People often times fail to detect changes in scenes they observe. We examined theme, whether an object was related to a scene or not, as well as object change, whether the object was added or deleted to the previous scene, would effect the reaction time in identifying a change. Participants were randomly assigned to one of two object change conditions (add or delete) and then were asked to judge whether or not there was a change involving scenes with related objects changing, as well as scenes with unrelated objects changing. The results showed a main effect of theme but no main effect of object change as well as no interaction between the two independent variables.

1. Change Blindness with 1
Running head: CHANGE BLINDNESS WITH THEME AND OBJECT CHANGE
Change Blindness with Scene Themes and Adding and Deleting Objects
Gina M. Martino
Northern Illinois University

2. Change Blindness with 2
Abstract
People often times fail to detect changes in scenes they observe. We examined theme, whether
an object was related to a scene or not, as well as object change, whether the object was added or
deleted to the previous scene, would effect the reaction time in identifying a change. Participants
were randomly assigned to one of two object change conditions (add or delete) and then were
asked to judge whether or not there was a change involving scenes with related objects changing,
as well as scenes with unrelated objects changing. The results showed a main effect of theme but
no main effect of object change as well as no interaction between the two independent variables.

3. Change Blindness with 3
Change Blindness with Scene Themes and Adding and Deleting Objects
All throughout history, humans have placed a lot of faith in the accuracy of
understanding and remembering the scenes, events, and people they see. A perfect example of
this is eyewitness testimonies in crime investigations. These rely on individuals to recall
something they saw over an extended time period. However, there is some evidence to suggest
that people cannot even accurately identify something that has just happened, or is happening
right before them. Everyday people are exposed to a myriad of visual information, so it only
makes sense that there would be some discrepancy in a person’s recollection of events.
Certain studies have examined the meaningfulness of an object determining how easily
detectable a change in it would be. In one experiment, the ease in detecting change in faces was
compared with the ease in detecting change in other common objects. Although participants
reported detecting change in faces to be one of the more difficult tasks, there was a good deal
lower percentage of error in detecting change in faces than all the other objects used, suggesting
that a person may perceive a task as more difficult than it is (Ro, Russell, & Lavie, 2001).
Other studies suggest that if a person’s attention is focused on something, they will not
notice an unexpected object or occurrence. Simons and Chabris (1999) explored this theory in an
experiment in which participants were asked to count how many times a basketball passed
between members of a team. While the participants’ attention was focused on this activity, a
person in a gorilla suit or a woman with an umbrella would walk through the middle of the
scene. The gorilla or the woman with the umbrella was used as a way to test whether an object
more or less related to the scene would be more noticeable. Whether or not the person noticed
this out of place individual passing through was then questioned. It was found that the

4. Change Blindness with 4
woman with the umbrella was noticed more often, suggesting that something that belongs less in
the scene was least likely to be noticed.
Hollingworth, Williams, and Henderson (2001) also explored whether an object fits with
the scene or not determines how noticeable it is, however they went further with this to explore
whether the details of the scene decay immediately or if they are stored in the brain for later
access. Their results showed evidence that details are indeed stored for longer periods of time,
and more so when the object does not fit with the scene.
Most previous experimentation on change blindness was done using images or videos on
a computer or projected by some other device. Simons and Levin (1998) saw this as a possible
influence on the ability of people to detect change and decided to create an experiment using real
life observations of participants. In this experiment, the change would happen right in front of
unknowing participants eyes as a door passed between the participant and the experimenter while
the experimenter changed places with one of the men carrying the door.
Overall, there are two ways in which a person can recognize change: detection and
identification. Often times, a person is able to detect that a change has occurred, and they may
even be able to identify the general area in which it occurred, however they cannot always tell
what specifically changed (Rensink, 2002; Agostinelli, Sherman, Fazio, & Hearst, 1986).
Utilizing changes within ambiguous and meaningful images, Agostinelli et al (1986) set
out to support the hypothesis that when an object was added to a previous scene, it would be
easier for participants to identify the object than if the object were deleted from the scene. In
their first experiment where participants were unaware that they would have to identify a change,
this hypothesis was supported. However, during the second experiment, participants were told at

5. Change Blindness with 5
the beginning they would need to later identify a possible change, deletions were recognized
with more accuracy therefore not supporting the hypothesis.
The present study believes in two hypotheses. First based on Hollingworth, that objects
that are unrelated to the scene they are in are more likely to be noticed than objects that belong.
For instance, an office chair outside will be more noticeable than whether or not someone is
wearing shoes indoors. The second hypothesis based on Agostinelli, is that the deletion of an
object from a scene will be more easily noticed than the addition of the same object to the same
scene.
Methods
Participants
Thirty-six introductory psychology students from a Midwestern University participated in
the experiment for class credit. Participants were randomly assigned to one of two object change
conditions, 16 to the add condition and 20 to the delete condition.
Materials
The experiment will be conducted using ePrime stimulus presentation on computers in
individual rooms. Pairs of pictures were constructed to be shown in varying order. Each pair
contained on change which was either related or unrelated. For example, one scene was of a
snowboarder outside and the object that was changed was a shadow in the background, this item
fit naturally into the scene. Another scene was of two people talking outside and the object that
changed was a bright green indoor chair. In one condition, participants saw the change as an
addition to the previous image , in the other condition they saw the change as a deletion from the
previous image.

6. Change Blindness with 6
Procedure
Participants were greeted as they arrived and asked to sit in one of eight rooms. They
were asked by an experimenter to read and sign an informed consent form before continuing
with the experiment. This experiment was a 2x2 design. Participants were randomly assigned as
they arrived to one of two between subject object change conditions, add or delete, which served
as the first independent variable. For example, in the add condition, a scene was shown of a hotel
room with a blank wall, and in the second scene the wall would have a picture on it. The second
independent variable, theme, occurred within subjects. The two levels were related and
unrelated, and were based on whether the change involved something that would naturally occur
in the scene or not. The experimenter read the instructions to the participant that was displayed
on the computer screen. Participants were then presented with one scene until they pressed a key
to continue. After pressing the key, there was a 2000ms blank screen and then the same scene
again only with some alteration. The difference between the two conditions was that the second
scene either had something added to it, or subtracted from it. Participants then had to decide if
something in the second scene changed or not by pressing the “d” key if they saw no change, or
the “k” key if they saw a change. If they decided that it has changed, they were asked to type
what it was that changed in the following screen. All scenes contained a change. When finished
with all the scenes, the participants were told to notify the experimenter that they were finished
and were then given a debriefing form explaining the purpose of the experiment.
Results
This experiment set out to find whether there is an effect on change blindness based on
whether an object is related or unrelated, as well as whether or not an object is presented as an

7. Change Blindness with 7
addition or deletion. A two-factor ANOVA was conducted based on reaction time for the two
independent variables (theme and object change). The first hypotheses regarding the effect of
theme (related vs. unrelated) was supported as the data showed a main effect for theme, F(1, 34)
= 12.30, MSE = 852345.719, p < .01. See Table 1 for means and standard deviation. This effect
supports the prediction that individuals are quicker to respond to unrelated objects
(M=3665.7500, SD=1752.92145) than to related objects (M=4406.0278, SD=1824.67554).
However, the second hypotheses regarding the effect of object change (add vs. delete) was not
supported. The data showed no main effect for object change, F(1, 34) = 1.23, MSE =
5505618.859, p >.05. This suggests that individuals are no quicker to notice a change whether it
is added to the scene or deleted from the scene. The data also showed no significant interaction
between theme and condition, F(1, 34) = 1.299, MSE = 852345.719, p > .05. This serves to
suggest further, that whether an object is added or deleted does not effect a person’s reaction
time, regardless of whether the object involved was related or unrelated.
Discussion
The goal of this study was to examine change blindness and the effects of certain visual
variables on an individual’s reaction time. The results showed that while whether an object was
related to a scene or not did have an effect on reaction time, whether that object was added to or
deleted from the previous seen had no apparent effect. This supports the first hypotheses, but not
the second. Also, when examining the relationship to previous studies on change blindness, we
see that the data supports the conclusion of Hollingworth et al. (2001), while challenging that of
Agostenelli et al. (1986).
One particular problem I saw with the procedure of the experiment, was the keys used to

8. Change Blindness with 8
identify whether a participant noticed a change or not. The letters K and D were ambiguous and
could have caused a greater delay in reaction time than if more related letters were used. Even
more detrimental, the delay may have been greater for the first few slides, but the participants
may have sped up as they went along. To control for this difficulty, several things could be done
in the future. First, the letters chosen could be more related, such as Y an N (for yes there is a
change and no there is no change) or C and N (change and no change). Finally, a key stating
which key to press could be added to the images or placed on the computer monitor, although
this again could cause a difference in speed over the course of the experiment.

9. Change Blindness with 9
References
Agostinelli, G., Sherman, S. J., Fazio, R. H., & Hearst, E. S. (1986). Detecting and
identifying change: Additions versus deletions. Journal of Experimental
Psychology, 12(4), 445-454.
Hollingworth, A., Williams, C. C., & Henderson, J. M. (2001). To see and remember:
Visually specific information is retained in memory from previously attended
objects in natural scenes. Psychonomic Bulletin & Review, 8(4), 761-768.
Rensink, R. A. (2002). Change detection. Annual Review of Psychology., 53, 245-277.
Ro, T., Russell, C., & Lavie, N. (2001). Changing faces: A detection advantage in the
flicker paradigm. American Psychological Science, 12(1), 94-99.
Simons, D. J., & Chabris, C. F. (1999). Gorillas in our midst: Sustained inattentional
blindness for dynamic events. Perception, 28, 1059-1074.
Simons, D. J., & Levin, D. T. (1998). Failure to detect changes to people during a real-
world interaction. Psychonomic Bulletin & Review, 5(4), 644-649.

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Table 1
Time Taken to Identify Change in Theme Condition
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Mean Standard deviation
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Unrelated reaction time (ms) 3665.7500 1752.92145
Related reaction time (ms) 4406.0278 1824.67554
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