Biomedical subjects

Brian J Scholl

Publications and source records attributed to Brian J Scholl.

At least 19 recordsLinked to original sources

PubMed2006

Measuring causal perception: connections to representational momentum?

In a collision between two objects, we can perceive not only low-level properties, such as color and motion, but also the seemingly high-level property of causality. It has proven difficult, however, to measure causal perception in a quantitatively rigorous way which goes beyond perceptual reports. Here we focus on the possibility of measuring perceived causality using the phenomenon of representational momentum (RM). Recent studies suggest a relationship between causal perception and RM, based on the fact that RM appears to be attenuated for causally 'launched' objects. This is explained by appeal to the visual expectation that a 'launched' object is inert and thus should eventually cease its movement after a collision, without a source of self-propulsion. We first replicated these demonstrations, and then evaluated this alleged connection by exploring RM for different types of displays, including the contrast between causal launching and non-causal 'passing'. These experiments suggest that the RM-attenuation effect is not a pure measure of causal perception, but rather may reflect lower-level spatiotemporal correlates of only some causal displays. We conclude by discussing the strengths and pitfalls of various methods of measuring causal perception.

Cognition↗

PubMed2006

Introduction to Michotte's heritage in perception and cognition research.

Several decades after Michotte's work was published, it continues to inspire current research in perception, cognition, and beyond. In this special issue we pay tribute to this heritage with a collection of empirical and theoretical papers on amodal completion and the perception of causality, two areas of research within which Michotte's work and ideas have had a lasting influence. As a background to better understand the remaining papers, we briefly sketch Michotte's life and work and the scope (in breadth and in depth) of his impact. We then review Michotte's seminal contributions to the areas covered in this special issue, some of the major research discoveries and themes in the intervening decades, and the major open questions and challenges we are still facing. We also include a sneak preview of the papers in this special issue, noting how they relate to Michotte's work and to each other. This review shows both how much influence Michotte has had on contemporary perception and cognition research, and how much important work remains to be done. We hope that the papers in this special issue will serve both to celebrate Michotte's heritage in this respect, and to inspire other investigators to continue the projects he began.

Belgium↗

PubMed2006

A temporal same-object advantage in the tunnel effect: facilitated change detection for persisting objects.

Meaningful visual experience requires computations that identify objects as the same persisting individuals over time, motion, occlusion, and featural change. This article explores these computations in the tunnel effect: When an object moves behind an occluder, and then an object later emerges following a consistent trajectory, observers irresistibly perceive a persisting object, even when the pre- and postocclusion views contrast featurally. This article introduces a new change detection method for quantifying percepts of the tunnel effect. Observers had to detect color changes in displays where several objects oscillated behind occluders and occasionally changed color. Across comparisons with several types of spatiotemporal gaps, as well as manipulations of occlusion versus implosion, performance was better when objects' kinematics gave the impression of a persisting individual. The results reveal a temporal same-object advantage: better change detection across temporal scene fragments bound into the same persisting object representations. This suggests that persisting objects are the underlying units of visual memory.

Attention↗

PubMed2006

Perceiving causality after the fact: postdiction in the temporal dynamics of causal perception.

In simple dynamic events we can easily perceive not only motion, but also higher-level properties such as causality, as when we see one object collide with another. Several researchers have suggested that such causal perception is an automatic and stimulus-driven process, sensitive only to particular sorts of visual information, and a major research project has been to uncover the nature of these visual cues. Here, rather than investigating what information affects causal perception, we instead explore the temporal dynamics of when certain types of information are used. Surprisingly, we find that certain visual events can determine whether we perceive a collision in an ambiguous situation even when those events occur after the moment of potential 'impact' in the putative collision has already passed. This illustrates a type of postdictive perception: our conscious perception of the world is not an instantaneous moment-by-moment construction, but rather is formed by integrating information presented within short temporal windows, so that new information which is obtained can influence the immediate past in our conscious awareness. Such effects have been previously demonstrated for low-level motion phenomena, but the present results demonstrate that postdictive processes can influence higher-level event perception. These findings help to characterize not only the 'rules' of causal perception, but also the temporal dynamics of how and when those rules operate.

