Strayer and Johnston were investigating the link between cell phone use and the ability to react to environmental stimuli. While the participants tracked a moving target using a joystick, they were required to press a button each time a red light flashed at random points on a computer screen. While completing the task, one group used a hand-held cell phone to carry on a conversation, one group

used a hands-free cell phone, and one group was not engaged in any conversation. The researchers measured the time that elapsed between the appearance of the red light and the button press. The results from this study suggested that compared to the group that was not engaged in any conversation, people engaged in a cell phone conversation:

a. detected the red light each time it was present, but were slower to react to the red light
b. failed to detect the red light more often, but had equally quick reaction times when the red light was detected
c. only showed slower reactions times if they were using a hand-held cell phone
d. failed to detect the red light more often, and were slower to react to the red light when it was detected

D