Bilojax, I think you're making too many assumptions based on movies.

"... they're more likely to spot a group than a solo."

Most people will be using a trail. Unless you're doing the E&E routine, and traveling across country in heavy cover, they're going to see you even if you're three feet tall. It's the motion that catches the eye in a still background.

"... they have to approach undetected..."

Again, no. The best attack under trail hike conditions is a direct attack from the front. Approach, smile and nod, grab or stab.

"...a solo hiker is more likely to be alarmed at the sounds of someone approaching than is a member of a group..."

An attacker doesn't have to approach -- all they have to do is get ahead on the trail, wait, and step out. It isn't like movie attackers that seem to come thrashing through heavy brush.

"... a member of a group is more likely to be distracted by talking or other interaction with his/her group, and the psycho can take advantage of the distraction to get close enough for his chain-saw atack."

Any single attacker who goes after a group would seem to me to be so totally unhinged (really rare) that all bets are off, but still, he's going to have to go after them one at a time, and he's never going to know if they are armed, know some serious self-defense, or if he's attacking a case of group-PMS.

"...one member of the group is likely to hear something strange and go off alone to investigate."

Only in the movies, sweetie. Divide and conquer. Most real people know there is more safety in numbers. Even the Mall Dolls know that.

"... the most numerous known psycho population near our hiking trails (mother bears foraging on one side of the trail with cubs on the other side) are more likely to be alarmed if a group of people come between her and her cubs than if a single person does."

I don't think number makes a difference. If she's worried about her cubs, I doubt that she will differentiate between one and several. The difference I do see is that if the victims scatter, one may get attacked and then MomBear will collect the kids and take off, and the others can then assist the downed hiker. But predicting bears is a real crapshoot, and many people who deal with them regularly will tell you that every bear is an individual and you will never know how they will react.

You'd best not base your survival skills and defenses on movies and TV, as the producers don't know squat and wouldn't know a good decision from a bad one.

Sue