There was a lot about this years ago, claiming that goldens and blacks had issues. One our members, a trainer and behaviourist wrote his degree thesis on this . He disproved it because statistics were wrong. The blacks and golds had the highest number of naughty dogs. However, the majority of cockers were black or gold , so obviously outnumbered the rest.
My cocker was black and hard work ,but so were roans and tricolours on here at the same time. So-called cocker rage is rubbished because all breeds can have problems (just read of dog attacks). In the past, cockers were the largest breed group , so they just seemed to have a more public profile. Also people forget that they are working dogs, even the show type, and need brain work and exercise to be happy.
The blacks and golds that I have met over many years have been fabulous!!!
