Before I was an MIT graduate, I was a RUCCAS graduate. And I think I've mentioned enough MIT research that I should give a shout out to the Alma Mater.
Sean Duffy, an assistant professor of psychology at Rutgers–Camden... notes. “We began noticing a pattern: regardless of the receptacle’s label, recycling bins with little holes in the lids contained recyclables and almost nothing else, while those that lacked such holes were basically used as trash cans, even though they were recycling bins.”
The heroic hole in question measures about 6 inches in circumference, large enough for bottles made of glass or plastic. In the research team’s one-month study they observed 10 waste stations in a five-story academic building. Each station consisted of three container types: commingled glass, plastic, and aluminum; trash; and paper. Not only did the little hole increase recycling rates, but it lowered the amount of contaminants entering the recycling stream by 95%.