EVANSTON — A Psychology Department study shocked Northwestern student groups this week with the controversial claim that taping advertisements to the ground is not an effective way to market a club, cause, or event. For decades now, Northwestern students have been paving sidewalks with flimsy, exposed, and flamboyant pieces of paper. For the first time in Northwestern history, students are questioning the status quo and boldly considering whether they should continue to litter the streets with their short-lived posters. Some