It summarizes the results from an academic paper by Kate A.
Ratliff and Shigehiro Oishi that claims to show that men suffer a loss of self-esteem when they are told their girlfriends scored well on an intelligence test and when they were asked to recall an incident of their girlfriends' success.
In our simple terms, they would experience jealousy without the envy.
Focusing on the partners in committed relationships may gloss over the fact that each partner still faces potential competition from other people.
It is widely maintained that, at a very primal unconscious level, men seek out physically attractive women while women seek out successful men with status.
(This is a simplistic overgeneralization, I know, but bear with me.) It follows from this that women often worry that their male partners will leave them for more attractive women, and men often worry that their female partners will leave them for more successful men.
I was originally going to respond to this from the perspective of self-loathing men who never feel good enough for the woman they're dating or married to, and for whom this feeling of inadequacy is likely to increase when the woman enjoyed additional success.
(For my earlier blog posts on self-loathing, see the categorized list here.) On further reflection, however, I think this phenomenon makes sense for a lot of men in general—and a converse result would be expected for women as well.