontinuities have a major effect: attention flows less readily across texture-defined boundaries which are defined by both orientation and curvature. These effects replicated across multiple paradigms and dependent measures, and also held for jittered ODTs, wherein the effects must be due to the global structure and not local good continuation. We conclude that uniform ODTs are single objects from an attentional point of view, while discontinuous ODTs are processed as multiple objects. This work reveals how the 'objects' of OBA are formed from simple visual features.
Choi, H., & Scholl, B. J. (2003). Effects of grouping and attention on the perception of causality. Poster presented at the annual meeting of the Vision Sciences Society, 5/11/03, Sarasota, FL.
Beyond perceiving patterns of motion in simple dynamic displays, we can also perceive higher level properties such as *causality*, as when we see one object *collide* with another object. Though causality is a seemingly high-level property, its perception -- like the perception of faces or speech -- often appears to be automatic, irresistible, and driven by highly constrained and stimulus-driven 'rules'. Our goal, following Michotte, is to discover these rules. Consider a disc (A) which moves toward a stationary disc (B) until they are adjacent, at which point A stops and B starts moving along the same path. We perceive this event as a 'launch': A smashes into B, causing its motion. When A and B fully overlap before B starts moving, however, the display is ambiguous: in addition to launching, observers often perceive a 'pass' wherein a single moving object simply passes over another stationary object. In a series of experiments, we demonstrate that perceptual grouping and attention can heavily influence whether such ambiguous events are perceived as causal. When a single additional disc (C) is added to the display, its motion can determine the percept. When C always stays aligned with B, subjects reliably perceive A & B as causal launching; when C always remains stationary (even after B moves), subjects reliably perceive A & B as noncausal passing. In this and many related experiments which we will demonstrate, we thus show that grouping induced by either connectedness or common motion can influence causal perception. We further suggest that such grouping effects are mediated by attention, and in other experiments we directly demonstrate that attention can both promote and attenuate causal perception. Like Michotte, we find that the perception of causality is mediated by strict visual 'rules'. Beyond Michotte, we find that these rules operate not only over the objects involved in an event, but over additional objects, constrained by the allocation of attention.
Mitroff, S. R., Scholl, B. J., & Wynn, K. (2003). The relationship between object files and conscious perception. Poster presented at the annual meeting of the Vision Sciences Society, 5/9/03, Sarasota, FL.
Many aspects of mid-level vision appear to operate on the basis of representations which precede identification and recognition, but in which discrete objects are segmented from the background and tracked over time (unlike early sensory representations). It has become increasingly common to discuss such phenomena in terms of 'object files' (OFs) -- critical mid-level representations which help mediate our conscious perception of persisting objects -- e.g. telling us 'which went where'. Despite the appeal of the OF framework, it remains unclear to what degree OFs underlie consciously perceived object trajectories. Here we present at least one case wherein conscious percepts of 'which went where' in dynamic displays diverge from the computation of 'which went where' in the OF system. Observers viewed an ambiguous 'bouncing/streaming' display in which two identical objects moved such that they could have either streamed past or bounced off each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit object-specific priming (OSP) measure, wherein a 'preview' of information on a specific object -- e.g. a letter that flashes inside a small box -- speeds the recognition of that letter at a later point when it appears again on the same box (compared to when it reappears on a different box). When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 90% of the trials), there was nevertheless a strong *negative* OSP associated with the streaming motion, such that the OSP appeared to have 'bounced' even though the percept 'streamed'. Given that OSP measures have been taken as a hallmark of the operation of object files, this suggests that in at least some cases conscious percepts of 'which went where' in dynamic ambiguous displays can override the mapping computed by the object-file system.
Noles, N. S., & Scholl, B. J. (2003). The persistence of object-file representations. Poster presented at the annual meeting of the Vision Sciences Society, 5/9/03, Sarasota, FL.
