Given a world with finite resources, some level of recycling is essential. But, even for resources that aren't especially limited—like paper—recycling can save energy and avoid the environmental disruption that comes from harvesting trees. Despite all the benefits of recycling, however, many of us do it only erratically.

A new study published in the Journal of Consumer Research attempts to explain why our recycling habit isn't as ingrained as we might like it to be. In it, two researchers (Remi Trudel and Jennifer Argo) show that our sense of an object's utility, as well as our penchant for categorizing something as trash, both feed in to whether people are likely to try to recycle it.

The research project started with the team rooting through the rubbish and recycling bins in one of their university's office buildings. During their after-hours trips through the trash, they noticed a rather distinctive pattern: sheets of paper that were close to the standard 8.5 x 11 inch size (this is the US, no A4 paper here) were more likely to be recycled, while smaller sheets tended to be thrown into the trash. This trend held even when the researchers adjusted for the total volume of paper in the different size categories.

The behavior of their co-workers led them to formulate a hypothesis: If a sheet of paper is close to the normal size we use every day, then people will mentally categorize it as still useful and will be more likely to recycle it. If, in contrast, it's a smaller size, then we'll view it as damaged and less useful. As a result, we'll tend to throw it in the trash.

To test this hypothesis, they came up with a series of experiments that were all based on a misdirection: they convinced their test subjects that they were there to evaluate a pair of scissors. During the tests, the subjects were asked to cut various sized sheets of paper into smaller portions (in half, into quarters, etc.), which produced sheets that had varying degrees of similarity to standard 8.5 x 11 sheets. Then, when the tests were over, the subjects were asked to dispose of the paper on their way out, where trash and recycling bins were waiting. (One research hazard: a fair number of the subjects took the paper with them, presumably to use for themselves. Those results were excluded from the analysis.)

The subjects consistently recycled paper if it ended up close to the standard paper size. To give one example: students given a standard sheet of paper or a double-size one, when asked to discard it, recycled the paper 80 percent of the time. If they cut the double-sized one in half, they ended up with a standard-sized paper, which they also recycled at an 80 percent rate. But, if they cut the standard sized one in half, resulting in two pieces of small paper, the recycling rate dropped in half.

Recycling rates for small pieces of paper went back up significantly if the authors asked the students to name five things the small sheets could be used for, suggesting that standard sized paper was simply viewed as useful, and therefore worth preserving (even if, in reality, recycling doesn't preserve the paper's shape in any way).

The researchers saw something similar with soda cans, as well. Regular cans were recycled more than 80 percent of the time, but if researchers gave participants a half-sized can, the recycling rate dropped to less than half—even though that's the normal state for that particular can. Put a dent in the can and, regardless of its size, the recycling rate dropped to somewhere in the area of 20 percent.

The authors conclude that there are multiple, overlapping processes of categorization going on. If we see an object as damaged—a dented can or small fragment of paper—we're more likely to categorize it as trash and treat it accordingly. In a similar manner, the more we see something as preserving its normal state, such as a full-sized soda can or standard-sized sheet of paper, we're more likely to consider it useful and worth of preserving through recycling.

The authors suggest that this behavior needs to be kept in mind if we want to increase recycling rates; things like packaging and food containers may typically be viewed as trash once they're emptied and are therefore less likely to be recycled. One alternative, however, is that human categorizations might ultimately adapt to the new reality of recycling and add a third category aside from useful and trash: recyclable.

Journal of Consumer Research, 2013. DOI: 10.1086/671475 (About DOIs).