I'll start by saying that I am not any more qualified in aerodynamics than ATPLs and a bit of experience have taught me
Anhedral in general destabilises the aircraft laterally. On a low wing it would for sure increase the spiral dive tendency and reduce the Dutch roll tendency. On a high wing anhedral is needed to destabilise highly stable wings.
Swept wing: increase Dutch roll tendency
Dihedral: increase Dutch roll tendency
Big rudder: increase spiral dive tendency
Anhedral: increase spiral dive tendency
Some times (often in my experience) aviation theoretical exams such as ATPLs or annual tech exams once on the line contain 'red herrings'. You're not going to find the perfect text book answer and certainly won't in real life. You have to for the most correct answer. It's like pilot maths: 2 x 2 = about 5!
Last edited by WhyByFlier; 9th March 2013 at 08:19.