Sit-and-wait strategies in dynamic visual search

The role of memory in visual search has lately become a controversial issue. Horowitz and Wolfe (1998) observed that performance in a visual search task was little affected by whether the stimuli were static or randomly relocated every 111 ms. Because a memory-based mechanism, such as inhibition of return, would be of no use in the dynamic condition, Horowitz and Wolfe concluded that memory is likewise not involved in the static condition. However, Horowitz and Wolfe could not effectively rule out the possibility that observers adopted a different strategy in the dynamic condition than in the static condition. That is, in the dynamic condition observers may have attended to a subregion of the display and waited for the target to appear there (sit-and-wait strategy). This hypothesis is supported by experimental data showing that performance in their dynamic condition does not differ from performance in another dynamic condition in which observers are forced to adopt a sit-and-wait strategy by being presented with a limited region of the display only.     

Psychotherapie und die Anerkennung des Fremden

The aim of the present paper is three-fold: it reveals the inherent limitations of the concept of disorder in psychopathology and psychotherapy. It argues that characteristics of the person such as individuality, subjectivity and identity, have to be considered in psychiatric and psychotherapeutic concepts. And it shows that psychotherapy is dependent on cultural, social and socio-economic factors that are neglected in many theories. The paper uses clinical and epistemological arguments. It arrives at the conclusion that the above mentioned limitations have a common ground. They could be overcome, if psychiatry and psychotherapy were self-reflective and self-critical in respect to the inherent limitations of theory and practice and if they integrated concepts of being different in their basic theories so that symptoms, persons and cultural or societal peculiarities could be recognised and acknowledged.—The paper has been written as a comment to D. Orlinsky's statements considering disorder-specific psychotherapies from the viewpoint of psychotherapy research.     

Accountability and cooperation in social dilemmas: The influence of others’ reputational concerns

The present study examined the assumption that non-anonymous choices in social dilemmas (i.e., choices for which one is accountable) may influence cooperation, but only to the extent that decision-makers believe that the others will evaluate non-cooperation negatively. Based on a recent review by Kerr (1999), it was expected that under conditions of accountability, decision-makers would cooperate more when they believed that the others within the group were also concerned about their social reputation and therefore were aware of the social norm of cooperation within social dilemmas. As a consequence, it could be expected that non-cooperation by oneself would be evaluated negatively by those others since they seemed to be aware of what ought to be done in a social dilemma (i.e., the norm of cooperation). Results confirmed these predictions and, in addition, also showed that greater willingness to cooperate was associated with stronger feelings of collective concern. The findings are discussed in terms of recent literature on anonymity effects in social dilemmas. This research was part of the second author's master thesis at Maastricht University. The first author was supported by a fellowship of the Netherlands Organization for Scientific Research (NWO, no. 016.005.019).     

Observing one's hand become anarchic: an fMRI study of action identification

The self seems to be a unitary entity remaining stable across time. Nevertheless, current theorizing conceptualizes the self as a number of interacting sub-systems involving perception, intention and action (self-model). One important function of such a self-model is to distinguish between events occurring as a result of one’s own actions and events occurring as the result of somebody else’s actions. We conducted an fMRI experiment that compared brain activation after an abrupt mismatch between one’s own movement and its visual consequences with an abrupt mismatch between one’s own movement and somebody else’s visually perceived hand movement. A right fronto-parietal network was selectively active during a sudden mismatch between one’s own observed and performed hand action.     

Repeated exposure of flight phobics to flights in virtual reality

The present study examined the effects of repeated exposure of flight phobics to flights in virtual reality (VR). Flight phobics were randomly assigned either to complete one VR test flight followed by four VR exposure flights (VR group; N=15) in one lengthy session or to complete one VR test flight followed by a lengthy relaxation training session (relaxation group; N=15). All participants completed a second VR test flight at the end of the session. Fear reports and physiological fear reactions (heart rate, skin conductance level) during VR exposures were registered, and fear of flying was assessed psychometrically from 3 weeks before to 3 months after exposure. Exposure to VR flights elicited subjective and physiological fear responses in flight phobics, and these responses attenuated within and across VR flights. Fear reduction associated with repeated VR exposure was greater than fear reduction caused by relaxation training. Fear of flying improved in both treatment groups, but several outcome measures indicated greater effects in the VR treated group than in the relaxation group. These findings indicate that exposure in virtual reality may offer a new and promising approach for the treatment of fear of flying.     

