Page 66 - Demo

Chapter 364StimuliPictures for the three different expression modalities, namely face, body and subtle cues, were taken from existing stimulus databases and edited in Adobe Photoshop (version CC). For the prototypical facial expressions, we selected pictures of 8 identities from the NimStim set of Facial Expressions (Tottenham et al., 2009), displaying happy, angry, sad, fearful and neutral expressions respectively (40 stimuli in total; overall recognition rate in validation studies: M = 82.14% and SD = 5.42%). The bodily expressions were taken from the bodily expressive action stimulus test (BEAST; de Gelder & Van den Stock, 2011) and, similarly, our set encompassed 8 identities displaying happy, angry, sad, fearful and neutral postures each (40 stimuli in total; overall recognition rate in validation studies: M = 94.93% and SD = 2.29%). The backgrounds of the facial and bodily stimuli were cut out and replaced with a uniform grey background (RGB: 145, 145, 145). In addition, grey-scale versions of all body stimuli were created in order to control for effects of clothing colour, and a Gaussian blur was applied to their faces to control for facial expressions. In addition, three subtle facial cue stimuli (blush, dilated pupils and tears) were created by manipulating the neutral expression of each of the eight identities resulting in 24 subtle cue stimuli (for an example, see Fig. 1A). For the stimuli with dilated pupils , the original pupil size in each picture was increased to be clearly visible, on average by 23%. The %u2018tears%u2019 stimuli were made by artificially adding a tear on the actor%u2019s left cheek, increasing the redness of the sclera by making the veins more visible, and adding a reflection and watery blur to the eyes. Lastly, %u2018blush%u2019 stimuli were created by increasing the redness of the cheek region. In total, there were 104 stimuli.ProcedureAfter participants provided informed consent, physiological data acquisition tools were applied, starting with electrodes for skin conductance level (SCL), then electrodes for facial electromyography (EMG) and lastly a skin temperature (SKT) sensor (for more details, see measurements section). In order to allow the signals to reach a stable baseline, a rest period of approximately 10 minutes passed before starting the data collection. In total, participants had to perform three tasks: a passive viewing task (PVT), an emotion labelling task (ELT) and an emotional dot-probe task, of which only the first two will be discussed in the scope of this