Wiktionary
a. 1 (context literally English) On the head. 2 (context figuratively English) Inside the head. 3 (context informal English) In the brain or in the mind.
Wikipedia
Between the Ears is a programme on BBC Radio 3 that airs brief documentary features in experimental formats. A season of Between the Ears programmes is produced roughly twice a year, and when the programmes are in season they are broadcast late on Saturday nights, UK time.
Usage examples of "between the ears".
Tito was a pretty little creature, with woolly body, a puppy-like expression, and a head that was singularly broad between the ears.
Two ridiculous ears stood high, and a little tuft of golden hair showed on the crest of the head between the ears.
Cadderly patted the squirrel between the ears with a single finger¯.
Wycliffe is considered quite a catch, though it's said he's not terribly well-endowed between the ears.
Tatzel, absorbed in her own thoughts, rode with her gaze directed between the ears of her horse, at a point in the middle distance, and ignored Aillas' tension.
Tatzel, absorbed in her own thoughts, rode with her gaze directed between the ears of her horse, at a point in the middle distance, and ignored Aillas’.
But unless it has that stuff between the ears that a man has, it is not a man, it's not even a corpse.
But even if Bores-me did not have buttocks like sofa cushions, he's much too fat between the ears.