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Evidence from multisensory body illusions suggests that body representations may be malleable, for instance, by embodying external objects. However, adjusting body representations to current task demands also implies that external objects become disembodied from the body representation if they are no longer required. In the current web-based study, we induced the embodiment of a two-dimensional (2D) virtual hand that could be controlled by active movements of a computer mouse or on a touchpad. Following initial embodiment, we probed for disembodiment by comparing two conditions: Participants either continued moving the virtual hand or they stopped moving and kept the hand still. Based on theoretical accounts that conceptualize body representations as a set of multisensory bindings, we expected gradual disembodiment of the virtual hand if the body representations are no longer updated through correlated visuomotor signals. In contrast to our prediction, the virtual hand was instantly disembodied as soon as participants stopped moving it. This result was replicated in two follow-up experiments. The observed instantaneous disembodiment might suggest that humans are sensitive to the rapid changes that characterize action and body in virtual environments, and hence adjust corresponding body representations particularly swiftly.
A hallmark of habitual actions is that, once they are established, they become insensitive to changes in the values of action outcomes. In this article, we review empirical research that examined effects of posttraining changes in outcome values in outcome-selective Pavlovian-to-instrumental transfer (PIT) tasks. This review suggests that cue-instigated action tendencies in these tasks are not affected by weak and/or incomplete revaluation procedures (e.g., selective satiety) and substantially disrupted by a strong and complete devaluation of reinforcers. In a second part, we discuss two alternative models of a motivational control of habitual action: a default-interventionist framework and expected value of control theory. It is argued that the default-interventionist framework cannot solve the problem of an infinite regress (i.e., what controls the controller?). In contrast, expected value of control can explain control of habitual actions with local computations and feedback loops without (implicit) references to control homunculi. It is argued that insensitivity to changes in action outcomes is not an intrinsic design feature of habits but, rather, a function of the cognitive system that controls habitual action tendencies.
Body representations are readily expanded based on sensorimotor experience. A dynamic view of body representations, however, holds that these representations cannot only be expanded but that they can also be narrowed down by disembodying elements of the body representation that are no longer warranted. Here we induced illusory ownership in terms of a moving rubber hand illusion and studied the maintenance of this illusion across different conditions. We observed ownership experience to decrease gradually unless participants continued to receive confirmatory multisensory input. Moreover, a single instance of multisensory mismatch – a hammer striking the rubber hand but not the real hand – triggered substantial and immediate disembodiment. Together, these findings support and extend previous theoretical efforts to model body representations through basic mechanisms of multisensory integration. They further support an updating model suggesting that embodied entities fade from the body representation if they are not refreshed continuously.
Anticipation of one's own actions' effects drives goal-directed behavior. In multitasking environments, the learning of stable action-effect associations seems particularly important, because establishing reliable response-effect associations for multiple competing tasks may help to differentiate between these tasks and thereby improve task-switching performance. Action-effects not only have cognitive, but also motivational aspects and often the consequences of our actions are hedonically marked. Thus, the anticipated hedonic quality of action-effects may also become part of the task representation, and positive and negative affect may distinctly modulate task-switching performance. We report a pre-registered experiment (N = 120) designed to examine how positive, negative, and neutral valence of action-effects impact performance in a cued task-switching paradigm. Pictures from the IAPS database were used to manipulate the action-effects' valence. Affective valence determined reaction times: participants who learned positive or negative action-effects responded faster than participants in the control condition. In particular, task-switch trials were faster in both conditions than in the control condition, while task-repetition trials were comparable across valence conditions. Our results further suggest that performance improvements in the positive and negative valence conditions occurred for different reasons. Negative action-effects expedited responses specifically for the task that produced the unpleasant outcome, while positive affect more generally promoted performance of both tasks. These findings point toward distinct roles of positive and negative valence of action-effects in regulating multitasking performance.