Rather than being confused by brown bears, Polar bears have a very consistent reaction to them. They are terrified by their brown cousins. Even a relatively small grizzly always runs off groups of polar bears from carcasses.
The knee jerk conclusion of many is that the polar bear is just more intelligent, thus will not risk injury. In fact, the polar bear’s less complicated life has actually left it slightly less intelligent than the brown bear from which it descended. Besides, it would be suicidal for them to abandon without reason their kills against a less formidable rival. The big white bears have had to go too far south, out of their normal range in search of food. They have already lost some weight due to hunger. They must have good reasons to give up an easy feast and run from brown bears.
Brown bears are not as weak compared to polar bears as some may think. They have the same size fangs, the same bite force, a more gaping bite, superior foreleg strength, and much longer, thicker claws. They are also far more robustly built.
Brown bears take down very big prey, like moose, elk, and caribou. Polar bears, on the other hand, almost exclusively kill two species of relatively small seals.
There is no predator that competes with the polar bear in its environment, while brown bears hijack the kills of cougars and packs of wolves. Brown bears are thus adapted for tough physical struggles.
Most importantly, however, while polar bears have great stamina when swimming in icy waters, they overheat very quickly on land, and even on frigid sheet ice. This is due to their superb insulation. In a struggle against a brown bear on warmer terrain, the polar bear would overheat even faster and collapse. As Muhammad Ali would have said, “You picked the wrong situation in which to get tired.” Instead of throwing themselves at the mercy of the smaller bear, polar bears exit Stage Left. There is no confusion here.