ambiversion

noun

1. (uncountable)A personality trait having balanced characteristics of both extroversion and introversion.

   “The definition of ambiversion grows then directly out of the two preceding [extroversion and introversion] and is to be stated as a condition of development in which attention is controlled by either objective or subjective conditions of attention and in which the content of the subjective conditions is so varied as to make possible more or less prolonged periods of either extroversion or introversion.”