Material and methods

5.3.1 Participants

Sixty participants were recruited from the undergraduate degree program of the Faculty of Psychology at the University of Lisbon. Participants received course credits for their participation.

77 5.3.2 Tools

5.3.2.1 Experimental apparatus

Pain was induced by a bipolar felt pad electrode (Digitimer, Hertfordshire, England) placed on the left arm, near the wrist (posterior). The electrode, filled with conductive gel, was connected via extension cable to a constant current stimulator (Digitimer, model DS7A; Hertfordshire, England) in the experimenter room. The stimulator had a Bayonet Neill-Concelman connector (BNC) trigger input socket that allowed the connection of a synchronizer (Plux Wireless Biosignals, SA, Lisbon, Portugal). The experimenter’s computer “triggered” the stimulus in the form of a transistor- transistor logic (TTL) trigger pulse, allowing the DS7A to be triggered externally.

5.3.2.2 Social distress manipulation and assessment

The Cyberball procedure was used to induce social distress as demonstrated in Eisenberger et al (2003). Cyberball is a virtual ball tossing game developed by Williams et al. (2000) to manipulate feelings of social rejection. In this procedure, subjects believe they are playing with other participants sitting at other computers else where and connected via an internet network. In fact, however, the other two players are simulated by the software. The Cyberball manipulation comprises three study conditions: (1) In the inclusion condition, participants play with the other ‘players’ and no social distress occurs. There are two exclusion conditions (2) In the overtly excluded condition, at first the other ‘players’ throw the ball to the participant, but then they start tossing the ball only between the two of them and the participant never again receives the ball. (3) In the non- inclusion condition the same situation occurs, but the participant is informed that the other participants are unable to pass the ball to him/her due to technical problems.

The psychological impact of the Cyberball was assessed according to Williams et al. (2000), with Belonging (e.g. “I felt disconnected”), Self-esteem (e.g. “I felt liked”), Meaningful Existence (e.g. “I felt meaningless"), Control (e.g. “I felt I had control over the course of the game”) subscales, with each item answered on a 5-point scale ranging from

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“Not at all” to “Extremely”. The total score is obtained from the average of subscales scores. This measure was used according to previous studies (Eisenberger et al., 2003; Eisenberger et al., 2006): Higher ratings indicate that the participants felt their psychological needs threatened to a greater degree and, as such, felt more socially distressed after the game. At the end of the study, subjects were directly asked whether they believed that they were playing with players from other labs.

5.3.2.3 Pain Stimulation Pre-Cyberball

Familiarization trial

Participants were initially exposed to three stimuli, to familiarize them with the procedure and with the pain and unpleasantness ratings. The participant rated each stimuli by moving sliders controlled by the mouse in two computerized visual analogue scales (Co-VAS): pain intensity and pain unpleasantness. The scales aimed to assess sensory and emotional components of pain (respectively). On the first slider, they rated the perceived pain, ranging from 0, corresponding to “not painful at all” to 10, corresponding to “the worst pain one can imagine”. On the second slider, they rated unpleasantness, ranging from 0, “not unpleasant at all” to 10, “the most unpleasant one can imagine”.

Calibration

An ascending sequence, started with an intensity of 40 mA and augmented in 20 mA steps, was administered to individually adjust stimulation intensity. Stimuli duration was 0.2 ms with inter-stimuli intervals randomly distributed between 15 and 20 seconds. The sequence was terminated when participants rated their pain as 6. The lowest stimulus intensity that was rated as painful was considered as the pain (or unpleasantness) threshold.

A second stimulation sequence was constructed based on the ascending sequence results. This was an 11-stimuli, random sequence calibrated so as to deliver equally- spaced intensity stimuli between the threshold (intensity rated as 1) and the intensity rated as 6. These intensities were extrapolated for each participant to correspond a 0 to

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10 scale with 11 stimulation intensities using the following formula- threshold stimulation intensity + 0.1*( pain 6 stimulation intensity - threshold stimulation intensity ) (this is an example for calculating intensity of 1, 0.2 instead of 0.1 was used to calculate ‘pain 2’ intensity and so forth). Participant’s responses to the second stimulation sequence were used for constructing the post Cyberball stimulation sequence.

