Publications of Sebanz, Natalie

When do humans spontaneously adopt another’s visuospatial perspective?

Perspective-taking is a key component of social interactions. However, there is an ongoing controversy about whether, when and how instances of spontaneous visuospatial perspective-taking occur. The aim of this study was to investigate the underlying factors as well as boundary conditions that characterize the spontaneous adoption of another person's visuospatial perspective (VSP) during social interactions. We used a novel paradigm, in which a participant and a confederate performed a simple stimulus-response (SR) compatibility task sitting at a 90° angle to each other. In this set-up, participants would show a spatial compatibility effect only if they adopted the confederate's VSP. In a series of 5 experiments we found that participants reliably adopted the VSP of the confederate, as long as he was perceived as an intentionally acting agent. Our results therefore show that humans are able to spontaneously adopt the differing VSP of another agent and that there is a tight link between perspective-taking and performing actions together. The results suggest that spontaneous VSP-taking can effectively facilitate and speed up spatial alignment processes accruing from dynamic interactions in multiagent environments.

The joint Flanker effect: Sharing tasks with real and imagined co-actors

The Eriksen flanker task (Eriksen and Eriksen in Percept Psychophys 16:143-149, 1974) was distributed among pairs of participants to investigate whether individuals take into account a co-actor's S-R mapping even when coordination is not required. Participants responded to target letters (Experiment 1) or colors (Experiment 2) surrounded by distractors. When performing their part of the task next to another person performing the complementary part of the task, participants responded more slowly to stimuli containing flankers that were potential targets for their co-actor (incompatible trials), compared to stimuli containing identical, compatible, or neutral flankers. This joint Flanker effect also occurred when participants merely believed to be performing the task with a co-actor (Experiment 3). Furthermore, Experiment 4 demonstrated that people form shared task representations only when they perceive their co-actor as intentionally controlling her actions. These findings substantiate and generalize earlier results on shared task representations and advance our understanding of the basic mechanisms subserving joint action.

Observing shared attention modulates gaze following

Humans' tendency to follow others' gaze is considered to be rather resistant to top-down influences. However, recent evidence indicates that gaze following depends on prior eye contact with the observed agent. Does observing two people engaging in eye contact also modulate gaze following? Participants observed two faces looking at each other or away from each other before jointly shifting gaze to one of two locations. Targets appeared either at the cued location or at the non-cued location. In three experiments gaze cueing effects (faster responses to objects appearing at the cued location) were found only when the two faces had looked at each other before shifting gaze. In contrast, no effects of gaze following were observed when the two faces had looked away from each other. Thus, the attentional relation between observed people modulates whether their gaze is followed.

Making oneself predictable: Reduced temporal variability facilitates joint action coordination

Performing joint actions often requires precise temporal coordination of individual actions. The present study investigated how people coordinate their actions at discrete points in time when continuous or rhythmic information about others' actions is not available. In particular, we tested the hypothesis that making oneself predictable is used as a coordination strategy. Pairs of participants were instructed to coordinate key presses in a two-choice reaction time task, either responding in synchrony (Experiments 1 and 2) or in close temporal succession (Experiment 3). Across all experiments, we found that coactors reduced the variability of their actions in the joint context compared with the same task performed individually. Correlation analyses indicated that the less variable the actions were, the better was interpersonal coordination. The relation between reduced variability and improved coordination performance was not observed when pairs of participants performed independent tasks next to each other without intending to coordinate. These findings support the claim that reducing variability is used as a coordination strategy to achieve predictability. Id

No evidence of contagious yawning in the red-footed tortoise Geochelone carbonaria

Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli: the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions: observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions: real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes.