Inattentional Blindness
Words
1759501
Tutor group: 31
University of Birmingham
Introduction
Attention is a mental process by which we choose to focus on some things to the exclusion of other things. Since attention is a limited resource, we have to be selective about what we decide to focus on. When we look at an object we usually pay ‘attention’ to it. But, we can look at something without attending to it. Therefore we must direct our attention to the things we want to perceive.
Inattentional blindness is a phenomenon in which people generally do not see what they are looking directly at when they are attending to something else (Mack & Rock, 1998). Neisser (1979) first reported this phenomenon by using a selective looking task to explore the role of attention in the detection of unexpected events. The most famous example of inattentional blindness came from the Invisible Gorilla experiment (Simons & Chabris, 1999). They asked a group of students to watch a video of a group of basketball players passing the ball to each other. The students were instructed to count how many passes were made during a certain period of time. After 35 seconds, a man in a gorilla suit ran into the field of players, beat his chest, and ran out of the room. When the researchers asked the students whether they saw a gorilla, 50% answered no.
The inattentional blindness plays an important role in our lives in driving safety. It is because driving is a constant attentionally demanding task and not paying attention because of engagement in other tasks can have disastrous consequences. Strayer & Drews (2007) revealed that talking on a cell phone dramatically increases the probability of missing an unexpected object due to diversion of attention from driving to the cell-phone conversation.
In this experiment, we want to explore whether the difficulty of the task increases the probability that people will miss the unexpected object.
Methods
Participants and Design
A total of 283 healthy undergraduate students from the University of Birmingham participated in this study. The experiment will involve a total of four trials in two groups. The first group was called the Group A and the second group was called the Group B. 138 students and 145 students were randomly assigned into Group A and Group B respectively. Each group of trials will involve a non-critical trial followed by a critical trial. The only difference between the two groups of trials is in the instructions given to participants.
Our independent variable is the condition under which participants watch the video and it has two levels: one is simply counting the total numbers of bounces made by the attended object (easy task); a second is separate counting of vertical and horizontal bounces made by the attended object (hard task). Our dependent variable is whether or not participants noticed the unexpected object i.e. black monkey. Our hypothesis is that the difficulty of the task increases the probability that people will miss the unexpected object.
Stimulus Material and Procedure
The stimuli for this experiment were created to Windows Media Video (WMV) file format. The first video was called the non-critical stimulus. The stimulus was presented in a 10-second video consisting of a white object and five black objects, all surrounding by a grey square. Each object moved independently on random paths and bounced the boundaries of the box. All the objects could overlap with other moving objects in the box as they passed.
The purpose of the first video is to allow participants to be familiar with the task, so the first trial contained no unexpected object, i.e. black monkey.
The second video was the critical stimulus. It was identical to the non-critical one with one exception: the black monkey. Approximately 3 seconds into the second trial (the "critical trial"), the black monkey moved slowly and horizontally in a linear path from right to left, and exited the left side of the box. The monkey was on the screen for 4 seconds approximately. During this period, all the objects and the monkey could overlap with each other in the box. Figure 1 shows the sequences of events in critical trial.
Figure 1. The sequences of events in critical trial
All participants were tested individually and gave informed consent in advance. On the experiment days, participants entered the computer lab and seated in front of a computer and they were told what to do by an instructor. Before the videos were shown, participants were told that they will be watching two videos in which five black objects and one white object moving randomly in a box and they should pay attention to the white object. Group A were asked to do the easy task, which required them to count the total number of times that the white object bounced off the boundaries of the box and Group B did the hard task, which required them to count the number of times that the white object bounced the horizontal boundaries (top and bottom) and vertical boundaries (left + right) separately.