Causality↗

PubMed2006

Units of visual individuation in rhesus macaques: objects or unbound features?

Vision begins with the processing of unbound visual features, which must eventually be bound together into object representations. Such feature binding is required for coherent visual perception, and accordingly has received a considerable amount of study in several domains. Neurophysiological work, often in monkeys, has revealed the details of how and where feature binding occurs in the brain, but methodological limitations have not allowed this research to elucidate just how feature binding operates spontaneously in real-world situations. In contrast, behavioral work with human infants has demonstrated how we use simpler unbound features to individuate and identify objects over time and occlusion in many types of events, but this work has not typically been able to isolate the role of feature binding in such processing. Here we provide a method for assessing the spontaneity and fidelity of feature binding in non-human primates, as this process is utilized in real-world situations, including simple foraging behaviors. Using both looking-time and manual-search measures in a natural environment, we show that free-ranging rhesus macaques (Macaca mulatta) spontaneously bind features in order to individuate objects across time and occlusion in dynamic events. This pattern of results demonstrates that feature binding is used in subtle ways to guide ecologically relevant behavior in a non-human animal, spontaneously and reliably, in its natural environment.

Animals↗

PubMed2006

Interrupting infants' persisting object representations: an object-based limit?

Making sense of the visual world requires keeping track of objects as the same persisting individuals over time and occlusion. Here we implement a new paradigm using 10-month-old infants to explore the processes and representations that support this ability in two ways. First, we demonstrate that persisting object representations can be maintained over brief interruptions from additional independent events - just as a memory of a traffic scene may be maintained through a brief glance in the rearview mirror. Second, we demonstrate that this ability is nevertheless subject to an object-based limit: if an interrupting event involves enough objects (carefully controlling for overall salience), then it will impair the maintenance of other persisting object representations even though it is an independent event. These experiments demonstrate how object representations can be studied via their 'interruptibility', and the results are consistent with the idea that infants' persisting object representations are constructed and maintained by capacity-limited mid-level 'object-files'.

Cognition↗

PubMed2005

The relationship between object files and conscious perception.

Object files (OFs) are hypothesized mid-level representations which mediate our conscious perception of persisting objects-e.g. telling us 'which went where'. Despite the appeal of the OF framework, not previous research has directly explored whether OFs do indeed correspond to conscious percepts. Here we present at least one case wherein conscious percepts of 'which went where' in dynamic ambiguous displays diverge from the analogous correspondence computed by the OF system. Observers viewed a 'bouncing/streaming' display in which two identical objects moved such that they could have either bounced off or streamed past each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit 'object-specific preview benefit' (OSPB), wherein a 'preview' of information on a specific object speeds the recognition of that information at a later point when it appears again on the same object (compared to when it reappears on a different object), beyond display-wide priming. When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 95% of the trials), there was nevertheless a strong OSPB in the opposite direction-such that the object files appeared to have 'bounced' even though the percept 'streamed'. Given that OSPBs have been taken as a hallmark of the operation of object files, the five experiments reported here suggest that in at least some specialized (and perhaps ecologically invalid) cases, conscious percepts of 'which went where' in dynamic ambiguous displays can diverge from the mapping computed by the object-file system.

Attention↗

PubMed2005

What you see is what you set: sustained inattentional blindness and the capture of awareness.

This article reports a theoretical and experimental attempt to relate and contrast 2 traditionally separate research programs: inattentional blindness and attention capture. Inattentional blindness refers to failures to notice unexpected objects and events when attention is otherwise engaged. Attention capture research has traditionally used implicit indices (e.g., response times) to investigate automatic shifts of attention. Because attention capture usually measures performance whereas inattentional blindness measures awareness, the 2 fields have existed side by side with no shared theoretical framework. Here, the authors propose a theoretical unification, adapting several important effects from the attention capture literature to the context of sustained inattentional blindness. Although some stimulus properties can influence noticing of unexpected objects, the most influential factor affecting noticing is a person's own attentional goals. The authors conclude that many--but not all--aspects of attention capture apply to inattentional blindness but that these 2 classes of phenomena remain importantly distinct.

Adult↗

PubMed2005

The role of salience in the extraction of algebraic rules.

