Why is it so difficult for neuroscience to identify where our self-experience comes from? It seems to involve a number of processes: memory, emotion, perception, action. Knoblich and Sebanz review some work on self. (see citation)
Action has recently become a central topic in research addressing the sense of self because there is converging evidence that the ability to experience oneself as the cause of an action (self- agency) might be the fundamental building block supporting the sense of self in general. In a recent article, Atsushi Sato and Asako Yasuda report a series of elegant and thought-provoking experiments in which they explored the role of prediction for the experience of agency.
Here in a nut-shell is the Sato Yasuda protocol:
At the beginning of each of Sato and Yasudas experiments, the participants acquired an arbitrary mapping between two actions (left and right button press) and two auditory consequences (high or low tone). Thus, they learned that their action consistently produced a particular auditory effect at a particular time. In the second phase, two factors were varied: the congruency of the auditory effect in relation to the acquired action-effect mapping and the temporal delay between action and effect. The tone following each action either corresponded to the earlier acquired mapping (congruent) or not (incongruent). The temporal delay between action and effect varied between 0 ms and 600 ms. Participants were told that the auditory effects could be the result of their own action or the experimenters action. Participants reported to which extent they felt the tone to be a consequence of their own action.
The results showed that the congruency between the action and its auditory effect, and the temporal delay contributed independently to the experience of agency. This is the pattern both when the subjects choose when to act and when they reacted to a stimuli. The experience of agency decreased with increased temporal lag.
There are a number of conclusions in the original paper:
The authors interpret these findings as evidence that the experience of agency depends on a comparison between the predicted and the actual sensory consequences of an action. This is in line with the internal model theory of motor control, which postulates that for each action that is executed a prediction of its sensory consequences is generated. This prediction is compared with the actual consequences of an action. The larger the discrepancy the less likely it is that one experiences oneself as causing the action.
The feeling of agency was affected whether the action was freely chosen or performed in reaction to an external signal but the effects of the temporal delay were more pronounced when actions were freely chosen.
This raises an interesting possibility: in reactive tasks actors might completely lose the experience of agency when there is a long delay between action and effect, whereas in active tasks the experience of agency is preserved to a considerable extent. Using this clever technique the authors were able to demonstrate that the congruency between action and effect and the delay between them had an effect on the experience of agency both for intended and for erroneous actions. This result supports the authors assumption that the experience of agency depends on the discrepancy between predicted and actual sensory consequences, regardless of whether an action is intended or is a mistake. However, an additional result qualifies this interpretation: when there was no temporal delay, the experience of agency was less intense for erroneous actions than for intended actions. Thus, the full-fledged experience of agency requires an action to be intended and its effects to be both congruent and temporally contingent (with prediction).
The reviewers point out that there are other theories that fit the results.
Some researchers in the field of voluntary action postulate that the sense of agency does not rely on predictive mechanisms, but on a post-hoc evaluation of performed actions. In particular, Wegner has proposed that the illusionary feeling of causing an action arises based on priority (thought precedes action), consistency (thought consistent with action), and exclusivity (no alternative causes). In Sato and Yasudas experiments priority was always given, because an intention to act preceded the consequence. Exclusivity was never given, because participants believed that another agent could cause the perceived action consequences. Consistency was manipulated in different ways. It was absent or reduced when the action effect was incongruent, when there was a temporal delay between action and effect, and when an erroneous action was made. ..
A further explanation for experienced agency for unintentional actions is suggested by recent studies on error monitoring (Yordonova, Van Schie). It is well known that after an erroneous action is selected internal monitoring mechanisms signal that one has committed an error. Such error signals are based on the detection of a conflict that occurred while choosing between several action alternatives rather than on the comparison between the predicted and actual consequences of a specific action selected for
execution. Agency for erroneous actions could be experienced because an error-monitoring signal is used to readjust the system. The readjustment could serve as a direct indication of agency, or it could influence post-hoc evaluations of performed actions. ..
In addition to studies using explicit judgments of agency at least two further lines of research have used implicit perceptual measures. Haggard and his colleagues have
demonstrated that an action and its effect are perceived as being closer in time when the consequence is intended. Blakemore and collaborators have shown that the same sensation is experienced as less intense when arising from a self-performed action than when arising
from an other-performed action. It is not yet clear whether such changes in sensation and perception are caused by the same mechanisms that inform explicit judgments of agency.
Are these ideas contradictory? I believe not. The prediction and the error-monitoring mechanisms may (I think probably) are the same. And this predictive error system would be an important part of Wegner’s theory.
Knoblich, G., & Sebanz, N. (2005). Agency in the face of error Trends in Cognitive Sciences, 9 (6), 259-261 DOI: 10.1016/j.tics.2005.04.006
Sato, A., & Yasuda, A. (2005). Illusion of sense of self-agency: discrepancy between the predicted and actual sensory consequences of actions modulates the sense of self-agency, but not the sense of self-ownership Cognition, 94 (3), 241-255 DOI: 10.1016/j.cognition.2004.04.003