Fig 1.
Types of spontaneous facial self-touch (sFST) during the retention interval.
IN = sFST during acoustic stimulation; OUT = sFST between two sounds. Each retention interval lasted approximately 14 minutes and consisted of 40 sounds and 40 silences. Duration of the sounds and silences varied between 7 and 13 seconds to prevent habituation and anticipation effects.
Fig 2.
Schematic representation of the course of the experiment.
To trigger spontaneous facial self-touch participants had to manually explore (expl) and subsequently remember two relief stimuli for a retention interval (RI) of 14minutes during which aversive sounds were played via loudspeaker. Afterwards they were asked to reproduce (rep) them on a sheet of paper. The process was performed twice with different relief stimuli.
Fig 3.
Sunken relief stimuli and example stimulus.
The participants practiced manual exploration on the example stimulus. Each participant was randomly assigned 4 of the above pictured relief stimuli to be explored during the experiment.
Fig 4.
Schematic representation of the temporal structure of spontaneous facial self-touches (sFST).
Illustrated by C. Maiwald.
Table 1.
Movement times and contact durations of sFST in seconds per experimental phase (within-subjects, n = 30).
Fig 5.
Movement times and contact durations during RI and other experimental phases (within-subjects).
T1 = movement time towards face; T2 = contact duration; T3 = movement time away from face. Paired-samples t-tests revealed longer movement times and contact durations of spontaneous facial self-touch that occurred during the retention interval (RI) than during exploration and reproduction (expl & rep). *p < .05; **p < .01.
Table 2.
Comparison of movement times and contact durations during sounds, between sounds and during other experimental phases.
Fig 6.
Boxplots of temporal aspects of spontaneous facial self-touch during (IN) and between sounds (OUT).
The retention interval consisted of 40 sounds and 40 sound-free periods. Skin contact durations were the longest when facial self-touches were performed between sounds (OUT). T1 = movement time towards face; T2 = contact duration; T3 = movement time away from face; other = sFST during reproduction or exploration; *p < .05.
Table 3.
Frequencies of sFST performed with either one or both hands.
Fig 7.
Self-touch of different face areas during the retention interval.
a) Frequency of sFST per face area. b) Temporal aspects of sFST of different face areas. **p < .01; T1: movement time towards the face; T2: contact duration; T3: movement time away from face. (Face-graphic by C. Maiwald).
Fig 8.
uency of sFST during the retention interval: Both hands were used equally often for ipsi- and contralateral self-touches.
Ipsilateral self-touches occurred significantly more often than contralateral sFST. R = right hand, L = left hand; ipsi = ipsilateral side of face; m = middle axis; contra = contralateral side. (Hand-Icon made by Zlatko Najdenovski from flaticon.com; Face by C. Maiwald).
Table 4.
Frequencies of sFST per hand and face area during (IN) and between (OUT) sounds.
Fig 9.
Two-way analysis of variance of face area and sound on contact duration.
IN = sFST during sounds; OUT = sFST between sounds; The interaction effect and both main effects were significant: contact duration was the longest in the middle axis of the face during silences between the sounds.
Fig 10.
Sensory innervation areas of trigeminal nerve and areas of communicating rami of facial and trigeminal nerve.
Innervation areas: V1 = ophthalmic; V2 = maxillary; V3 = mandibular branch of nervus trigeminus; gray dots: connections of superficial branches of trigeminal nerve and facial nerve [47] (Face by Clker-Free-Vector-Images).