Inattentional blindness

Inattentional blindness, also known as perceptual blindness, is the phenomenon of not being able to perceive things that are in plain sight. It is caused by an absence of attention to the unseen object and is clear evidence of the importance of attention for perceiving. Without attention we are as if functionally blind. It is closely related to change blindness, which refers to our inability to perceive changes to features in scenes to which we are not attending. It is also related to the Attentional Blink, a phenomenon which occurs when we are searching for two particular target items in a rapidly presented list of items. We often fail to perceive the second target if it occurs between 150 and 400 msec after the first. This also is due to our failure to attend to the second target while attention is absorbed by the first one.

The term inattentional blindness was coined by Arien Mack and Irvin Rock in 1992. It was used as the title of Mack and Rock's book published by MIT Press in 1998. The book describes the discovery of Inattentional Blindness and the procedure used for revealing it.

The best-known study demonstrating inattentional blindness is the Invisible gorilla test, which was conducted by Daniel Simons of the University of Illinois at Urbana-Champaign and Christopher Chabris of Harvard University. Their study, a revised version of earlier studies conducted by Ulric Neisser, Neisser and Becklen, 1975, asked subjects to watch a short video in which two groups of people (wearing black and white t-shirts) pass a basketball around. The subjects are told to either count the number of passes made by one of the teams or to keep count of bounce passes vs. aerial passes. In different versions of the video a woman walks through the scene carrying an umbrella, or wearing a full gorilla suit.^[1] After watching the video the subjects are asked if they saw anything out of the ordinary take place. In most groups, 50% of the subjects did not report seeing the gorilla. The failure to perceive the gorilla or the woman carrying an umbrella is attributed to the failure to attend to it while engaged in the difficult task of counting the number of passes of the ball. These results indicate that the relationship between what is in one's visual field and perception is based much more significantly on attention than was previously thought.

Another experiment was carried out by Steve Most, Daniel Simons, Christopher Chabris, and Brian Scholl. They had objects moving randomly on a computer screen. Participants were instructed to attend to the black objects and ignore the white, or vice versa. After several trials, a red cross unexpectedly appeared and traveled across the display, remaining on the computer screen for five seconds. The results of the experiment showed that even though the cross was distinctive from the black and white objects both in color and shape, about a third of participants missed it. They had found that people may be attentionally tuned to certain perceptual dimensions, such as brightness or shape.

The basic Simons study was re-used on British television as a public safety advert designed to point out the potential dangers to cyclists caused by inattentional blindness in motorists. In the advert the gorilla is replaced by a moonwalking bear.

NASA conducted an experiment in a flight simulator in which commercial pilots were tested to see if they would notice distractions on a runway during simulated landings.^[2] Those who were trained pilots did not notice and landed directly on top of the distraction 1/4 of the time, while untrained pilots didn't know what to expect of a typical landing and thus saw the distraction.^[2]

Banner blindness

Banner blindness is a phenomenon in web usability where visitors on a website ignore banner-like information.

The term "banner blindness" was coined by Benway and Lane^[1] as a result of website usability tests where a majority of the test subjects either consciously or unconsciously ignored information that was presented in banners. Subjects were given tasks to search information on a website.

 The information that was overlooked included both external advertisement banners and internal navigational banners, e.g. quick links. The placement of the banners on a web page had little effect on whether or not the subjects noticed them. The result of the study contradicted the popular web design guideline that larger, colourful and animated elements on a website are more likely to be seen by users.

However, in an experiment by Bayles^[2] the results showed that users generally noticed web banners. This was proven by e.g. eye-tracking tests. The experiment concentrated on how users perceived a single web page and what they could recognise and recall of it afterwards. It has been argued that experiments like this without real-world tasks have poor methodology, and produce poor results.^[3]

Pagendarm and Schaumburg^[4] argued that a possible explanation for the banner blindness phenomenon lay in the way users interacted with websites. Users tend to either search for specific information or aimlessly browse from one page to the next. Users have constructed web related cognitive schemata for different tasks on the web. This hypothesis was also suggested by Norman.^[5] When searching for specific information on a website, users focus only on the parts of the page where they would assume the relevant information could be, i.e. small text and hyperlinks. Large colourful or animated banners and other graphics are in this case ignored. Usability tests that compared the perception of banners between groups of subjects searching for specific information and subjects aimlessly browsing seem to support this theory.