Why is gauche conformer of 2,3 dimethyl butane more stable than its anti conformer?

Why is gauche conformer of **2,3-dimethylbutane** seen along 2,3 bond more stable than its anti conformer? It seems to be anomalous to me as in most other butane like compunds anti form is more stable than gauche form.Can someone explain me the reason why the compound shows [Gauche effect](https://en.wikipedia.org/wiki/Gauche_effect)?


Also does this anomaly hold in case of **2,3-diphenylbutane** and **2,3-dimethylpentane**?


