Helping the waiter to hold his tray: Rigid haptic linkage promotes inter-personal motor coordination.

Dardo N Ferreiro,Bahador Bahrami,Chris D Frith

doi:10.1177/17470218211009082

Abstract

When a glass is lifted from a tray, there is a challenge for the waiter. He must quickly compensate for the reduction in the weight of the tray to keep it balanced. This compensation is easily achieved if the waiter lifts the glass himself. Because he has, himself, initiated the action, he can predict the timing and the magnitude of the perturbation of the tray and respond (via the holding hand) accordingly. In this study, we examined coordination when either one or two people hold the tray while either one of them or a third person removes the glass. Our results show that there is exquisite coordination between the two people holding the tray. We suggest that this coordination depends upon the haptic link provided by the rigid platform that both people are holding. We conclude that the guest at a reception should not lift his drink from the waiter’s tray until they have the waiter’s attention but, if too thirsty to wait, should lend a hand holding the tray.

Highlights

The thirsty guest at reception should not lift his drink from the waiter’s tray
Extending the predictive control theory to interpersonal coordination, we examined whether this reduction was as great when the two hands belonged to different people (Hypothesis 2)
In an interactive experiment conducted in the course of a public, science-engagement event at Tate Modern Museum in London, we replicate the earlier finding that there is less disruption in the stability of a tray when the person who lifts a beaker off the tray is the one holding the tray

Summary

Introduction

The thirsty guest at reception should not lift his drink from the waiter’s tray. He should wait for the waiter to hand it to him. When the glass is lifted from the tray, there is a challenge for the waiter He must quickly compensate for the reduction in the weight of the tray (i.e., generate a downwards movement) to keep the tray balanced. This compensation is much more achieved if the waiter lifts the glass himself. The compensatory response to the removal of the glass from the tray will be initiated earlier and, second, the amplitude of the perturbation will be smaller This is an example of bi-manual coordination between the hand doing the lifting and the hand holding the tray. Presenting a tone that signals the onset of lifting does not

Methods

Results

Conclusion