Recent research suggests that humans and other animals have sophisticated abilities to extract both statistical dependencies and rule-based regularities from sequences. Most of this research stresses the flexibility and generality of such processes. Here the authors take up an equally important project, namely, to explore the limits of such processes. As a case study for rule-based generalizations, the authors demonstrate that only repetition-based structures with repetitions at the edges of sequences (e.g., ABCDEFF but not ABCDDEF) can be reliably generalized, although token repetitions can easily be discriminated at both sequence edges and middles. This finding suggests limits on rule-based sequence learning and new interpretations of earlier work alleging rule learning in infants. Rather than implementing a computerlike, formal process that operates over all patterns equally well, rule-based learning may be a highly constrained and piecemeal process driven by perceptual primitives--specialized type operations that are highly sensitive to perceptual factors.

Adult↗

PubMed2005

How does attention select and track spatially extended objects? New effects of attentional concentration and amplification.

Real-world situations involve attending to spatially extended objects, often under conditions of motion and high processing load. The present experiments investigated such processing by requiring observers to attentionally track a number of long, moving lines. Concurrently, observers responded to sporadic probes as a measure of the distribution of attention across the lines. The results revealed that attention is concentrated at the centers of lines during tracking, despite their uniformity, and that this center advantage grew as the lines became longer: Not only did observers get worse near the endpoints, but they became better at the lines' centers, as if attention became more concentrated as the objects became more extended. These results begin to show how attention is flexibly allocated in online visual processing to extended dynamic objects.

Attention↗

PubMed2005

The automaticity of visual statistical learning.

The visual environment contains massive amounts of information involving the relations between objects in space and time, and recent studies of visual statistical learning (VSL) have suggested that this information can be automatically extracted by the visual system. The experiments reported in this article explore the automaticity of VSL in several ways, using both explicit familiarity and implicit response-time measures. The results demonstrate that (a) the input to VSL is gated by selective attention, (b) VSL is nevertheless an implicit process because it operates during a cover task and without awareness of the underlying statistical patterns, and (c) VSL constructs abstracted representations that are then invariant to changes in extraneous surface features. These results fuel the conclusion that VSL both is and is not automatic: It requires attention to select the relevant population of stimuli, but the resulting learning then occurs without intent or awareness.

Attention↗

PubMed2005

The role of closure in defining the "objects" of object-based attention.

Many recent studies have concluded that the underlying units of visual attention are often discrete objects whose boundaries constrain the allocation of attention. However, relatively few studies have explored the particular stimulus cues that determine what counts as an "object" of attention. We explore this issue in the context of the two-rectangles stimuli previously used by many investigators. We first show, using both spatial-cuing and divided-attention paradigms, that same-object advantages occur even when the ends of the two rectangles are not drawn. This is consistent with previous reports that have emphasized the importance of individual contours in guiding attention, and our study shows that such effects can occur in displays that also contain grouping cues. In our divided-attention experiment, however, this contour-driven same-object advantage was significantly weaker than that obtained with the standard stimulus, with the added cue of closure--demonstrating that contour-based processes are not the whole story. These results confirm and extend the observation that same-object advantages can be observed even without full-fledged objects. At the same time, however, these studies show that boundary closure-one of the most important cues to objecthood per se-can directly influence attention. We conclude that object-based attention is not an all-or-nothing phenomenon; object-based effects can be independently strengthened or weakened by multiple cues to objecthood.

Attention↗

PubMed2005

The persistence of object file representations.

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 they track salient objects over time and motion. OFs have traditionally been studied via object-specific preview benefits (OSPBs), in which discriminations of an object's features are speeded when an earlier preview of those features occurred on the same object, as opposed to on a different object, beyond general displaywide priming. Despite its popularity, many fundamental aspects of the OF framework remain unexplored. For example, although OFs are thought to be involved primarily in online visual processing, we do not know how long such representations persist; previous studies found OSPBs for up to 1500 msec but did not test for longer durations. We explored this issue using a modified object reviewing paradigm and found that robust OSPBs persist for more than five times longer than has previously been tested-for at least 8 sec, and possibly for much longer. Object files may be the "glue" that makes visual experience coherent not just in online moment-by-moment processing, but on the scale of seconds that characterizes our everyday perceptual experiences. 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 over longer durations.

