doi:10.1038/nn.4426 (paper) https://youtu.be/N1-1rbBarCk (audioslide)

Since the amygdala is associated with emotions, the increase in dishonesty may result from declining guilt about lying. The reduced amygdala sensitivity to dishonesty on a present decision relative to the previous one predicts the magnitude of escalation of self-serving dishonesty on the next decision. The findings uncover a biological mechanism that supports a 'slippery slope': what begins as small acts of dishonesty can escalate into larger transgressions.