Experimental procedure
The experimental sessions took place in the afternoon, between 3 and 5
p.m., at least 3 hours after the last meal and caffeine containing
beverages intake, in a sound and light attenuated, temperature
controlled (22°C) room. Alcohol consumption was prohibited during the
preceding 24 hours. On the day of the experimental session, all
participants completed the Tellegen Absorption Scale (TAS, Tellegen &
Atkinson, 1974; Tellegen, 1981) whose score indicates the proneness to
be deeply absorbed in mental activities (range: 1-34). They were also
interviewed about the last night sleep satisfaction (range: 0-10) and
were invited to sit in an armchair with their head, legs and arms
supported, and prepared for EEG recording. Finally, they were informed
that every instruction will be given to them by the same experimenter
sitting nearby and that at a certain point they will have to listen to a
pre-recorded voice (SHSS, A induction modified owing to the direct
request to close eyes in R). The experimental session consisted of open
eyes baseline (B, 3 min), closed eyes relaxation (R, 3 min), hypnotic
induction modified from the SHSS, A (IND, divided into IND1 and IND2, 3
min each), neutral hypnosis (NH, 3 min), Post (post hypnosis, 3 min). At
the end of the session participants were invited to score the degree of
change in the state of consciousness experienced during the session
(range: 0-10). None of the participants showed EEG sleep episodes.