Martínez-Aguayo et al. described trypophobia as usually involving "an intense and disproportionate fear towards holes, repetitive patterns, protrusions, etc., and, in general, images that present high-contrast energy at low and midrange spatial frequencies."[1] Cole and Wilkins also stated the imagery has high spatial frequency with a greater energy at midrange.[2][3] Whether together or separate, it appears that low and midrange spatial frequencies are necessary for inducing trypophobic reactions. Based on the imagery's visual cues, An Trong Dinh Le, Cole and Wilkins developed a symptom questionnaire that they believe can be used to identify trypophobia.[3]