Researchers have also speculated that trypophobic reactions could be perceived as cues to infectious disease, which could be alerts that give one a survival advantage. In a study by Kupfer and Le, trypophobic and non-trypophobic participants showed significant aversion to disease-relevant cluster images, but only trypophobic participants displayed significant aversion to disease-irrelevant cluster images. Martínez-Aguayo et al. stated that, because the reactions could not be attributed to different sensitivity levels or neuroticism differences, Kupfer and Le believe it supports their hypothesis that trypophobia is "an overgeneralized aversion towards cluster stimuli that indicates a parasitic and infectious disease threat".[1] Yamada and Sasaki also propose that trypophobic reactions are due to the imagery's visual similarities to skin diseases.[3]