Procedures

2.3.1.1 Stimuli and Materials

The emotional context pictures were selected from the International Affective Picture System (IAPS) (Van Lange, 2008) and the picture repertoire used in a previous study (Rameson et al., 2011). All the pictures were subdivided into 16 sets according to their contexts and reevaluated subjective empathy valance, arousal level and emotional valance in our study. The facial expression pictures were selected from 12 (6 men and 6 female) actors in Taiwan emotional standard stimuli database (Farnand et al., 2009) . One happy face and one sad face expression were chosen form each actor.

The 12 double-character emotional words (៿኷ǵඍ৹ǵࢲΚǵݒ഻ǵ៿഻ǵ౏זǵ ൿኌǵኁ໾ǵݪ഼ǵൿࠉǵधඊǵ໾Ј) were drawn from the emotional standard Chinese phrase database developed by Lee et al (Lee & Lee, 2011). There were no significant differences between arousal level, concreteness, familiarity, frequency and stoke count in chosen words.

2.3.1.2 Tasks

Emotional Stroop

A typical trial of Emotional Stroop started with an emotional (or neutral) context picture presented for 4 sec. One second after the offset of the emotional context picture, a picture of a face paired with a double-character word was presented and last until participants made responses. The two characters were displayed at the cheek level so that they would not cover the eyes of faces. The face could be either a happy or a sad facial expression, and the double-character word could describe either a positive or a negative emotion. The combination of face-word pairs was

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pseudorandomly presented in three different kinds of trial types: congruent (Con) (happy face with positive words or sad face with negative words), negative words with happy face incongruent (NWHF) and positive words with sad face incongruent (PWSF) trial types (see Figure 1) (Hofelich & Preston, 2012; Preston & Stansfield, 2008; Rameson et al., 2011). Participants were instructed to press one key for happy face and another key for sad face as soon and accurate as possible. After the response, there would be a feedback signal (500 ms) with a green square around the face picture for correct responses and a red square for incorrect responses. The Emotional Stroop effect was defined as longer reaction times for the incongruent trials than the congruent trials.

In the current experiment, participants performed emotional Stroop task under 5 different empathy contexts including neutral viewing condition, medical cognitive interference condition, medical empathy induction condition, non-medical cognitive interference condition and non-medical empathy induction condition. There were four blocks for each empathy context with each block contained six pictures belonging to a single emotional context. To prevent the emotional Stroop task of neutral viewing condition from interference by other EI and CI conditions, the neutral viewing condition was presented first and then the other 4 conditions would show in random order. For any medical condition, we used pictures with contexts that health care professionals might encounter in their daily works, such as “This person is suffering from a serious disease” or “This person's father was just taken to the hospital due to a serious accident”. On the other hand, for any non-medical condition, we used pictures with contexts that had nothing to do with health care, such as “This person just lost a career-changing sporting event” or “This person was just fired from a job they really need”. Participants were informed that all emotional context pictures were selected from newspaper, magazines,

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blogs and on-line stories which depict real events.

Subjective Evaluation of Induced Empathy, Valence and Arousal Levels of Emotional Pictures

After completing all Emotional Stroop experiments, participants would view all the emotional context pictures again with short presentation time (one sec/picture) and rate their subjective empathy levels for all pictures. They were required to answer two questions based on the experience they had when they saw the image: 1. How much concern you felt for the person (e.g., sympathetic, compassionate, understand the situations, and moved their feelings), 2. How much disturbance did you experience when you saw the picture (i.e., alarmed, grieved, and upset) (Rameson et al., 2011; Toi

& Batson, 1982)!with a Likert scale from one (not at all) to seven (very much). We hypothesized that participants would show higher subjective empathy and distress levels for the emotional contents of pictures in EI condition than in CI condition. In addition, to rule out the possibilities that any observed Emotional Stroop effect differences were simply caused by differences in arousal and valence levels of the emotional pictures between different conditions, participants were required to view 24 images randomly presented for each person, and to rate the valence and arousal level on the scale from one (valance: negative, arousal: calm) to nine (valance: positive, arousal: excited) for later statistical comparison(Bradley & Lang, 2007; Lang, 1980).

Psychometric Evaluation of Empathy

After participants completed all experiments, they were additionally required to fill up two empathy questionnaires in Chinese version: the Empathy Quotient (EQ) (Baron-Cohen & Wheelwright, 2004) and the Interpersonal Reactivity Index (IRI) (Davis, 1980; Siu, 2005). The main reason to keep questionnaires for the last step was

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to minimize any possibility of social expectation biasing effects caused by participants knowing about the true purpose of the current study.