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RUNNING HEAD: Monkey Business Illusion

Inattentional Blindness: The Monkey Business Illusion Pat Brown Australian Catholic University

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Inattentional blindness occurs when attention is focused on one aspect of a visual field and other aspects are not attended to and therefore not remembered. To investigate inattentional blindness in a dynamic scene, 120 psychology students watched a movie of moving people passing a ball to each other. In the middle of the movie, a gorilla walks through the people. The focused attention group were asked to count how many times the ball was passed, whilst the control group were simply asked to watch the video. Consistent with the hypothesis, significantly fewer participants in the focused attention group reported seeing the gorilla compared to participants in the control group. The findings of the study indicate that intentional blindness can occur in a dynamic scene. These findings shed light on the limitations of human attention and perception.

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Inattentional Blindness: The Monkey Business Illusion Attention is an important factor in visual processing (Moore & Egeth, 1998). Attention determines what we focus on and select for further processing (Atkinson & Shiffrin, 1971). Whilst people think that they see and remember all that occurs around them, this is actually not the case. The phenomenon responsible for this is called inattentional blindness (Mack & Rock, 1998), and it occurs when attention is focused on one aspect of the visual field and other aspects are not attended to and therefore not remembered. Many studies have been conducted to examine inattentional blindness. In these studies, participants engage in a task that requires them to focus on one aspect of a scene while ignoring others. During the task at some point an unexpected event occurs. Interestingly, the majority of observers do not report seeing the event even though it is clearly visible to observers not engaged in the concurrent task (Becklen & Cervone, 1983; Mack & Rock, 1998; Neisser, 1979; Neisser & Beckle,1975). Mack and Rock (1998) instructed participants to judge which of two arms of a briefly displayed cross was longer. On the fourth trial, an unexpected object appeared at the same time as the cross and, after the trial, participants were asked if they had seen anything other than the cross. They found that about 25% of participants are inattentionally blind when the cross was presented at fixation (that is, the centre of a person’s field of vision) and the unexpected event was presented parafoveally (outside the point of fixation). About 75% of subjects were inattentionally blind when the cross was presented parafoveally and the unexpected object was presented at fixation,

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suggesting an effortful shift of attention away from the fixation point to the cross and possible inhibition of processing at the ignored fixation point. These findings suggest that if attention is directed at the fixation point, then objects in this area and the area immediately around it are more likely to be detected. Despite several studies examining inattentional blindness, research has typically examined whether participants report seeing static unexpected events or objects when their attention is focused on something else (Mack & Rock, 1998; Neisser & Becklen, 1975). Dynamic unexpected objects or events may be more noticeable and capture attention more readily than static unexpected events (Simons & Chabris, 1999). The aim of the current study was to examine whether people report seeing an unexpected dynamic event when their attention is focused on another task. Participants were asked to count how many times a ball is passed between moving players wearing white shirts. During the task, a gorilla walked through the players. Participant reports of seeing the gorilla comprised the dependent variable. Compared to participants not receiving any instructions whilst they watched people tossing a ball together, it was expected that participants instructed to count how many times a ball is passed between players wearing white t-shirts will be less likely to report seeing a gorilla who walked through the players. Method Participants One hundred and twenty first year psychology students from three campuses (Brisbane, Melbourne, and Sydney) of an Australian university participated in the study. Participants were recruited through advertisements

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on an internal university website. Course credit in a first year psychology unit was provided to students who completed the study. The participants mean age was 21.5 (S.D.=3.7) and 100 (83%) participants were female. Materials The materials consisted of a video recording of the ball tossing game and a response form. The video recording of the ball tossing game showed 6 women ball players, three wearing white shirts and three wearing black shirts. The players tossed a ball between themselves whilst moving around in an open area in front of a red curtain, but the players in white shirts only tossed the ball to players wearing the same coloured shirt (and the same for the players in black). After tossing the ball for 27 seconds, a gorilla walks through the players from the right to the left of the screen and beats his chest when he is in the middle of the players. The gorilla is on screen for approximately 6 seconds. The players passed the ball for 40 seconds before walking away. The response form asked the participants to record how many times the players in white passed the ball and whether they had seen anything unusual whilst watching the video and to describe what it was. Procedure All participants were tested individually. Participants were told that the ostensible purpose of the study was to look at the effect of individual differences in sport. Participants were randomly assigned to the attention or control conditions. Participants were then seated in front of a video monitor and asked to wear sound reducing headphones to reduce the effect of random noise on attention. They were told that they would be watching a short video of a ball tossing game and to pay attention. Participants in the

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attention condition were additionally instructed to keep a silent count of the number of ball tosses between the players in white shirts. Participants then watched the video and recorded their answers on the response form. At the end of the study, participants were debriefed about the real purpose of the study. Results The percentage of participants who reported seeing the gorilla in each condition can be seen in Figure 1. All participants in the control group reported seeing the gorilla, whilst only half of the participants in the focused attention condition reported seeing the gorilla.

100 90 80 70 60 50 40 30 20 10 0 Focused attention

Control

Figure 1. Percentage of participants who reported seeing the unexpected event in the focused attention and control conditions. When a chi-square analysis was conducted, the results showed a statistically significant difference between the participants instructed to count

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ball tosses (focused attention) and those who did not (control) on reports of 2 seeing a gorilla, χ (1, 120)=8.65, p...