Fig 1.
Effect of force on pleasantness ratings for directly experienced, robotic touch to the ventral forearm.
Means ± 95% confidence intervals are shown. Touch delivered at a force of 0.4 N was rated significantly more pleasant than touch delivered at 0.05 N (p = .021) and 1.5 N (p < .001). Touch delivered at 0.05 N was rated significantly more pleasant than touch delivered at 1.5 N (p < .001).
Fig 2.
Effect of velocity on pleasantness ratings for directly experienced robotic touch to the ventral forearm.
Means ± 95% confidence intervals are shown. Touch delivered at 10 cm/s was rated as significantly more pleasant than all other velocities (ps < .001), with 0.3 cm/s touch rated as significantly less pleasant than all other velocities (ps ≤ .021). All pairwise comparisons were significant, apart from the difference between static and 30 cm/s touch (p = .086) and the difference between 1 and 30 cm/s touch (p = .535).
Fig 3.
Interaction effect of location by velocity on vicarious touch ratings.
Means ± 95% confidence intervals are shown. For touch applied to the dorsal hand, static touch (0 cm/s) was not rated as significantly different to CT-optimal (3 cm/s) touch (p = .793). For all other locations, CT-optimal (3 cm/s) touch was rated significantly more pleasant than all other velocities (ps < .001).
Fig 4.
Effect of location on vicarious touch ratings.
Means ± 95% confidence intervals are shown. Pairwise comparisons comparing the ratings for each location to all other locations were all significantly different (ps ≤ .019), except ratings for the dorsal compared to ventral forearm (p = .311).
Fig 5.
Effect of velocity on vicarious touch ratings.
Means ± 95% confidence intervals are shown. Pairwise comparisons identified CT-optimal 3 cm/s touch was rated significantly more positively than CT non-optimal static, 0.5 cm/s and 30 cm/s touch (ts(9826) ≥ 16.45, ps < .001). However, static touch was rated significantly more positively than 0.5 cm/s touch and 30 cm/s touch (ts(9826) ≥ 7.32, ps < .001). Touch at 0.5 cm/s was rated significantly more positively than 30 cm/s touch (t(9826) = 7.24, p < .001).
Fig 6.
Relationship between attitude to intimate touch (AIT, as determined by the Touch Experiences and Attitudes Questionnaire (TEAQ)) and the quadratic velocity terms for 0.4 N touch.
The linear regression line with 95% confidence interval band is shown. More positive attitudes towards intimate touch are related to a more negative quadratic term and therefore steeper inverted U-shaped relationship between touch pleasantness and stroking velocity, indicating greater sensitivity towards CT-targeted touch (p = .014).
Fig 7.
Relationship between perceived stress (as measured by the Perceived Stress Scale (PSS)) and static robotic touch pleasantness ratings.
The linear regression line with 95% confidence interval band is shown. Greater perceived stress was related to reduced static robotic touch pleasantness (p = .002).
Fig 8.
Relationship between attitude to intimate touch (AIT, as determined by the Touch Experiences and Attitudes Questionnaire (TEAQ)) and the quadratic velocity terms for vicarious dorsal forearm touch.
The linear regression line with 95% confidence interval band is shown. More positive attitudes towards intimate touch are related to a more negative quadratic term and therefore a steeper inverted U-shaped relationship between touch pleasantness and stroking velocity, indicating greater sensitivity towards CT-targeted touch (p = .031).
Fig 9.
Relationship between attitude to intimate touch (AIT, as measured by the Touch Experiences and Attitudes Questionnaire (TEAQ)) and vicarious, self-focussed, dorsal hand touch ratings.
The linear regression line with 95% confidence interval band is shown. More positive attitudes to intimate touch are related to more positive static touch ratings (p = .016).