We all know we should recycle, but even committed recyclers can be erratic, cleaning and sorting bottles one day, and tossing glass in the trash the next. Why? It turns out that an array of biases sway our decisions about what to place in the green bin and what to throw away.

Two such biases emerged in research my colleagues and I recently conducted on disposal habits. First, we found that people are more likely to recycle items that haven’t been distorted—like undented soda cans and paper that hasn’t been torn into pieces (we call this the “distortion bias”). Second, they are more likely to recycle items linked to an element of their identity—a Starbucks cup with their name on it, for example (the “identity bias”). A third factor affects not what we recycle, but how much we do: People who know they are going to recycle after completing a task that generates waste use far more resources than they otherwise would have.

My colleague Jennifer Argo and I first noticed the distortion bias when we examined the contents of the recycling and trash bins in 22 academic offices. In general, intact pieces of paper were recycled; paper fragments were trashed. We confirmed the finding through several subsequent experiments, including two in which participants believed they were evaluating a new pair of scissors. All were given instruction sheets for the evaluation; some were asked to cut up the sheets as part of the evaluation while others weren’t. All were then asked to dispose of the waste on their way out. Participants with uncut pieces of paper generally put them into the recycling bin; those left with paper fragments put them in the trash. We attained similar results with aluminum cans—intact cans were recycled, dented or crushed cans were trashed.

What explains this bias? When an item is sufficiently distorted or changed in size or form, people perceive it as useless—as something without a future. So they throw it in the trash. This partially explains why so much recyclable material winds up in landfill instead. Though we have all been trained to recycle many common items, the EPA estimates only about 65% of paper and 55 % of aluminum gets recycled. By making people aware of this bias, we could potentially change disposal behavior. And sustainability minded companies could improve recycle rates through innovations in packaging that, for example, increase ease in opening and decrease distortion, which could improve the likelihood that packaging will be recycled and even reused.

Our exploration of the identity bias was motivated by a trip to a coffee shop where the barista misspelled my name on the coffee cup. Writing patrons’ names on cups has become standard at many coffee shops, linking the product with some piece of their identity. To test this, Jennifer Argo, Matthew Meng, and I asked a group of volunteers to sample and evaluate juice. Participants were asked their names, which we then spelled either correctly (Sarah, Paul, Ashley) or intentionally misspelled (Saruh, Pawl, Ashlee) on their cups. Those whose names were spelled correctly were significantly more likely to recycle their cup than those whose names were misspelled. We conducted several other studies with different products and different ways of linking the product to consumers’ identities—like using American flags or university logos that link people to important group identities. We consistently found that people are more likely to recycle than discard identity-linked products – and that trashing these products can lower self-esteem. As might be expected, it feels bad to throw a piece of yourself in the trash, so people avoid it. By creating an identity link or making an existing link stronger, we might make consumers less likely to trash recyclable items. Many firms already link products to our identities but may not be aware of the disposal consequences. For instance, Coca-Cola’s “Share a Coke” campaign, where consumers find their names on bottles of Coke, is likely to increase recycle rates for those who drink from a bottle with their name on it.

Sometimes the option to recycle may bias how much of an item we use. For example, my colleague Monic Sun and I examined how much people consume when they have the option to recycle versus throw away. Research subjects were instructed to use as much or as little of a product as they wanted. In one study they wrapped gifts; in another they used scrap paper to solve math problems, and in another they selected a gift. In each experiment, half of the participants could recycle what they used; the other half could only discard it. We consistently found that people used far more resources (wrapping paper, scrap paper, plastic cups, plastic packaging) when they knew they were going to recycle.

How can we account for this? Our findings suggest that the positive emotions associated with recycling can overpower the negative emotions, like guilt, associated with wasting. As a result, consumers feel comfortable using a larger amount of a resource when recycling is an option. Conserving resources in one domain may lead you to waste resources in another—in effect, giving yourself a pass because of your prior good behavior – a phenomenon known in social science as “moral licensing.”

To recycle or to trash? The success of recycling depends on the answer billions of people give to that question daily. As we’ve learned from behavioral economists in recent years, many of our decisions are, in the words of Dan Ariely, “predictably irrational.” So it is with this decision. But by bringing our disposal biases to light, we can alter individual behavior, spur the creation of packaging that encourages recycling, and increase the effectiveness of environmental policies and campaigns.