5.3.2.4 Pain stimulation Post-Cyberball

At the end of the game, participants received 3 stimuli calibrated for targeting a pain intensity of 4. This was done by using a simple linear regression carried out for each participant individually immediately after the 11-stimuli sequence, yielding the required stimulus intensity for the next stage of the experimental procedure. The regression formula used was as follows: = (4-a)/b (a is the mean of the participants’ intensities ratings in response to the 11 stimuli minus b multiplied by the mean of the intensities, b is the mean of the ∆x∆y divided by ∆x2). These three stimuli had the same duration and interval as in the previous sequence. In response to each stimulus, participants rated pain intensity and unpleasantness by using the Co-VAS. Post Cyberball stimulation pain and unpleasantness were calculated as the mean response to these three stimuli.

5.3.3 Questionnaires

In addition to participant demographic information, the Experiences in Close Relationships questionnaire (ECR) and the Portuguese version of the Big Five Inventory (BFI) questionnaires were completed prior to the Cyberball manipulation.

Before the Cyberball manipulation, close relationship style was assessed by using the Experiences in Close Relationships questionnaire (ECR) (Brennan et al., 1998), which measures the two fundamental dimensions in adult attachment style: Preoccupation and Avoidance. It contains 36 items, rated on a 7-point scale, ranging from 1 “strongly disagree” to 7 “strongly agree”, and a central point of 4 “neutral/mix”. The Portuguese

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version of this questionnaire was developed by Moreira et al. (2006) and has been shown to have adequate psychometric properties.

At the end of the procedure, subjects completed the neuroticism scale of the Portuguese version of the Big Five Inventory (BFI) (John and Srivastava, 1999) to confirm that the impact of the Cyberball manipulation was not confounded by an individual tendency to appraise situations as threatening. This scale consisted of 7 items rated on a 5-point scale ranging from 1 for “strongly disagree” to 5 for “strongly agree”. The Portuguese version was developed and validated by Moreira (2002).

5.3.4 Procedure

The study was approved by the Ethics and Deontology Commission of the Faculty of Psychology of University of Lisbon. As a first step of the study, on the morning of the experiment, participants completed online the demographic and Pre-Cyberball questionnaires sent via e-mail. Later on the same day, participants came to the laboratory for the second part of the study. Informed consent was obtained from all subjects prior to the beginning of each part of the study. Participants were told that the study aim was to assess the impact of working with video screens on the perception of pain. The participants were seated in a small room in front of a computer screen with the electrode attached to their wrist. This room was contiguous to the experimenter room but was separated by two doors so the experimenter could not see or interact with subjects.

Following the pre-Cyberball pain stimulation, each participant was randomly assigned to one of the three Cyberball conditions. Assignment was automatically done by the computer so that the experimenter did not know to which study condition subjects were assigned to until the beginning of the Cyberball game. In the non-inclusion condition, the experimenter entered the participants’ room to inform about ‘technical problems’ and ask the participant to continue concentrating on the game. At the end of the game, post-Cyberball pain stimulation was administered and questionnaires were completed. After completion of the entire procedure, subjects were fully informed about the actual aims of the study and the rejection manipulation.

81 5.3.5 Statistical analysis

Analyses were conducted by the SPSS for Windows Version 19 statistical package (SPSS, Inc., Chicago, IL) (IBM, 2010). Chi Square and analysis of variance (ANOVA) tests were used to assess differences in demographic characteristics between study groups. ANOVA was utilized to assess differences between study conditions in baseline pain and unpleasantness, psychological characteristics, social distress and post-Cyberball pain and unpleasantness. Pearson’s correlation was used to study relations between post- Cyberball pain and unpleasantness, social distress and psychological characteristics. The one sample t-test was utilized to assess differences between post-Cyberball pain intensity and unpleasantness and the predicted value of 4. Values are presented as means and standard deviations (SD). Results of all analyses were considered significant at the p < 0.05 level.