People achieve an average of 54% correct lie-truth judgments

From Accuracy of Deception Judgments by Charles F. Bond Jr. and Bella M. DePaulo. So in the most basic situation of trying to discern the truth about our environment (the world outside of our individual selves), in a social circumstance where we are trying to discern truth from falsehood, we only get it right about 50% of the time. Yikes! That is a distressingly high noise to signal ratio.

We analyze the accuracy of deception judgments, synthesizing research results from 206 documents and 24,483 judges. In relevant studies, people attempt to discriminate lies from truths in real time with no special aids or training. In these circumstances, people achieve an average of 54% correct lie-truth judgments, correctly classifying 47% of lies as deceptive and 61% of truths as nondeceptive.