Abstract:

Over the long course of evolution, in order to cope with the threat of pathogens, both animals and humans have evolved complex disease defense mechanisms, one of which is known as the behavioral immune system. The behavioral immune system is a complex suite of cognitive, affective, and behavioral mechanisms that ultimately help prevent pathogen transmission in the face of recurrent infectious disease threats. It functions by detecting threat-relevant cues in the environment and activating disgust-related responses aimed at diminishing those threats. However, in modern times, with advanced medical technology, the behavioral immune system may not always be beneficial to human disease control behaviors. Previous studies have found that, the social strategies that are designed to avoid infection in ancient times may lead to more serious health problems (e.g., the damage to the cardiovascular system) in modern society. These studies suggest that the behavioral immune system may be evolutionary mismatch in the modern and complex medical environment, which may have a negative impact on our medical-seeking behavior. Therefore, we hypothesized that in modern society, the activation of behavioral immune system will affect individuals' medical-seeking tendency, making individuals display more negative attitudes towards health-care and become more likely to delay their medical-seeking.
This hypothesis was systematically tested by five different studies. In these studies, we used a well-validated medical-seeking attitude questionnaire and a computerized patient delay task to measure the individuals' medical-seeking tendency. Specifically, in Study 1A (223 participants) and Study 2A (218 participants), we investigated the relationship between trait activation level of behavioral immune system and individuals' medical-seeking tendency by employing the scales of Disgust Scale-Revised Chinese and Perceived Vulnerability to Diseases. In Study 1B (198 participants) and Study 2B (174 participants), we situationally activated the behavioral immune system by asking the participants to watch disease-salient primes in order to investigate the effects of external disease cues on the medical-seeking tendency. In Study 3, we investigated that whether the effects of the activation of behavioral immune system on the medical-seeking attitude and tendency were mediated by the perception of the risk of hospital infection.
The results showed that: 1) core disgust (M = 27.83, SD = 6.36) negatively predicted the attitude of participants toward medical-seeking (M = 26.64, SD = 3.25), β = −0.20, SE = 0.09, t (203) = −2.27, p = 0.03, 95% CI = [−0.37, −0.03] ; 2) core disgust (M = 27.59, SD = 6.35) positively predicted the tendency of participants to delay medical-seeking (M = 6.46, SD = 5.88), β = 0.25，SE = 0.10, t (196) = 2.57, p = 0.01, 95% CI = [0.06, 0.43]; 3) situationally activating the behavioral immune system significantly affected the attitude of participants toward medical-seeking and the tendency of participants to delay medical-seeking, participants were found to be more likely to have a negative attitude toward medical-seeking (disease-salient: M = 26.96, SD = 3.63; control: M=28.05, SD=3.07; t(196) = −2.1, p = 0.04, d = 0.3, 95% CI = [−2.11, −0.07]) and delay their medical-seeking (disease-salient: M = 8.23, SD = 6.66; control: M = 6.12, SD = 5.79; t(172) = 2.23, p = 0.03, d = 0.34, 95% CI = [0.24, 3.98]) after watching the disease-salient primes; 4) the perception of the risk of hospital infection mediated the relationship between the activation of behavioral immune system and medical-seeking attitude and tendency, participants who had higher core disgust or received disease-salient primes were more likely to perceive the medical-seeking situations as infectious, which subsequently led the participants to adopt more negative attitude toward medical-seeking (indirect effect of disease prime: β = −0.03, SE = 0.02, 95% CI = [−0.08, −0.001]; indirect effect of core disgust: β = −0.04, SE = 0.03, 95% CI = [−0.11, −0.002]) and to display stronger patient-delay tendency (indirect effect of disease prime: β = 0.03, SE = 0.02, 95% CI = [0.004, 0.08]; indirect effect of core disgust: β = 0.05, SE = 0.04, 95% CI = [0.01, 0.17]) (see Figure 1).
These results support our hypothesis, suggesting that the ancient behavioral immune system may have a negative effect on the medical-seeking behavior of contemporary society. These results are consistent with the evolutionary mismatch hypothesis and provide a new theoretical perspective for the further understanding of the medical-seeking behavior of modern human.

Key words: behavioral immune system, disgust, medical-seeking behavior, patient delay, evolutionary mismatch hypothesis