The fine, high arch was a dramatic look, designed to emphasize the plains of a woman's face, even if at times, it did give the wearer a rather startled, unnatural appearance.
In the 40s the trend veered toward medium thickness and a more understated look -red lips, heavy on the schtick, rather than brows, were the defining facial characteristic of that era.
|A young Joan Crawford in the 1930s|
|Joan Crawford's look reveals a change of brow fashion|
The change of styles can be seen clearly in actress Joan Crawford, who in the late 40s/50s chose a distinctly heavy, dark eyebrow arch - it certainly drew the eye, even threatening to overwhelm her facial features. In the 30s however, Joan had worn the classic Hollywood fine arches of the day.
In the 60s and 70s a more natural look was beginning to predominate. Interestingly, a 2007 study revealed that younger people prefer lower placed eyebrows with a subtle arch, while those over fifty favour a high arch.
How to Arch your Eyebrows