When the participants finished watching the first video, they were asked to watch the second video, the critical one. After seeing the second video, we will examine the dependent variable – whether or not they noticed the black monkey. We will each collect data from the participants by asking them three questions: (1) ’Did you notice anything unusual during the second video, which was different from the first video?’; (2) ‘Did you notice anything unusual occurring in the background during the second video, other than the black objects?’ and (3) ‘Did you see a black monkey passing through the screen on the last trial?’. Participants answered each question in sequence and were not allowed to see any question before answering the previous ones. We will count the participants as having perceived the monkey if they answered ‘yes’ to the last question. Lastly, the participants were debriefed. We might let them watch the video again because they will probably want to see it if they have failed to notice the monkey. Each testing session lasted 5-10 min.
Results
Out of all 283 participants across all conditions, 139 (49.1%) participants saw the black monkey and 144 (50.9%) failed to see the unexpected object (i.e. monkey). Not surprisingly, noticing rates were higher in the Group A (Easy Task). This means more participants saw the monkey in the Group A (58.7%) than in the Group B (Hard Task) (40%) condition, which means that 60 out of every 100 participants failed to see the monkey right in front of them. Figure 2 shows the results for each group in the critical trial.
Figure 2: Percentage of participants noticing monkey in the critical trial
In other words, when participants were engaged in a more attentionally demanding counting task (Hard Task), more than half the participants (60%) in Group B failed to see a distinctive but unexpected monkey that appeared right on the screen for 3 seconds. In contrast, the object was almost always detected when participants were engaged in a less attentionally demanding task. This failure is what is called inattentional blindness.
The result is likely for two reasons. First, the instructions in Hard Task trials direct the observer to focus entirely on separate counting vertical and horizontal bounces. As a result, there was no attention left to process the unexpected object, and this demonstrates that seeing something requires attending to it. In contrast, in the Easy Task condition the participant could allocate some attention throughout the display, and this allows her/him to process and see the unexpected object presented in the critical trial.
Discussion
The results of the experiment confirmed our hypothesis that the demands of the difficulty of the task increases the probability that people will miss the unexpected object. These findings of inattentional blindness for an unexpected, dynamic object is also consistent with Simons and Chabris (1999) original findings that more difficult tasks leading to less noticing of unexpected objects. These findings also support the conclusion from work (Simons & Chabris, 1999) that inattentional blindness can occur for sustained and highly salient events, provided that observers are engaged in a selective-looking task.
However, this experiment did not explore certain factors that can affect inattentional blindness. One factor is visual similarity as it plays an important role. Future studies could examine the effect of visual similarity by using white monkey instead of black, which is the same colour as the attended white object. It is because many studies found that the similarity of an unexpected object to other objects, in particular the attended objects, in the display influences attentional capture. This means the more similar an unexpected object is to the attended objects, and the more likely people will see it (Most, Simons, Scholl, Jimenez, Clifford & Chabris, 2001).
Moreover, the effect of individual differences have not been examined in the experiment as it could contribute to inattentional blindness. Simons & Jensen (2009) revealed that individual differences in the ability to complete a primary task may play a role in the noticing of unexpected objects as it would influence how committed the participants are to perform well in the task.
In conclusion, our study shows that the task difficulty influences the rate of inattentional blindness. Other factors like visual similarity play a role in conjunction to influence inattentional blindness rates under sustained and dynamic conditions. The more our attention is occupied by one task, the less likely we are to see the salient events in our environment.
References
Most, S. B., Simons, D. J., Scholl, B. J., Jimenez, R., Clifford, E., & Chabris, C. F. (2001). HOW NOT TO BE SEEN: The Contribution of Similarity and Selective Ignoring to Sustained Inattentional Blindness. Psychological Science, 12(1), 9-17.
Simons D. J. (2000). Attentional capture and inattentional blindness. Trends in Cognitive Sciences, 4, 14-155.
Simons D. J., & Chabris, C. F. (1999). Gorillas in our midst: sustained inattentional blindness for dynamic event. Perception, 28, 1059-1074.
Simons, D. J., & Jensen, M. S. (2009). The effects of individual differences and task difficulty on inattentional blindness. Psychonomic Bulletin & Review, 16, 398-403.
Strayer, D. L., & Drews, F. A. (2007). Cell-phone-induced driver distraction. Current Directions in Psychological Science, 16(3), 128-131.