The time-related information about a nocebo treatment can modify its onset of action but not the heart rate variability

INTERVENTION: Randomization 1:1 allocation ratio, computer‐generated random numbers lists with simple randomisation In order to test the nocebo temporal onset, participants perform the cold pressor test (CPT), which is an excellent experimental paradigm to induce a type of pain that mimics the effects of chronic conditions. Participants are asked to resist at the CPT as long as they could until the pain became unbearable (VAS = 100). An inactive cream is applied to the participants’ dorsal and volar left hand. The cream consists of a water‐based gel (KY‐gel Johnson & Johnson) which is presented to participants in a transparent plastic tube. Participants believe that the cream is a powerful hyperalgesic. Temporal information provided varies throughout the three groups: Control: the experimenter explains that the cream is inert, without any effects on pain perception N5: the experimenter explains that the cream is a powerful hyperalgesic which takes effect after 5 minutes N30: the experimenter explains that the cream is a powerful hyperalgesic that takes effect after 30 minutes. After providing written informed consent, participants are seated on a comfortable chair positioned next to the CPT device. The participants perform four CPT tests (familiarisation, baseline, CPT after 10 minutes, CPT after 35 minutes) during which their heart rate is measured. After providing written informed consent, participants are seated on a comfortable chair positioned next to the CPT device. The experiment starts with a 4‐minute heart rate measurement at rest, during which the participant has to breathe naturally and relax. After that, participants are told about the CPT a CONDITION: Nocebo modulation ; Not Applicable PRIMARY OUTCOME: ; The resistance time to the cold pressor test (CPT) measured using a stopwatch at baseline, CPT after 10 minutes, CPT after 35 minutes.; The difference in percentage change of pain tolerance time is calculated as described below:; ?10 = (CPT Test 10’*100)/Baseline CPT‐100; ?35 = (CPT Test 35’*100)/Baseline CPT‐100; INCLUSION CRITERIA: 1. Healthy volunteers recruited from the student population of the VUB and through different social media outlets 2. Aged between 18 and 45 years old SECONDARY OUTCOME: ; 1. Heart rate variability measured using the Polar V800 (Polar Electro Oy, Kempele, Finland) for 4 minutes at the beginning of the trial, 1 minute before each CPT performance and 2 minutes after each CPT performance; 2. Level of anxiety measured using the Beck Anxiety Inventory (BAI) between the familiarisation phase with the CPT and the other test sessions; 3. Motivational systems measured using the Behavioural Avoidance/Inhibition Scale (BIS/BAS) between the familiarisation phase with the CPT and the other test sessions; 4. Fear of pain measured using the Fear of Pain Questionnaire (FAI) between the familiarisation phase with the CPT and the other test sessions; 5. Degree of optimism measured using the Revised Life Oriented Test (LOT‐R) between the familiarisation phase with the CPT and the other test sessions;