  The dynamics of two heavy quarks inside the same hadron is probed against the
double charm baryon results of SELEX. This can be seen as a part of the
mechanism to bind tetraquarks with two heavy quarks and two light antiquarks.
In the framework of potential models, it is possible to test the role of
different effects: relativistic corrections, confinement, hyperfine forces,
etc. It is conjectured that an additional interaction rescaled from the
nucleon--nucleon system and acting between light quarks only, can help in
bringing extra, possibly required, binding in tetraquarks.
