Computational protocol: Neural measures of the role of affective prosody in empathy for pain

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Protocol publication

[…] Prior to data collection, we aimed to include 15–20 participants in the ERP analyses because it is suggested to be an appropriate sample in this field,. Data were collected from twenty-seven volunteers (10 males) from the University of Padova. Data from ten participants were discarded from analyses due to excessive electrophysiological artifacts, resulting in a final sample of seventeen participants (5 males; mean age: 24.29 years, SD = 3.72; three left-handed). By using G*Power 3.1 for a 3 × 2 × 2 × 2 × 2 × 2 repeated measures design, we calculated that for 95% of power given the smallest effect size we observed, 14 was an adequate sample size. Analyses were conducted only after data collection was complete. All participants reported normal or corrected-to-normal vision, normal hearing and no history of neurological disorders. Written informed consent was obtained from all participants. The experiment was performed in accordance with relevant guidelines and regulations and the protocol was approved by the Ethical Committee of University of Padova. [...] Stimuli were sixteen Caucasian male faces, with either a neutral or painful expression as the perceptual cue (pre-verbal domain) and sixteen utterances, with either unintelligible or intelligible emotional content as the semantic cue (verbal domain). The face stimuli were scaled using an image-processing software to fit in 2.9° × 3.6° (width x height) rectangle from a viewing distance of approximately 70 cm.The sentences were uttered by a professional Italian actor and presented by a central speaker at an average value of 52.5 dB. Eight utterances were in participants’ mother-tongue (i.e., Italian) and each of them described a painful situation reported in first-person. Eight utterances were unintelligible (i.e., fictional language). Critically, each sentence was uttered with both neutral and painful prosody (i.e., prosodic cue). The Italian utterances were comparable for syntactic complexity, i.e., noun + verbal phrase (e.g., “I hurt myself with a knife”). The utterances in a fictional language were paired to Italian utterances for length and prosody.To confirm that intelligibility did not affect prosody and vice versa, we tested 20 subjects for a rating task. In two separate blocks, subjects were asked to report (within a 7 points Likert scale) the pain intensity and how much the utterances were conceptually understandable (counterbalanced). We found that there was no significant difference in the pain rating with regard to the prosody (i.e., the tone of the voice) between intelligible and unintelligible utterances (t = 1.59, p = 0.11). Further, there was no significant difference in the intelligibility of the sentences between painful and non-painful prosody (t = −1.01, p = 0.31). Finally, we tested whether the painful prosody was actually perceived more intense than the neutral one, finding a significant difference (t = −54.38, p < 0.001).Participants were exposed to an orthogonal combination of the 16 faces, and the 16 sentences uttered with both neutral and painful prosody. Stimuli were presented using E-prime on a 17-in cathode ray tube monitor with 600 × 800 of resolution and 75 Hz of refreshing rate. […]

Pipeline specifications

Software tools G*Power, E-Prime
Applications Miscellaneous, Neuropsychology analysis
Organisms Homo sapiens