B.1.4.1.2. Apparatus

In this experiment, a cue preceded each search display. In the symbolic condition, the cue was a letter corresponding to the French word for the most relevant size (G or P, for small, or large, respectively) or to the word "neutral" (N, for random condition), presented at fixation. In the perceptual condition, the cue was a closed square of the most probable target size (small or large) or a cross (two lines of 0.57° angle each, for random condition), presented at fixation. The search arrays were the same as in Experiment 1. The letter size was of 0.5° x 0.4° angle (1.10 cd/m²). After a neutral cue, each square had the same 33 % probability to be the target. After a cue indicating the large square, this latter had a high (67 %) probability, whereas both others had an equally low probability (17 %) to be the target. After a cue indicating the small square, this latter had a high (67 %) probability, whereas both others had an equally low probability (17 %) to be the target. Both kinds of cue (symbolic and perceptual) provided identical statistical information about to the target size. All these probabilities were explicitly stated to the participants.