Humans love certainty and familiarity. One such example for it is that in one of the studies few people were told that they might or might not receive an electric shock and few people were told that they would definitely receive an electric shock in a regular interval. So during this study, it has been observed that the people who received electric shock at a regular interval experienced lesser stress than the people who were do not know when and if they would receive an electric shock at all. So the suspense of not knowing what happens next made them more anxious than the people who took the shock but were sure when they would receive it. In a sense, being certain about a negative event made them mentally prepare for it in advance which made them feel less stress than the other group.
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