Participants were tested individually and told that they would be watching two teams of three players passing basketballs and that they should be paying attention to either the team in white or black. There were two different video qualities: opaque and transparent. Opaque conditions were filmed as a single action sequence.
The easy condition only requires participants to keep a silent mental count of the total number of passes made by the attended team. More observers noticed the the unexpected event in the easy condition (64%) than the hard (45%)
The hard condition required participants to separate silent mental counts of the number of bounce passes and aerial passes made by the attended team. More people noticed the unexpected event in the opaque condition (67%)