(40–48, mean 43.7, SD 2.7). Extreme (low and high) scorers on the TAS-20 scale were chosen in line with previous studies [26,27]. Individuals with average scores were additionally included in order to ensure a broad and continuous spectrum of alexithymia scores on the cognitive dimension of the Bermond-Vorst Alexithymia Questionnaire (BVAQ), which correlates to approx. 80% with the TAS-20 [8], and to increase the probability of a wide range of scores on the affective alexithymia dimension, which the BVAQ assesses in addition. Scores on the affective and the cognitive dimension of the BVAQ, which was to be filled out directly after the EEG session were then used in correlation analyses to test whether the two alexithymia dimensions show a differential impact on the attended and unattended processing of emotional prosody. All participants were healthy female native speakers of Dutch (age range 18–25 years), with no neurological or psychiatric disorders in present or past, normal hearing, and normal or corrected-to-normal vision. Participants received J 20 for their participation in the study. Ethics statement The Medical Ethical Committee of the University Medical Center Groningen approved the experimental protocol, and all participants gave written informed consent prior to the study. The study was conducted in accordance with the Declaration of Helsinki. Toronto Alexithymia Scale (TAS-20) The TAS-20 is the most widely used measure of alexithymia with a demonstrated validity, reliability, and stability [67,68]. A validated Dutch translation of the scale was used for the present study. The scale consists of 20 self-report items rated on a 5-point Likert scale (1: strongly disagree, 5: strongly agree), with five negatively keyed items. The TAS-20 comprises three subscales assessing alexithymia at a cognitive level: (1) difficulty identifying feelings (e.g., ‘‘I often don’t know why I’m angry’’), (2) difficulty describing feelings (e.g., ‘‘I find it hard to describe how I feel about people’’), and (3) externally oriented thinking (e.g., ‘‘I prefer talking to people about their daily activities rather than their feelings’’). Possible scores range from 20 to 100, higher scores indicate higher degrees of alexithymia. Bermond-Vorst Alexithymia Questionnaire (BVAQ) The BVAQ is a 40-item self-report scale, which consists of five subscales with eight items per scale [8]. The five subscales are: 1) (Difficulty) Verbalizing one’s own emotional states, (2) (Difficulty) Identifying the nature of one’s own emotions, (3) (Difficulty) Analyzing one’s own emotional states, (4) (Difficulty) Fantasizing: the degree to which someone is inclined to imagine, day-dream, etc., and (5) (Difficulty) Emotionalizing: the degree to which someone is emotionally aroused by emotion-inducing events. Answers are scored on a 5-point Likert scale (1 = certainly does not apply to me, 5 = certainly applies to me). The five-subscale structure of the BVAQ corresponds to the original description of alexithymia by Nemiah and Sifneos [7,69], who had defined the alexithymia concept by the following features: reduced capacities in emotionalizing, fantasizing, identifying emotions, verbalizing emotions, and pense´ ope´ratoire (externally oriented thinking) or analyzing emotions. The three subscales identifying, analyzing, and verbalizing feelings assess the cognitive alexithymia dimension. There is substantial overlap between the cognitive subscales of the BVAQ and the TAS-20, reflected in a high correlation between the sum scores on these three BVAQ subscales and the TAS-20 sum score (r = .80) [8,70], indicating The Sound of Feelings that these scales measure the same features [8]. The two BVAQ subscales emotionalizing and fantasizing assess the affective dimension of alexithymia. The validity of this two-factor structure of the BVAQ with an affective versus a cognitive alexithymia dimension has been demonstrated by factor-analyses in six languages and seven populations [71–73]. High scores on the cognitive alexithymia dimension indicate low abilities to identify, analyze, and verbalize feelings. High scores on the affective alexithymia dimension indicate low abilities to emotionalize and fantasize. Materials An auditory oddball paradigm with 80% standards and 20% deviants was created for the present study. Nonsense syllables (baba, dada, gaga) spoken in neutral, happy, angry, sad, and disgusted intonation in low (e.g., a bit sad) and high (e.g., very angry) intensity constituted the stimuli of this paradigm. Nonsense syllables were chosen in order to exclude interference by semantic processing, enabling us to specifically measure electrophysiological responses to variations in emotional prosody. The syllables ‘‘baba’’, ‘‘dada’’, ‘‘gaga’’ were chosen because they have the same consonant (C) – vowel (V) structure (CVCV), employ the same vowel and contain only voiced consonants, keeping acoustic features of the stimuli constant across conditions. The stimuli were recorded with the help of a semiprofessional actress, who pronounced the syllables in neutral, happy, angry, sad, and disgusted prosody with low and high emotional intensity. The recorded stimuli were cut to a length of approximately 600 ms and amplitude normalized using the Praat speech processing software [74]. The procedure amplified every stimulus item such that the digitalized sample with the maximum amplitude was set at the maximum positive or negative value of the converter range, and all other samples were scaled proportionally. As a result, all stimuli had about equal volume. The stimuli were validated in two pilot studies with 13 independent raters each. The raters were asked to indicate which emotion was conveyed by the respective stimulus (neutral, happy, angry, sad, disgusted, other emotion) and which emotional intensity the stimuli were spoken in (low intensity, high intensity, other). Only stimuli that were rated by 10 out of 13 raters to convey the correct emotion in the intended intensity were included in the study. The oddball paradigm was presented in E-Prime version 1.2 [75] with an interstimulus interval of 600 ms in task 1 (passive task, no response required) and with an interstimulus interval of 1000 ms in task 2 (active task, response required) in order to give participants a sufficient time window for their responses. Each task was initiated by a habituation phase consisting of 20 standards and was presented in a pseudo-randomized manner (different for each participant) with the constraint of two deviants never occurring in succession. The probability of a deviant to occur was the same (20%) in task 1 and 2. Procedure EEG activity was recorded from 64 tin electrodes mounted in an elastic electro cap organized according to the international 10/ 20 system. EEG data were recorded with a linked mastoid physical reference and were re-referenced by using an average reference. Electrooculogram (EOG) was recorded for artefact rejection purposes from electrodes placed on the supraorbital and ridges of the left eye. The ground electrode was applied to the sternum. Impedance of all electrodes was kept below 5 kV for each participant. EEG was continuously recorded with a sampling rate PLoS ONE | www.plosone.org 4 May 2012 | Volume 7 | Issue 5 | e36951