Time warp: Authorship shapes the perceived timing of actions and events

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Abstract

It has been proposed that inferring personal authorship for an event gives rise to intentional binding, a perceptual illusion in which one’s action and inferred effect seem closer in time than they otherwise would (Haggard, Clark, & Kalogeras, 2002). Using a novel, naturalistic paradigm, we conducted two experiments to test this hypothesis and examine the relationship between binding and self-reported authorship. In both experiments, an important authorship indicator – consistency between one’s action and a subsequent event – was manipulated, and its effects on binding and self-reported authorship were measured. Results showed that action-event consistency enhanced both binding and self-reported authorship, supporting the hypothesis that binding arises from an inference of authorship. At the same time, evidence for a dissociation emerged, with consistency having a more robust effect on self-reports than on binding. Taken together, these results suggest that binding and self-reports reveal different aspects of the sense of authorship.

Introduction

A central problem agents face is determining which events they have caused, and which they have not. When a room goes dark, it could be because one flipped the light switch, but it could also be because someone else in the room clapped, or because somewhere else a butterfly flapped its wings (straight into a power line, perhaps). It has been proposed that to solve this problem of authorship, the mind must weigh a variety of authorship indicators and arrive at an appropriate causal inference (Wegner, 2002, Wegner and Sparrow, 2004). An important authorship indicator is the temporal contiguity between one’s action and a subsequent event (Shanks, Pearson, & Dickinson, 1989), which is a special case of the more general principle that causality is perceived when an event is followed closely by another (Hume, 1888, Michotte, 1963). When one’s flip of the switch is followed immediately by the room’s going dark, one can be more certain of having authored the darkness.

It is hardly controversial to say that perceived contiguity enhances perceived authorship, but there is now reason to believe that its less familiar converse is also true: perceived authorship enhances perceived contiguity. Evidence for this hypothesis comes from research on intentional binding, a perceptual illusion in which actions and their effects seem to occur especially close in time (Haggard, Clark, & Kalogeras, 2002). In an experiment based on Libet’s time judgment paradigm (Libet, Gleason, Wright, & Pearl, 1983), participants were asked to press a key when they felt the urge to do so, and an auditory tone was played shortly after they acted. Participants were supposed to judge, in separate blocks, the time of either their keypress or the subsequent tone, by referring to a hand that rotated around a clock face. The main results showed that participants’ judgments of when their action occurred were shifted forward in time (toward the tone), whereas judgments of when the tone occurred were shifted backward (toward the action), relative to judgments made in baseline blocks in which action and tone occurred alone. Critically, these perceptual shifts did not occur when transcranial magnetic stimulation (TMS) induced the participant to make an involuntary keypress, suggesting that voluntary action is needed. Haggard et al. (2002) concluded that the perceived shifts in time result from the mind’s attempt to construct a coherent conscious experience of our own agency, by binding our intentional actions to their effects.

Several experiments have provided additional support for the hypothesis that binding arises when personal authorship for an event is inferred. Some have focused on the “personal” aspect of this hypothesis, showing that binding occurs for one’s own, voluntary actions, but not for involuntary movements (Engbert et al., 2008, Haggard and Clark, 2003) or the actions of others (Engbert et al., 2007, Engbert et al., 2008). Others have focused on the “authorship” aspect, showing that the presence of authorship indicators (Moore, Wegner, & Haggard, 2009) or the provision of control over events (Cravo et al., 2009, Moore et al., 2008) enhances binding (see also Stetson, Cui, Montague, & Eagleman, 2006).

Still, many questions remain about the link between authorship and binding. Previous investigations have not included a corroborating self-report measure of authorship, and without such a measure it is not possible to know for sure whether binding occurs alongside the experience of authorship, increasing and decreasing in response to the same indicators. The lack of a self-report measure has also precluded research into dissociations between what might be considered relatively implicit (binding) and explicit (self-report) measures of authorship (see Synofzik, Vosgerau, & Newen, 2008). One possible dissociation is that people readily report authorship for events that occur several seconds after their actions (Shanks et al., 1989) – and indeed can claim responsibility for an event taking place years after their action – yet binding has been found only for action-event delays lasting a fraction of a second (Haggard et al., 2002, Stetson et al., 2006). Another open question is whether binding occurs for the kinds of actions performed, and events encountered, in everyday life, such as kicking a ball and watching it fly away. Nearly all previous investigations have based their methods on the Libet paradigm, typically asking participants to press a key and judge either the time of their keypress or a subsequent tone, which raises concerns about the external validity of the phenomenon.

We conducted two experiments to address validity concerns and explore the relationship between binding and self-reported authorship. Both experiments employed a novel “push/pull” paradigm that was designed to be relatively naturalistic. Rather than press a key, participants pushed or pulled on a joystick in response to images of everyday objects; rather than hear a tone, participants saw these objects move away or come closer. Unlike a keypress, the acts of pushing and pulling are imbued with bodily significance, implying both an orientation toward whatever is acted upon and an expected outcome of that action. Specifically, pushing corresponds to an avoidance orientation and is undertaken with the expectation that an object will go away, whereas pulling corresponds to an approach orientation and is undertaken with the expectation that an object will come closer (Cacioppo et al., 1993, Chen and Bargh, 1999). In both experiments, we manipulated whether an event was consistent with the participant’s prior action (i.e., whether the object moved in the same direction as the action), both because action-event consistency is an important authorship indicator (Wegner & Sparrow, 2004), and because previous research had not directly examined its effect on binding. In addition to measuring binding, we asked participants to report their feelings of authorship. Our main hypothesis was that action-event consistency would enhance both self-reported authorship and intentional binding – but we were also interested in any differences the two measures might reveal.

Section snippets

Experiment 1

Participants completed a series of trials on which they saw a picture of an everyday object (e.g., an apple) and chose whether to push or to pull on a joystick in response. This action was followed by a brief delay, after which the object appeared to move in a direction either consistent or inconsistent with the action (the event). Participants then estimated the length of the delay between their action and the object’s movement, and these interval estimates served as the measure of binding.

Experiment 2

The present experiment was conducted to verify the results of the first experiment. To provide purer measures of binding and authorship, the experiment was divided into two parts: a block in which only the binding measure was administered, followed by a block in which only the authorship measure was administered. Removing the authorship measure from the first block carried the risk that participants would not consider the degree to which their actions were causing the events to occur, or even

General discussion

The present research tested the hypothesis that intentional binding, in which one’s action and a subsequent event seem to occur especially close in time (Haggard et al., 2002), arises when personal authorship for the event is inferred. Providing support for this hypothesis, two experiments found that an important indicator of authorship – consistency between one’s action and a subsequent event – enhanced both binding and self-reported authorship. Both experiments employed a relatively

Acknowledgments

This research was supported in part by a Harvard University Dissertation Completion Fellowship to the first author and by NIMH Grant MH 49127. We would like to thank research assistants Matthew Benage and Ana Gantman, as well as give special thanks to Verónica López for helping to conduct the research and create the animations that were used.

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