5.3.4.1. Method

Participants. Forty-two undergraduate students participated (mean age of 25 years old, ranging from 19 to 38 years old).

Material and Apparatus. For the emotional induction procedure, 45 photos were selected from the International Affective Picture System. Three emotional categories of picture (positive, neutral, and negative) were classified by a high, medium, or low pleasure score (see Appendix 3). Photographs were displayed on the computer screen at a standard size (23 x 19 cm). A post-experiment questionnaire was developed to determine whether the participants looked attentively at the photos, which photos were remembered in each emotional category, and what emotion was interpreted for each photo set. The other conditions were identical to those in Experiment 1.

Design. A 2(Stroop congruency level) x 3(emotional valence of face: positive, neutral and negative) x 3(emotional induction: positive, neutral and negative) was used. Participants performed a total of 144 trials, divided into three blocks; each block consisted of a set of 15 emotional photographs and 48 trials of colour-naming. The no-face condition was omitted in Experiment 4 for avoiding too many trials in the whole experiment. Other conditions were identical to those in Experiment 1. The order of the three blocks across participants was varied by using standard counterbalancing procedures. The primary prediction of Experiment 4 was the interaction between emotional valence of face and emotional valence of induction.

Procedure. A block consisted of two phases: an emotional induction phase and a test phase. Participants were instructed to look closely at all pictures and told that they would later be required to take a recall test. In the induction phase, each of 15 pictures was displayed for 6 seconds, with a blank interval of one second between them. After the induction phase, the participant was required to perform the same colour-naming task with the emotional face stimulus, as in Experiment 1. After the end of the three blocks, participants completed a post experiment questionnaire. The other conditions were identical to those in Experiment 1.