I once asked this question to a F-16 pilot who had been thru test pilot school, what he said is that on the F-16 they are needed for stability in the longitudinal axis at supersonic speeds. Maybe Roscoe or Gums have a more technical answer.
F-16A/B/C/D Mech AZ ANG/Top Gun
F/A-18A/B/C/D Mech Top Gun
F-14A Mech Top Gun
UH-60A/L Driver NV ARNG
It all works together....The wing and main fuselage body were smoothly blended into each other in three dimensions, making it impossible to define where the wing ends and the fuselage begins.
The blended wing-body, or lifting body effect is achieved by having a smooth fairing of the wing and fuselage rather than the conventional sharp intersection, providing improved lift at high angles of attack.
The wing was fitted with smoothly-blended leading edge strakes. These strakes create vortices at high angles of attack which maintain the energy of the boundary layer air flowing over the inner section of the wing, delaying the stalling of the wing root and maintaining the directional stability.
More than likely have "been there and done that at some point", it sure keeps you young if done correctly
From where they're placed it probably reduces dutch roll at high altitude. Lots of Learjets have them for that express purpose. Standard on the later models and STCed for earlier ones. Then again, the Viper is not a T-tailed aircraft and the FCLS would probably damp out any oscillations anyway.