Contrastive Chain-of-Thought: pair each correct rationale with a labelled wrong one, teaching the model the reasoning boundary

Plain chain-of-thought hands the model a few correct worked examples and hopes it generalizes the right steps. It's genuinely strong — but I kept watching it walk into the same trap on multi-step arithmetic: adding when it should subtract, jumbling the step order, grabbing the wrong number. The problem is that a correct-only prompt draws just one side of the line. The model sees what good reasoning looks like and never what bad reasoning looks like. Contrastive CoT (Chia et al., 2023) closes…