I think that this question could really only be answered in any meaningful way by conducting a scientific study – there may have been one or more done already but without having been presented with its findings, my answer could only be conjecture. I am inclined to agree, however, with Olmsted’s view that parks would probably be conducive to a positive attitude in a city’s populace. My own experience of cities is that they have such an effect. I feel very misanthropic (as if people are constantly and deliberately getting in MY way) on bustling streets, such as Oxford Street, or squares edged with buildings with high facades that shrink the sky – but when the paving turns to lawn, 30mph signs to trees, when the horizon descends nearer to eye level, then I can finally feel relaxed, less cynical, and it is as if the world were a little more as it should be.
I can’t speak for everyone. I’ve known some who relish the hustle and bustle of the hoi polloi – it makes them feel alive, that something is about to happen, that the world is opening up to them. I have no idea what percentage of the population would agree with this sentiment, but from my own very biased eyes, I would hazard a guess that more people on Oxford Street feel negatively towards their fellow pedestrians than do those strolling across, or even in sight of, Hyde Park. The no-man’s-land between the two that is Marble Arch must be an emotionally confusing place to be.