A research team led by Rosanna Guadagno of the National Science Foundation showed 256 participants a video from a collection that spanned the emotional spectrum. Some saw a funny clip that had gone viral on YouTube. Others saw a hit that evoked anger. Still others saw a neutral video about basket-weaving. After the viewing, participants were asked whether or not they would share that video with someone else. Those who'd seen the funny video were significantly more likely to say they'd forward it than any of the other participants.

What type of experimental design was used in this study?