By a process of elimination, we came to the conclusion that it wasn't particularly the car in the woods, nor the chairs per se, but people sitting in the chairs was clearly just WRONG as far as some of the horses were concerned. Of course, not all the horses that passed us were worried, just a small handful, but for the ones that were we found that if we stood up and moved away from the chairs, the horses immediately calmed down quite alot. Perhaps they thought we were being eaten by the chairs!
I find this interesting in a number of ways. This is a type of scenario that the "Scary Corner" in Horse Agility is designed to address. Originally, the Scary Corner concept sprang from Roadworks, but our fun ride scenario fits the bill very well also. What they have in common is that it will be a more pleasant, safer ride if the horse's confidence can be built up, together with the horse's trust in its rider, so that the fear response can be replaced with a combination of confidence and curiosity. On a personal level, it did make me think, yes I do do all this Horse Agility with my ponies, and I have accustomed them to many different types of unusual stimuli, but would they accept a car with chairs and people in chairs in the woods? Knowing my ponies, I might assume that they would probably march up to the people and try to frisk them for treats, lol, but that is exactly the danger of taking things for granted and I'm now intrigued as to exactly how they would react! The next time I have a dry day with some spare time at the weekend, I'll be roping in the other half to get out the chairs and come and sit with me in the field, just to see how the ponies do react :-D