 Furthermore, by testing alpha amylase levels, scientists noticed a difference in reactivity behavior among individuals with previous experience in a similar situation.While saliva testing has the promise of becoming a valuable and more widely used tool in psychological research in the future, there are also some disadvantages to the method that must be kept in mind, including the cost of collecting and processing the samples and the reliability of the measure itself.There is a substantial amount of both within-person and between-person variability in cortisol levels that must be taken into account when drawing conclusions from studies.