We are biased to believe that what others are telling us is the truth. Researchers call this the “truth bias”. But why are we truth biased?
The traditional account sees the bias as an error in judgment, resulting from default or automatic ways of thinking that we just can’t control – in short, people are thought to be naïve and gullible, which is built into the very structure of how they think (e.g., Gilbert et al., 1990). But our account argues that the truth bias is not an error nor an uncontrollable way of thinking – rather, the bias is an indication of how people are making smart and informed guesses. This is embodied in the Adaptive Lie Detector or ALIED theory (Street, 2015).
Because the clues to deception are highly unreliable (DePaulo et al., 2003), we usually have to make a guess if someone is lying to us or not. How do we make that guess? We can rely on more general information about the context – for instance, most people tell the truth most of the time in our daily lives (Halevy et al., 2013). So it makes sense to guess people are telling the truth more often than guessing they are lying – and this, ALIED argues, is the source of the truth bias. If people expect others to lie, then, they should show a lie bias when they are unsure – and this is what we see (Street & Richardson, 2015a).
We have shown that general context information (most people will lie/tell the truth) has little effect when there are highly reliable clues. But as those clues become less and less reliable, people rely on more generalized context information to make an informed guess (Street, Bischof, Vadillo & Kingstone, 2015).
But what if people are not forced into making a lie-truth judgment at all? If they are usually guessing because the clues are usually unreliable, then presumably we can get rid of the truth bias by not forcing people into guessing. This is exactly what we have found. We find that people look like they can’t help but believe everything they hear (Gilbert et al., 1990), but that’s only because they are forced into guessing. When they can explicitly say they are unsure, this bias disappears (Street & Kingstone, 2016; Street & Richardson, 2015b).
In Street (2015), ALIED theory is outlined by building on research from decision making, person perception, child development, psycholinguistic, and neuropsychological evidence, amongst other subdisciplines. The theory also has clear impact for the practitioner: to increase lie detection, we need either to make the clues to deception more telling, or else we need to reduce the bias by preventing context-based guesses.
Street, C. N. H., Bischof, W. F., Vadillo, M. A., & Kingstone, A. (2015). Inferring others’ hidden thoughts: People make smart guesses in low diagnostic worlds. Journal of Behavioral Decision Making, 29(5), 539-549. doi: 10.1002/bdm.1904. [pdf] [blog]
Street, C. N. H., & Masip, J. (2015). The source of the truth bias: Heuristic processing? Scandinavian Journal of Psychology, 56, 254-263. [pdf]
Street, C. N. H., & Richardson, D. C. (2015a). Lies, damn lies and expectations: How base rates inform lie-truth judgments. Applied Cognitive Psychology, 29(1), 149-155. [pdf]
Street, C. N. H., & Richardson, D. C. (2015b). Descartes versus Spinoza: Truth, Uncertainty and Bias. Social Cognition, 33(3), 227-239. [pdf]