I’ve just read Public perceptions of energy consumption and savings (Attari et al. 2010), and apart from from being a pretty good paper, it’s quite well aligned with the results of my dip study, and Hanson’s Homo Hypocritus theory.

Gardner and Stern (6) also speculated that people harbor misconceptions about the effectiveness of their actions. For example, “turning out lights when leaving the room” is often suggested as a way to save energy, but it actually saves very little … Larrick and Soll (11) reported that people in the United States mistakenly believe that gasoline consumption decreases linearly rather than nonlinearly as an automobile’s gas mileage (in miles per gallon) increases. Describing vehicles’ fuel efficiency in terms of “gallons per 100 miles” corrected this misperception and led to more fuel efficient choices. … For example, participants estimated that line-drying clothes saves more energy than changing the washer’s settings (the reverse is true)

The part that I found most interesting was:

The coefficient for numeracy (23) was positive in all five tests and significant in four, indicating that participants with a better understanding of numerical concepts had more accurate perceptions of energy consumption and savings. The coefficient for the New Ecological Paradigm (NEP) score (24) was positive and significant in four of the five tests, indicating that participants with more proenvironmental attitudes had more accurate perceptions. These two effects were substantial.

but

Surprisingly, participants’ self-reported environmental behaviors scale always had a negative coefficient and was significant in three of the five tests, indicating that participants who reported engaging in a greater number of proenvironmental energy-related behaviors had less accurate perceptions.

So it would seem that knowing how to quantitatively address the world is a good thing, and that if you make a noise about how much you care about the world then you are probably doing more work signalling that to others that you care than actually doing anything useful!

Interestingly, the curves that the authors developed from their responses match the curves that turn up in everything that I’ve seen on confidence. People in this study over estimate the effects of the small things that they do (unplugging phone chargers) and under estimate the effects of things that actually have a big effect (transporting goods by train rather than truck).