CHAIR metric

LVLM hallucination, AI Hallucination

Suggested in Rohrbach2018object.

It is simply the ratio between the number of hallucinated objects (sentences) and all objects mentioned (all sentences).

$$\text{CHAIR}_i = \frac{| \{ \text{hallucinated objects} \} |}{| \{ \text{all objects mentioned} \}| }$$ $\text{CHAIR}_s$ is similarly defined for the sentences containing hallucinated objects.