Gamefreak has always liked physical boosts over special boosts
1st Gen it was even, they had SD for Attack, and Amnesia for Special
Then Belly Drum came along in 2nd Gen, and Amnesia became Sp Defence
3rd Gen we get Calm Mind... and Choice Band (increases attack)
4th Gen we get Nasty Plot, the equivilant of SD (or Amnesia from 1st Gen) and Choice Specs
Don't forget the Abilities like Huge Power and Pure Power, which doubles ATTACK
So there is no equivilant of Belly Drum for the special side of things, but the Pokemon games have always been physically disadvantaged anyway