Final answer:
The slower detection of traffic signals described in the scenario is an example of inattentional blindness, which occurs when attention is focused on another task, leading to failure in noticing other visible objects in the environment.
Step-by-step explanation:
In driving-simulation experiments where students were found to be slower at detecting traffic signals while talking on cell phones, the phenomenon that best illustrates this is inattentional blindness. This refers to the failure to notice a fully visible, but unexpected object, because attention is engaged on another task or aspect of the environment. The studies conducted by researchers such as Most, Simons, Scholl, & Chabris (2000) and Daniel Simons and Christopher Chabris (1999) clearly demonstrate how attention is a significant factor in determining our perception, as shown when subjects focused on specific instructions failed to notice other visually prominent stimuli.
For instance, in the study by Simons and Chabris, nearly half the participants did not notice a person in a gorilla costume walking among the teams because they were so absorbed in counting the passes made by the team in white. This aligns with the scenario described in the question where the activity of talking on a cell phone distracts drivers so that they are slower in recognizing traffic signals, indicating the presence of inattentional blindness.