Page 148 - Demo

Chapter 5146practice (four trials). Each trial of the heartbeat discrimination task started with the visual presentation of numbers counting down from 3 for 3s and a short break (depending on the delay condition), after which participants were presented the five tones via headphones and no visual input (blank grey screen). Once all five tones were played, a question screen appeared asking the participants to judge whether the tones were %u201cin sync%u201d or %u201cout of sync%u201d with their heartbeats by key press. On a second screen, they had to indicate the confidence in their decision on a visual analogue scale from %u201ctotal guess/no heartbeat awareness%u201d to %u201ccomplete confidence/full perception of heartbeat%u201d. Integer values ranged from 0-100 but were not visible to the participant. All judgments were made in a self-paced manner. Participants completed 60 trials of the heartbeat discrimination task in total (30 per delay condition). Once the task was completed, the ECG electrodes were removed from the participants%u2019 bodies, and they filled in the questionnaires (see Measurements section) in a randomized order after providing demographical information regarding their age, gender, and nationality. MeasurementsFacial electromyography (fEMG).We used facial electromyography (fEMG) as technique to derive mimicry of the presented emotional expressions. Following the guidelines of Fridlund and Cacioppo (1986), we placed a reusable 4 mm Ag/AgCl surface electrode as a ground electrode on the top of the participants%u2019 foreheads, two electrodes of the same type over the Corrugator Supercilii region (referred to as %u201ccorrugator%u201d hereafter) above the participants%u2019 left eyebrows, and two electrodes over the Zygomaticus Major region (referred to as %u201czygomaticus%u201d hereafter), that is on the participants%u2019 left cheeks. Expressions of sadness, fear and anger are typically associated with increased activations of the corrugator whereas happiness expressions are associated with a decreased activation (i.e., a relaxation) compared to neutral expressions (e.g., Folz et al., 2022; K%u00fcnecke et al., 2014). Additionally, increased activation over the zygomaticus region typically occurs when happiness is expressed. Thus, facial mimicry of the presented expressions should result in similar muscle activations. The fEMG signal was recorded at a sampling rate of 1000 Hz, using a Biopac MP150 system (see Supplemental Materials for details on the data recording and preprocessing). For each trial, separate epochs were defined for the first 500ms of each video with a neutral expression (as baseline) and the 1.5s in which the emotional expression was shown (as response). Based on an automated detection of extreme values as well as manual coding, 41 trials