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, 2017 (1), nix002
eCollection

Deliberation Period During Easy and Difficult Decisions: Re-Examining Libet's "Veto" Window in a More Ecologically Valid Framework

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Deliberation Period During Easy and Difficult Decisions: Re-Examining Libet's "Veto" Window in a More Ecologically Valid Framework

Eve A Isham et al. Neurosci Conscious.

Abstract

Whether consciousness plays a causal role in cognitive processing remains debated. According to Benjamin Libet, consciousness is needed to deliberate and veto an action that is initiated unconsciously. Libet offered that the deliberation window takes place between the time of conscious intent (W) and action (MR). We further examined this deliberation-veto hypothesis by measuring the length of the temporal window (W-MR) when making easy and difficult choices. If Libet were correct that the W-MR is intended for evaluation and cancelation, we should expect a shorter W-MR for an easy decision since less deliberation is presumably needed. Instead, we observed a less intuitive effect: The W-MR window in the easy trials was longer than the W-MR window in the difficult ones. Our results suggest several interpretations including the idea that consciousness may play a causal role in decision making but not in a straightforward manner as assumed by Libet's veto hypothesis.

Keywords: Libet; agency; decision making; decisional complexity; intention; veto; volition; consciousness.

Figures

Figure 1
Figure 1
(a) An experimental trial begins with the presentation of a statement stimulus and a running clock. At the end of the statement, participants were to decide whether they agreed with it, and to take a mental note of the time in which they felt a decision onset by reading from the clock. Subsequently, they pressed a decision button to indicate their decision, and verbally reported the time of the decision onset and the difficulty rating. Each trial concluded in 9 s. (b). In Experiment 2, participants also made additional presses to indicate additional thoughts they had after having had a decision onset. Experiment 2 trials concluded in 12 s.
Figure 2
Figure 2
(a) Timing of decision (W) and motor response (MR) relative to statement offset (time 0; not shown on graph). On each bar, the gray portion represents the time lapse between statement offset and W (i.e. response time), and the black portion represents the time window between W and MR. Participants experienced a decisional inkling sooner in the easy trials (shorter RT), but waited longer to actually press the button in the easy trials (longer W-MR) compared to the difficult trials. (b) Timing of decision (W) relative to the motor response (time 0). Compared to the difficult trials, participants experienced a decisional inkling sooner but waited longer before pressing the button, resulting in a longer W-MR window in the easy trials compared to the difficult trials.
Figure 3
Figure 3
(a) Timing of decision (W) and motor response (MR) relative to statement offset (time 0; not shown on graph). As in Experiment 1, the gray portion of each bar represents the time lapse between statement offset and W (i.e. response time), and the black portion represents the time window between W and MR. In agreement with Experiment 1, participants experienced a decisional inkling sooner in the easy trials (shorter RT), but waited longer to actually press the button in the easy trials (longer W-MR) compared to the difficult trials. (b) Timing of decision (W) relative to the motor response (time 0). Compared to the difficult trials, participants experienced a decisional inkling sooner but waited longer before pressing the button, resulting in a longer W-MR window in the easy trials compared to the difficult trials.
Figure 4
Figure 4
Dual-task may effectively influence the W-MR window. In a difficult trial, clock reading (Task 2) may be delayed [i.e. longer stimulus onset asynchrony (SOA)], resulting in a late W report and a shorter W-MR.

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