Walter Bischof | University of Alberta (original) (raw)

Papers by Walter Bischof

Psychological Bulletin, 1995

Psychonomic Bulletin & Review, 1999

When two targets (T1 and T2) are displayed in rapid succession, accuracy of T2 identification var... more When two targets (T1 and T2) are displayed in rapid succession, accuracy of T2 identification varies as a function of the temporal lag between the targets (attentional blink, AB). In some studies, performance has been found to be most impaired at Lag 1—namely, when T2 followed T1 directly. In other studies, T2 performance at Lag 1 has been virtually unimpaired (Lag 1 sparing). In the present work, we examined how Lag 1 sparing is affected by attentional switches between targets displayed in the same location or in different locations. We found that Lag 1 sparing does not occur when a spatial shift is required between T1 and T2. This suggests that attention cannot be switched to a new location while the system is busy processing another stimulus. The results are explained by a modified version of an attentional gating model (Chun & Potter, 1995; Shapiro & Raymond, 1994).

Attention Perception & Psychophysics, 2004

When two sequential targets (T1 and T2) are presented within about 600 msec, perception of the se... more When two sequential targets (T1 and T2) are presented within about 600 msec, perception of the second target is impaired. This attentional blink (AB) has been studied by means of two paradigms: rapid serial visual presentation (RSVP), in which targets are embedded in a stream of central distractors, and the two-target paradigm, in which targets are presented eccentrically without distractors. We examined the role of distractors in the AB, using a modified two-target paradigm with a central stream of task-irrelevant distractors. In six experiments, the RSVP stream of distractors substantially impaired identification of both T1 and T2, but only when the distractors shared common characteristics with the targets. Without such commonalities, the distractors had no effect on performance. This points to the subjects’ attentional control setting as an important factor in the AB deficit and suggests a conceptual link between the AB and a form of nonspatial contingent capture attributable to distractor processing.

Psychological Bulletin, 1999

Journal of The Optical Society of America A-optics Image Science and Vision, 1995

Coherent directional motion can be seen if an image is displayed in two sequential frames ( F1 an... more Coherent directional motion can be seen if an image is displayed in two sequential frames ( F1 and F2), where F2 is a translated version of F1. A similar two-frame sequence can produce metacontrast masking: the visibility of a leading target ( F1) is reduced by a trailing, spatially nonoverlapping mask ( F2). Strict temporal succession of the stimuli has been considered essential for both motion and masking. This requirement for a minimum stimulus-onset asynchrony (SOA) is known as the SOA law. Contrary to the SOA law, we found that motion and masking can be obtained with simultaneous onsets of the stimuli, provided that F2 outlasts F1. We compared motion and metacontrast with simultaneous onsets of the stimuli (SIM paradigm) with the traditional paradigm in which an interstimulus interval ( ISI ) is inserted between the leading and the trailing stimuli ( ISI paradigm). We studied the effects in light-adapted and in dark-adapted viewing, each over a wide range of stimulus intensities. Homologous results were obtained with the two paradigms, thus disconfirming the SOA law. Models of motion sensors, such as that proposed by Reichardt [in Sensory Communication, W. A. Rosenblith, ed. ( MIT Press, Cambridge, Mass., 1961), p. 303], are inherently capable of explaining the motion results obtained with both paradigms. The masking results with the SIM paradigm disconfirm theories based on onset-locked slow excitatory and fast inhibitory responses but can be explained in terms of Bridgeman's network model [ Bull. Math. Biol. 40, 605 (1978)]. In light of the results obtained with the two paradigms, we discuss, and tentatively support, the suggestion that motion and metacontrast may be complementary parts of a unitary perceptual system.

Brain Research, 2006

We sought to understand what types of information people use when they infer the attentional stat... more We sought to understand what types of information people use when they infer the attentional states of others. In our study, two groups of participants viewed pictures of social interactions. One group was asked to report where the people in the pictures were directing their attention and how they (the group) knew it. The other group was simply asked to describe the pictures. We recorded participants' eye movements as they completed the different tasks and documented their subjective inferences and descriptions. The findings suggest that important cues for inferring attention of others include direction of eye gaze, head position, body orientation, and situational context. The study illustrates how attention research can benefit from (a) using more complex real-world tasks and stimuli, (b) measuring participants' subjective reports about their experiences and beliefs, and (c) observing and describing situational behavior rather than seeking to uncover some putative basic mechanism(s) of attention. Finally, we discuss how our research points to a new approach for studying human attention. This new approach, which we call Cognitive Ethology, focuses on understanding how attention operates in everyday situations and what people know and believe about attention. Cognitive ethology Eye monitoring Inferring attention Subjective report Meaning B R A I N R E S E A R C H 1 0 8 0 ( 2 0 0 6 ) 1 0 1 -1 1 9 ⁎ Corresponding ava i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s ev i e r. c o m / l o c a t e / b r a i n r e s

Visual Cognition, 2008

A great deal of recent research has sought to understand the factors and neural systems that medi... more A great deal of recent research has sought to understand the factors and neural systems that mediate the orienting of spatial attention to a gazed-at location. What have rarely been examined, however, are the factors that are critical to the initial selection of gaze information from complex visual scenes. For instance, is gaze prioritized relative to other possible body parts and objects within a scene? The present study springboards from the seminal work of , who had originally examined participants' scan paths while they viewed visual scenes containing one or more people. His work suggested to us that the selection of gaze information may depend on the task that is assigned to participants, the social content of the scene, and/or the activity level depicted within the scene. Our results show clearly that all of these factors can significantly modulate the selection of gaze information. Specifically, the selection of gaze was enhanced when the task was to describe the social attention within a scene, and when the social content and activity level in a scene were high. Nevertheless, it is also the case that participants always selected gaze information more than any other stimulus. Our study has broad implications for future investigations of social attention as well as resolving a number of longstanding issues that had undermined the classic original work of Yarbus.

Quarterly Journal of Experimental Psychology, 2008

The present study examined how social attention is influenced by social content and the presence ... more The present study examined how social attention is influenced by social content and the presence of items that are available for attention. We monitored observers' eye movements while they freely viewed real-world social scenes containing either 1 or 3 people situated among a variety of objects. Building from the work of we hypothesized that observers would demonstrate a preferential bias to fixate the eyes of the people in the scene, although other items would also receive attention. In addition, we hypothesized that fixations to the eyes would increase as the social content (i.e., number of people) increased. Both hypotheses were supported by the data, and we also found that the level of activity in the scene influenced attention to eyes when social content was high. The present results provide support for the notion that the eyes are selected by others in order to extract social information. Our study also suggests a simple and surreptitious methodology for studying social attention to real-world stimuli in a range of populations, such as those with autism spectrum disorders.

Journal of Experimental Psychology-human Perception and Performance, 2003