Each trial starts with a fixation cross in the centre of the screen. This is presented for 250ms before two images are presented horizontally to the left and right of the cross. The fixation cross remains on the screen to ensure its appearance does not compete for attention (Chanon et al., 2010). The pictures remain on the screen for either 200ms or 500ms depending on the Stimulus Onset Asynchrony (SOA) condition. At picture offset, a small dot appears in the location vacated by one of the images. The dot remains on the screen until the participant responds either left (Z key) or right (M key). After a response is made, the screen containing only the fixation cross appears to signal the start of the next trial.
The task consists of 16 image pairs for neutral trials, and 16 image pairs for smoking and matching non-smoking trials. The smoking and non-smoking images were developed in our lab and 16 image pairs from the IAPS (Lang et al., 2008) were used to create filler neutral trials. The smoking and neutral images can be reused as they come from our project. However, the IAPS images should not be reused without first sourcing the images from the IAPS reference below.
The trial order is randomised for each participant. Each picture pair is presented four times to cover each combination of image (left and right) and dot location (left and right). For each picture pair, this process is repeated for each SOA condition. This procedure is repeated twice and presented in two blocks, creating 384 trials overall with 64 trials in each SOA and trial type condition.
Chanon et al. (2010)
Lang et al. (2008)