I haven’t seen this brought up much in drawing guides, and it’s a mistake I used to make and that I see a lot, mostly in young artists but occasionally in professionals’ stuff and it’s really simple-
A lot of artists don’t make the back of their character’s heads big enough, the part behind the ear is collapsed a lot of times. The ear is more or less above the middle of the neck when seen from the profile. The width of the head in front of the ear (if you slice off the facial feature area..), and the width of the head from the ear and back are almost the same.
I think a lot of people draw the back of the head depending on where the back of the neck is, and that’s unreliable. The shape of the back of the neck connecting with the back of the head changes depending on how big your trapezoid is. If you want someone to instantly look buff just make the back of their neck go up to the middle of the back of the head lol.
used this stock for the girl profile