Coherent visual experience of dynamic scenes requires not only that the visual system segment scenes into component objects, but that these object representations *persist*, so that an object can be identified as the same object from an earlier time. Object-files (OFs) are visual representations thought to mediate such abilities: OFs lie between lower-level sensory processing and higher-level recognition, and track salient objects over time and motion. OFs can be studied with object-specific priming (OSP): discriminations of an object's features are speeded when an earlier preview of those features occurs on the same object, beyond general priming. Despite its popularity, many fundamental aspects of the OF framework remain unexplored. For example, though OFs are thought to be involved primarily in online visual processing, we do not know how long such representations persist: previous studies found OSP for up to 750 ms, but did not test longer durations. We explored this issue using a modified 'object reviewing' paradigm, and found that robust OSP effects persist for up to 5 times as long as previously tested values (at least 4 s), and possibly much longer. We will demonstrate such effects, and discuss manipulations that affect the duration over which OSP is observed. The fact that OFs persist for extended durations raises the possibility that they may be involved in other sorts of perceptual processing, across longer durations. These findings also bear on research in infant cognition, where OFs are thought to explain infants' abilities to track and enumerate small sets of objects. Because such infancy experiments typically involve longer delays, the extended persistence we observe raises the possibility that the same OF representations may be operating in infancy and adult visual cognition. Object files may be involved primarily in momentary online processing, but they can also persist to support the identification of persisting objects across temporal gaps.
Scholl, B. J., Noles, N. S., Pasheva, V., & Sussman, R. (2003). Talking on a cellular telephone dramatically increases 'sustained inattentional blindness'. Paper read at the annual meeting of the Vision Sciences Society, 5/13/03, Sarasota, FL.
In daily life attention is constantly spread not just across computer displays, but across several modalities, tasks, and objects, and it is unclear how attention operates in such realistic situations. Here we report a striking effect of sustained inattentional blindness (SIB) induced by one particularly relevant attention-demanding task: talking on a cellular telephone. Much research has shown that talking on a cellphone will slow responses, increase performance errors, and degrade detailed visual memory. But while some traffic accidents are no doubt caused by such factors, many have a different cause: Why did I hit the the other car? Because I didn't *see* it! Here we report a first test of the impact of cellphone use on visual awareness. Observers viewed a dynamic display containing many moving items with various features, and were given a 'multiple object tracking' (MOT) task. Observers completed 3 trials, then on the 4th trial an unexpected event (UE) occurred: a new salient object suddenly entered and passed across the display, fully visible and in motion for 5 s. Observers were then probed in several ways for their awareness of the UE, and as in other studies many observers -- 30% -- were 'inattentionally blind', and completely failed to perceive the UE. Another group of observers completed the identical task, but also had a cellphone conversation with a confederate during the experiment. These observers were no less accurate at the overt MOT task, but their level of SIB skyrocketed to 90%! The nature of this impairment was refined in several additional controls, in which subjects had to talk but not listen to the confederate, listen but not talk, or mindlessly shadow a list of words. The massive jumps in SIB caused by the cellphone conversations and other cognitively engaging controls suggests a sobering conclusion: that visual *awareness* is particularly impaired by cellphone conversations, above and beyond any smaller effects on visual performance.
vanMarle, K., & Scholl, B. J. (2003). Attentive tracking of objects vs. substances. Poster presented at the annual meeting of the Vision Sciences Society, 5/11/03, Sarasota, FL.
Recent research in vision science, infant cognition, and word-learning all suggest a special role for the processing of individual discrete objects. But what counts as an object? Answers to this question often depend on contrasting object-based processing with the processing of spatial areas, or unbound visual features. In infant cognition and word-learning, though, another salient contrast has been between rigid cohesive objects and nonsolid substances. Whereas objects may move from one location to another, a nonsolid substance must *pour* from one location to another. Here we explore whether attentive tracking processes are sensitive to dynamic information of this type. We employ the multiple-object tracking task, wherein observers are presented with an array of identical items, a subset are briefly highlighted as targets, and observers must use attention to keep track of the targets as all of the items move randomly about the display -- so that they can indicate the targets at the end of a 20-second tracking period. We find that observers can easily track 4 in 8 identical unpredictably-moving items which move as discrete objects from one location to another, but cannot track similar entities which noncohesively 'pour' from one location to another -- even when the items in both conditions follow the same trajectories at the same speeds. Other conditions reveal that the inability to track multiple 'substances' stems not from the violations of rigidity or cohesiveness per se, since subjects are able to track multiple non-cohesive collections and multiple non-rigid deforming objects. Rather, the impairment is due to the dynamic extension and contraction during the 'substance-like' motion, which render 'the' location of the entity ambiguous. We will demonstrate these and other effects, which suggest a convergence between processes of mid-level adult vision and infant cognition, and in general help to clarify what can count as a persisting dynamic 'object' of attention.