Table 1 Overview of the interactions used to study human-human interaction to date and the resulting outcomes

1. HHI research has predominantly focused on sensorimotor collaboration, not cooperation

Sensorimotor collaborations

Reed [56, 65], Groten [70], Melendez-Calderon [43], Ikeura [50], Rahman [51], Basdogan [52], Sallnas [53], Gentry [54, 64], van der Wel [55], Feth [66]

Sensorimotor cooperation

Ikeura [60], Galvez [86]

2. The majority of HHI research has used visuomotor tasks with limited degrees-of-freedom

Constrained visuomotor tasks

Melendez-Calderon [43], Ikeura [50], Rahman [51], Basdogan [52], Sallnas [53], Gentry [54, 64], van der Wel [55], Reed [56]

Whole-body non-visuomotor tasks

Galvez [86]

3. In most HHI research, specific roles for each member of a dyad are rarely defined ahead of time

Unassigned roles

Reed [65], Groten [70], Melendez-Calderon [43], Rahman [51], Basdogan [52], Sallnas [53], Gentry [54, 64], van der Wel [55], Reed [56, 65], Feth [66]

Assigned roles

Ikeura [50, 60]

4. Dyads typically perform as well or better than either member of a dyad alone

Superior dyad performance

Reed [65], Gentry [54], Feth [66]

Equivalent individual and dyad performance

van der Wel [55]

5. The addition of haptic feedback improves dyad performance compared to visual feedback alone

Basdogan [52], Sallnas [53], Gentry [64], Groten [67, 71]

6. Members of a dyad apply higher forces than during either of their individual performances

van der Wel [55], Reed [68], Groten [70, 71], Feth [66]

7. Members of a dyad spontaneously assume specific roles, performing portions of a joint motor task

Melendez-Calderon [43], Reed [32, 56]

Starting or ending movement

Reed [32, 68]

Adding or absorbing energy

Feth [66]