Change blindness is the inability to detect changes within a scene. Inattentional blindness occurs when people have a hard time perceiving stimuli if attention resources are focused elsewhere. Both of these phenomena were noticed by Harvard Psychologist William James who based his personal observations on our effort to “focus on some things in exclusion to others (1890, as cited by Goldstein, 2012).” He went on to suggest that the perceptual system has a limited capacity for processing information. James believed that in order to not overload the visual system, we purposely ignore some things in our environment so that full attention can be paid to others.
One study that demonstrated inattentional blindness was carried out by Simons and Chabris (1999). According to the researchers, our attention to the central interest in a scene inhibits the ability to perceive changes that are of marginal interest. In the study a video recording depicted a team wearing black and a team wearing white. Each team had a basketball that was passed among the group. Observers were asked to keep track of either the total amount of passes that one team made or keep track of only the amount of aerial or bounce passes made by one team. Each task was given a level of difficulty; easy and hard respectively. During the observation a woman with an umbrella or a woman in a gorilla suit would pass through the scene, which served as an unexpected event. Almost half of the observers failed to notice the highly salient and unexpected event while engaged with the monitoring task. The results show that the primary task given to the observers affected whether an unexpected event was more or less attended to; harder primary tasks made it more difficult for the observer to notice the unexpected event. Something unexpected could pass right before the observers' eyes and still not be detected.
The above study shows how an irrelevant unexpected event can induce inattentional blindness in some people. But what if the unexpected event is more relevant than a woman in a gorilla suit at a basketball practice? A recent study by Kennedy and Bliss (2013) observed inattentional blindness by utilizing relevant task stimuli. In the experiment they created a driving simulator where drivers were given six auditory directions. Each direction was given to the driver, as they maneuvered through an urban area, about every 1000 feet. The goal of the driving task was to make it to the end by following the auditory directions and driving laws. The simulator had obstacles that were indicative of urban settings, such as people and buildings, although they did not interfere with the driver. The last auditory direction prompted the driver to make a left-hand turn at an intersection. At the left-most corner of the intersection, a “No-Left Turn” sign was positioned. The results showed that 80% of the drivers failed to detect the sign and made the illegal turn because the auditory directions...