Abstract: Studies have found that fear-relevant snakes can be detected rapidly during visual search. In this study, by comparing snakes and lizards, which also belong to reptiles but have no threat to human in evolution, four experiments were conducted to explore whether snakes would be detected rapidly. Eye tracking technique was used in visual search tasks to record participants' visual search process. In experiment 1, a series of 3×3 matrices of eight colored photographs of snakes or lizards were presented on the screen, without stimulus in the middle. Participants were asked to find out the target (snake) among seven distractors (lizards) and vice versa. Experiment 2 used gray-scale and line-drawing pictures to further investigate snake's low-level perceptual features played in attention detection. To balance the impact of different distractors in experiment 1 and 2, another 24 participants were requested to detect snake or lizard among the uniform distractors (flowers or frogs) in experiment 3. To improve the ecological validity, snakes' and lizards' photos with natural scenes were used in experiment 4. The results of reaction time and eye-movements in experiment 1 indicate that when searching for lizards, attention can be attracted more quickly to targets. Experiment 2 to 4 replicated the key finding of experiment 1. Moreover, awareness of the targets can be promoted with the color and the texture of the lizards and the snakes. The similarities of targets and distractors will hinder the search to the targets. In conclusion, attentional biases are not always specific to snakes, the nature of animal and the perceptual features of the target can influence the fear-related stimuli detection.

Key words: fear-relevant stimuli, snakes, lizards, eye-movements, attention detection