Visual perspective taking for avatars in a Simon task

In modern digital applications, users often interact with virtual representations of themselves or others, called avatars. We examined how these avatars and their perspectives influence stimulus–response compatibility in a Simon task. Participants responded to light/dark blue stimuli with left/right key presses in the presence of a task-irrelevant avatar. Changes in stimulus–response compatibility were used to quantify changes in the mental representation of the task and perspective taking toward this avatar. Experiments 1 and 2 showed that perspective taking for an avatar occurred in orthogonal stimulus–response mappings, causing a compatibility effect from the avatar’s point of view. In the following two experiments we introduced a larger variety of angular disparities between the participant and avatar. In Experiment 3, the Simon effect with lateralized stimulus positions remained largely unaffected by the avatar, pointing toward an absence of perspective taking. In Experiment 4, after avatar hand movements were added in order to strengthen the participants’ sense of agency over the avatar, a spatial compatibility effect from the avatar’s perspective was observed again, and hints of the selective use of perspective taking on a trial-by-trial basis were found. Overall, the results indicate that users can incorporate the perspective of an avatar into their mental representation of a situation, even when this perspective is unnecessary to complete a task, but that certain contextual requirements have to be met.     

A formal version of the Guided Search (GS2) model

Guided Search 2 (GS2) is currently one of the most detailed models of visual search and has been used to predict search times for different stimulus conditions by means of detailed computer simulations. The present article goes a step further and presents formulas that allow for the calculation of the search times and their variances. Moreover, these formulas can be applied to fit GS2 to data. An example is provided in which GS2 is fitted to search functions representing search asymmetries.     

How to produce an absent-advantage in visual search

In a series of four experiments, we investigated the conditions under which target-absent responses are faster than target-present responses in visual search. Previous experiments have shown that such an absent-advantage occurs mainly for homogeneous distractors arranged in a regular pattern. From these results, it has been concluded that the absent-advantage is due to perceptual processes, such as grouping by similarity. Our data show that such processes are not sufficient. Rather, the absent-advantage is the result of interactions between perceptual and decisional processes. Certain perceptual conditions, such as randomizing stimulus patterns, lead to specific criteria settings that produce an absent-advantage. That such an account can explain our main results is demonstrated by modeling our data with a modified version of the Guided Search 2 model.     

Walking or talking? Behavioral and neurophysiological correlates of action verb processing

Brain activity elicited by visually presented words was investigated using behavioral measures and current source densities calculated from high-resolution EEG recordings. Verbs referring to actions usually performed with different body parts were compared. Behavioral data indicated faster processing of verbs referring to actions performed with the face muscles and articulators (face-related words) compared to verbs referring to movements involving the lower half of the body (leg-related words). Significant topographical differences in brain activity elicited by verb types were found starting approximately 250 ms after word onset. Differences were seen at recording sites located over the motor strip and adjacent frontal cortex. At the vertex, close to the cortical representation of the leg, leg-related verbs (for example, to walk) produced strongest in-going currents, whereas for face-related verbs (for example, to talk) the most in-going activity was seen at more lateral electrodes placed over the left Sylvian fissure, close to the representation of the articulators. Thus, action words caused differential activation along the motor strip, with strongest in-going activity occurring close to the cortical representation of the body parts primarily used for carrying out the actions the verbs refer to. Topographically specific physiological signs of word processing started earlier for face-related words and lasted longer for verbs referring to leg movements. We conclude that verb types can differ in their processing speed and can elicit neurophysiological activity with different cortical topographies. These behavioral and physiological differences can be related to cognitive processes, in particular to lexical semantic access. Our results are consistent with associative theories postulating that words are organized in the brain as distributed cell assemblies whose cortical distributions reflect the words' meanings.     

Viewpoint dependence in visual and haptic object recognition

On the whole, people recognize objects best when they see the objects from a familiar view and worse when they see the objects from views that were previously occluded from sight. Unexpectedly, we found haptic object recognition to be viewpoint-specific as well, even though hand movements were unrestricted. This viewpoint dependence was due to the hands preferring the back "view" of the objects. Furthermore, when the sensory modalities (visual vs. haptic) differed between learning an object and recognizing it, recognition performance was best when the objects were rotated back-to-front between learning and recognition. Our data indicate that the visual system recognizes the front view of objects best, whereas the hand recognizes objects best from the back.