The benefits of indoor and stationary vs. outdoor aerobic exercise?
The Wikipedia page for Neurobiological effects of physical exercise (https://en.wikipedia.org/wiki/Neurobiological_effects_of_physical_exercise) is one of the best motivators to exercise I've ever found. Aerobic exercise in particular seems to have plenty of cognitive benefits. Here's one quote from the introduction of that Wiki page: "People who regularly perform aerobic exercise (e.g., running, jogging, brisk walking, swimming, and cycling) have greater scores on neuropsychological function and performance tests that measure certain cognitive functions, such as attentional control, inhibitory control, cognitive flexibility, working memory updating and capacity, declarative memory, spatial memory, and information processing speed.[1][5][7][9][10][14] The transient effects of exercise on cognition include improvements in most executive functions (e.g., attention, working memory, cognitive flexibility, inhibitory control, problem solving, and decision making) and information processing speed for a period of up to 2 hours after exercising." However, I haven't been able to find any information on whether there's a difference between indoor and outdoor versions of the same exercise. The obvious examples are running on a treadmill vs. running in a park or working out on a stationary exercise bike vs. cycling outside. Assume that we cloned someone and one version would perform an indoor version of some aerobic exercise and the other would do an equivalent amount of work outside. What, if any, differences should we expect to see? Would they be significant? Common sense tells us that outdoor cycling or running are more demanding across some dimensions. Cycling outdoors forces the cyclist to navigate a 3D space: he/she needs to avoid obstacles, slow down in anticipation of potential danger, make some adjustments if the surface is wet etc. It's also necessary to keep the bike balanced, adjust gears depending on the incline and so on. An outdoor cyclist is exposed to all kinds of weather conditions: high and low temperatures, wind, rain, glaring sun at noon or grey and cloudy dawn. Crucially skin and eyes will be exposed to natural light. Most people will ride a bike without headphones (and they certainly aren't watching YouTube clips on their iPads). In contrast we don't have to worry about any of these while working out on an exercise bike. I think we can reasonably hypothesize that the more challenging exercise will provide greater benefits. And that's the crux of the matter. Do we know anything about the magnitude of the difference? Did some researchers try to verify if there's really a difference in the benefits of indoor vs. outdoor exercise?
First and second order effects of dopamine deprivation
In your recent interview with Dr. Peterson, you described the dopamine biological cascade and some classic rat experiments, where the rat was dopamine deprived and would not move one body length for food. Is this a first order effect of low dopamine (causing an inability to think into the future and predict the reward), or is this a second order effect due to the biological cascade and a potential deficit in epinephrine formed from dopamine, causing a general lack of "neural energy", thus leading to an inability to function in general? If both, is there any sense of which is the bigger driver?