Making oneself predictable: reduced temporal variability facilitates joint action coordination

Abstract

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. Identifying coordination strategies contributes to the understanding of the mechanisms involved in real-time coordination.

Fig. 1

Setup and design. Pairs of participants performed a two-choice version of the Simon tasks next to each other, responding to the color of visual stimuli on the left or right side of the screen with a left or right button press. The mapping of stimulus and response side was manipulated as a between-subject factor. In the corresponding mapping group (left panels), stimuli were always congruent (upper left panel) or incongruent (lower left panel) for both coactors. In the non-corresponding mapping group (right panels), coactors had different mappings such that the same stimulus was at the same time congruent for one participant and incongruent for the other participant

Fig. 2

Results of Experiment 1 (synchronous coordination). a Reaction times were less variable in the joint condition than in the individual condition. Error bars display within-subject confidence intervals (Loftus and Masson 1994). b Reaction times were faster in the joint compared with the individual condition. c Zero-order correlations showed that response asynchronies were positively correlated with standard deviation and mean reaction times. Moreover, partial correlations (in brackets) suggest that variability had a direct influence on asynchrony (thick black arrow), whereas speeding supported coordination only indirectly (significance levels: *P < .05; **P < .001)

Fig. 3

Results of Experiment 2 (synchronous coordination). a Reaction times were less variable in the joint intentional condition compared with the individual condition. Mean standard deviation was also reduced in the joint unintentional condition. Error bars display within-subject confidence intervals (Loftus and Masson 1994). b Reaction times were not faster in the joint intentional and unintentional conditions than in the individual condition. c In the joint intentional condition, response asynchronies were positively correlated with standard deviation and mean reaction times as shown by zero-order correlations. Partial correlations (in brackets) support the prediction that only response variability had a direct influence on asynchronies (thick black arrow), whereas speeding supported coordination indirectly (significance levels: *P < .05; **P < .001). c In the joint unintentional condition, only speed was correlated with asynchronies (thick black arrow) as shown by zero-order and partial correlations (in brackets). Variability of responses did not influence how well coactors were coordinated

Fig. 4

Effect of the order of conditions in Experiment 2. a Reduced variability in the joint intentional and joint unintentional conditions was found when participants performed the individual condition first. b Responses were also faster in the joint conditions in participants starting with the individual condition. c Variability was not reduced when participants performed the joint condition first. d Also, the reaction times were not reduced in participants starting with the joint condition. Error bars display within-subject confidence intervals (Loftus and Masson 1994)

Fig. 5

Results of Experiment 3 (sequential coordination). a Leaders’ reaction times were less variable (reduced standard deviation) in the joint condition than in the individual condition. Error bars display within-subject confidence intervals (Loftus and Masson 1994). b Reaction times of the leader were faster in the joint compared with the individual condition. c Zero-order correlations showed that the asynchrony between leaders’ and followers’ responses was positively correlated with the standard deviation and mean reaction times of the leader. Moreover, partial correlations (in brackets) indicate that the leader’s response variability had a direct influence on asynchrony (thick black arrow), whereas speeding supported coordination only indirectly (significance levels: *P < .05; **P < .001)