Ambidirectional dominance

Ambidirectional dominance occurs in a situation where multiple genes influence a phenotype and dominance is in different directions depending on the gene. For example, gene A causes increased height, while gene B causes decreased height. 
The opposite situation, where all genes show dominance in the same direction, is called directional dominance. In the same example, both genes A and B cause increased height. According to Broadhurst, ambidirectional dominance is the result of stabilising selection in the evolutionary past. Ambidirectional dominance has been found for exploratory behaviours in mice and Paradise fish.