These clips demonstrate how sometimes it can be difficult to spot unexpected changes in a visual scene - so called “change blindness”. Watch the clips, and see if you can spot the changes in them. Have a go and then read the explanation. The images flicker rapidly so be careful if you are sensitive to rapid light changes.
The Intriguing Story of Change Blindness.
By Ken Scott-Brown, University of Abertay Dundee
The clips on this page demonstrate how sometimes it can be difficult to spot unexpected changes in a visual scene - so called “change blindness” (Ron Rensink and his co-worders made this famous in 1997). Most of the time we trust our eye to detect changes easily, and we normally manage this without difficulty.
These Demos were made by Calum Wallace, Chris Horgan and Matt Stainer while working in the Perception Laboratory at the University of Abertay Dundee.
Did you find some easier than others? Were some tricky? Each picture was from Dundee, and it flashed on every quarter of a second. However every second flash of the scene incorporated a change (such as removal of an object from the scene). Provided the scene flickers are interspersed with short grey blank intervals, it can be infuriatingly difficult to spot that something as obvious as a car or a pathway has been “photoshopped” from the picture.
These demonstrations may not immediately appear to be relevant to the tasks of people in every life, but think about observers in CCTV control rooms. Ron Rensink found that the crucial determinant of whether or not these “changes” are detected is the amount of visual disruption used. Other researchers have shown that blinks and splashes also cause change blindness. As well as surveillance, people are realizing that drivers in traffic might be at risk of change blindness.
One special form of “change blindness” is “inattentional blindness”, and perhaps the most famous demonstration of inattentional blindness is the widely publicised “Gorillas in our Midst” experiment by Dan Simons and Chris Chabris (1999) - you can see a demonstration of this in Sensation.
Rather worryingly, even people that know about change blindness and have experienced it themselves still overestimate their ability to detect unexpected
changes. Daniel Levin and his co-workers (2000) call this overestimation “change blindness” blindness (get it?).
Links:
1. The original examples of the change blindness demos are available from Ron Rensink’s web site:
http://www.psych.ubc.ca/~rensink/flicker/download/
2. Some excellent and amusing examples of person swop experiments are available to view on line at Dan Simons’ web site: http://viscog.beckman.uiuc.edu/djs_lab/demos.html
