Attention and Visual Perception • 97one picture, followed by a blank fi eld, followed by the
same picture but with an item missing, followed by the
blank fi eld, and so on. The pictures were alternated in
this way until observers were able to determine what was
different about the two pictures. Rensink found that the
pictures had to be alternated back and forth a number of
times before the difference was detected.
This diffi culty in detecting changes in scenes is called
change blindness (Rensink, 2002). The importance of
attention (or lack of it) in determining change blindness is
demonstrated by the fact that when Rensink added a cue
indicating which part of a scene had been changed, par-
ticipants detected the changes much more quickly (also see
Henderson & Hollingworth, 2003; Rensink, 2002).
Change blindness has also been demonstrated by
having observers view fi lms. ● Figure 4.21 shows succes-
sive frames from a video of a brief conversation between
two women. The noteworthy aspect of this video is that
changes take place in each new shot. In shot B, the wom-
an’s scarf has disappeared; in shot C, the other woman’s
hand is on her chin, although immediately after, in shot D,
both arms are on the table. Also, the paper plates change color from red in the initial
views to white in shot D.
Although participants who viewed this video were told to pay close attention, only
1 of 10 participants claimed to notice any changes. Even when the participants were
shown the video again and were warned that there would be changes in “objects, body
position, or clothing,” they noticed fewer than a quarter of the changes that occurred
(Levin & Simons, 1997).
This blindness to change in fi lms is not just a labora-
tory phenomenon. It occurs regularly in popular fi lms, in
which some aspect of the scene, which should remain the
same, changes from one shot to the next, just as objects
changed in the fi lm shots in Figure 4.21. These changes
in fi lms, which are called continuity errors, are spotted by
viewers who are looking for them, usually by viewing the
fi lm multiple times, but are usually missed by viewers in
theaters who are not looking for these errors. For example,
in the fi lm Oceans 11 (2001), Rusty, the character played
by Brad Pitt, is talking to Linus, the character played by
Matt Damon. In one shot, Rusty is holding a cocktail glass
full of shrimp in his hand, but in the next shot, which
moves in closer and is from a slightly different angle, the
glass has turned into a plate of fruit, and then in the next
shot the plate changes back to the cocktail glass! If you are
interested in exploring continuity errors further, you can
fi nd websites devoted to them by searching for “continuity
errors in movies.”
All of the experiments we have described—both the
ones in which a distracting task kept people from notic-
ing a test stimulus and the ones in which small, but easily
visible, changes in pictures are not perceived—demonstrate
that attention is necessary for perception. This has implica-
tions for perception that occurs in our everyday experience,
because there are usually so many stimuli present in the envi-
ronment that we are able to pay attention to only a small
fraction of these stimuli at any point in time. This means
that we are constantly missing stimuli in the environment.● FIGURE 4.21 Frames from the video shown in the Levin and
Simons’ (1997) experiment. Note that the woman on the right is
wearing a scarf around her neck in shots A, C, and D, but not in
shot B. Also, the color of the plates changes from red in the fi rst
three frames to white in frame D, and the hand position of the
woman on the left changes between shots C and D. (Source: From
D. Levin & D. Simons, “Failure to Detect Changes in Attended Objects in Motion
Pictures,” Psychonomic Bulletin and Review, 209, 1997.)
(a) (b)
(c) (d)
● FIGURE 4.20 What is diff erent in this picture?
Bruce GoldsteinCopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.