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Snakes and spiders grab our attention and grab it even faster if we're phobic, a sign that perception evolved

American Psychological Association

Swedish studies show that we can spot snakes in the grass faster than harmless objects

WASHINGTON -- It's long been thought that the common phobias of snakes and spiders are reminders of homo sapiens' primal past. Now new studies suggest that human perception evolved to accurately and efficiently spot these environmental threats. The research appears in the September issue of the Journal of Experimental Psychology: General, published by the American Psychological Association (APA).

Psychologists Arne Öhman, Ph.D., Anders Flykt, Ph.D. and Francisco Esteves, Ph.D., all then with the Karolinska Institute and Hospital in Stockholm, conducted three studies in which subjects searched for fear-relevant pictures (images of snakes or spiders) in arrays of fear-irrelevant pictures (images of flowers or mushrooms) and vice versa. A statistically significant number of people (the first two studies used 25 and 30 subjects) found the snakes or spiders more quickly than the harmless objects. Also, they found them faster no matter where they were in the array or how many distractors were present, which suggested that they "popped out" from the display to be automatically detected rather than that they had to be actively looked for.

In a third experiment involving 130 subjects, the researchers learned that people who were phobic about snakes or spiders (according to a questionnaire) found their specific feared objects even faster than did the other, non-phobic subjects. Thus, the authors conclude, evolutionarily relevant threatening stimuli pull the attention of sensitized individuals even faster, an emotion-attention interaction that would help them avoid their feared objects more effectively.

The findings supported the authors' hypotheses, which they developed in line with findings about angry faces (another fear-relevant stimulus) and the efficient capture of attention. Previous studies had researched the automatic processing of evolutionarily fear-relevant stimuli outside of awareness. Öhman et al. advanced the research by assessing the pre-attentive selection of significant stimuli, to learn about perceptual processes that automatically scan and analyze the perceptual field.

These findings suggest that humans are predisposed to preferentially direct attention toward potentially threatening animal stimuli, that we do it accurately and efficiently, and that the extra-fearful have a heightened attentiveness to the feared object (though they are less accurate). In short, potential threats grab our attention, which has surely helped us to survive. The authors say their findings not only support the evolutionary hypothesis, but also more specifically suggest a default attentional setting in humans that automatically makes them focus their attention on evolutionarily fear-relevant stimuli.


Article: "Emotion Drives Attention: Detecting the Snake in the Grass," Arne Öhman, Anders Flykt and Francisco Esteves, Karolinska Institute, Stockholm, Sweden; Journal of Experimental Psychology - General, Vol. 130, No. 3.

Arne Öhman can be reached by email at He is with the Section of Psychology, Department of Clinical Neuroscience, Karolinska Institute and Hospital, Z6, S-171 76 Stockholm, Sweden. His telephone number is 46 8 325933.

Full text of the article is available from the APA Public Affairs Office and at

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 155,000 researchers, educators, clinicians, consultants and students. Through its divisions in 53 divisions of psychology and affiliations with 60 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

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