Humans↗

PubMed2004

Forming and updating object representations without awareness: evidence from motion-induced blindness.

The input to visual processing consists of an undifferentiated array of features which must be parsed into discrete units. Here we explore the degree to which conscious awareness is important for forming such object representations, and for updating them in the face of changing visual scenes. We do so by exploiting the phenomenon of motion-induced blindness (MIB), wherein salient (and even attended) objects fluctuate into and out of conscious awareness when superimposed onto certain global motion patterns. By introducing changes to unseen visual stimuli during MIB, we demonstrate that object representations can be formed and updated even without conscious access to those objects. Such changes can then influence not only how stimuli reenter awareness, but also what reenters awareness. We demonstrate that this processing encompasses simple object representations and also several independent Gestalt grouping cues. We conclude that flexible visual parsing over time and visual change can occur even without conscious perception. Methodologically, we conclude that MIB may be an especially useful tool for studying the role of awareness in visual processing and vice versa.

Awareness↗

PubMed2004

Can infants' object concepts be trained?

Decades of research and debate on the origins of object permanence in infancy have contrasted various types of learning with possible innate contributions. A recent paper by Johnson et al. adds a new perspective to this debate by reporting that even very brief training periods can dramatically influence infants' persisting object representations. Such training studies have the potential to constrain 'nature versus nurture' debates in novel ways, although important challenges remain.

Age Factors↗

PubMed2004

Illusory causal crescents: misperceived spatial relations due to perceived causality.

When an object A moves toward an object B until they are adjacent, at which point A stops and B starts moving, we often see a collision--ie we see A as the cause of B's motion. The spatiotemporal parameters which mediate the perception of causality have been explored in many studies, but this work is seldom related to other aspects of perception. Here we report a novel illusion, wherein the perception of causality affects the perceived spatial relations among two objects involved in a collision event: observers systematically underestimate the amount of overlap between two items in an event which is seen as a causal collision. This occurs even when the causal nature of the event is induced by a surrounding context, such that estimates of the amount of overlap in the very same event are much improved when the event is displayed in isolation, without a 'causal' interpretation. This illusion implies that the perception of causality does not proceed completely independently of other visual processes, but can affect the perception of other spatial properties.

Humans↗

PubMed2004

Seeing the disappearance of unseen objects.

Because of the massive amount of incoming visual information, perception is fundamentally selective. We are aware of only a small subset of our visual input at any given moment, and a great deal of activity can occur right in front of our eyes without reaching awareness. While previous work has shown that even salient visual objects can go unseen, here we demonstrate the opposite pattern, wherein observers perceive stimuli which are not physically present. In particular, we show in two motion-induced blindness experiments that unseen objects can momentarily reenter awareness when they physically disappear: in some situations, you can see the disappearance of something you can't see. Moreover, when a stimulus changes outside of awareness in this situation and then physically disappears, observers momentarily see the altered version--thus perceiving properties of an object that they had never seen before, after that object is already gone. This phenomenon of 'perceptual reentry' yields new insights into the relationship between visual memory and conscious awareness.

Awareness↗

PubMed2004

Divide and conquer: how object files adapt when a persisting object splits into two.

Coherent visual experience requires not only segmenting incoming visual input into a structured scene of objects, but also binding discrete views of objects into dynamic representations that persist across time and motion. However, surprisingly little work has explored the principles that guide the construction and maintenance of such persisting object representations. What causes a part of the visual field to be treated as the same object over time? In the cognitive development literature, a key principle of object persistence is cohesion: An object must always maintain a single bounded contour. Here we demonstrate for the first time that mechanisms of adult midlevel vision are affected by cohesion violations. Using the object-file framework, we tested whether object-specific preview benefits-a hallmark of persisting object representations-are obtained for dynamic objects that split into two during their motion. We found that these preview benefits do not fully persist through such cohesion violations without incurring significant performance costs. These results illustrate how cohesion is employed as a constraint that guides the maintenance of object representations in adult midlevel vision.

Cognition↗