Physiological effects of sound when watching terrorist attacks

This topic submitted by Marissa Grier, Adam Haigh, Susie Quilligan, Aaron Schielke ( at 11:39 am on 12/11/01. Additions were last made on Wednesday, May 7, 2014. Section: Myers

Discovery Lab Report

In our experiment, we will study the physiological affects of sound in terrorists and other attacks on individuals. We will monitor the heart rate of a total of about 30 people as they watch a 12-minute video of different attacks. First a 2-minute clip will play with no sound, and then the next clip will play with a form of sound such as music, speech, or action (bombing) sounds. We will be sure that the sound clips that accompany the video clips are unrelated (independent) of the content of the video that is used.

Our hypothesis is that if we test numerous amounts of people using our 12-minute clip of terrorist attacks, that we will find a significant variance in the amount of stress if the sound is present then when the sound is not. To find this we will measure the heart rate of each individual. According to out predictions, when the sound is present the heart rate will go through a noticeable change. The different types of sounds will help to determine which audio affects the physiological signs of stress the most. To do this, we will use 3 different sound clips within the 12-minute video. This will allow us to gain a general perspective of which sound affects the signs of physical stress the most. The clips will be the same in length to reduce variability and the same exact clip without sound will follow each clip with no sound. This also allows variability to be reduced.

In developing our methods, we referred to previous studies that examined the physiological reactions of viewers to filmed violence.
Shintaro and Fujio (1998) studied the effects of filmed violence on viewer’s affect, thoughts, and physiological reactions. Eighty normal male and female Japanese adults (aged 18-25 years old) viewed 1 of 4 violent films with rated levels of violence and entertainment. Immediately afterwards, the subjects described their thoughts during film viewing, and they rated their affective reactions towards the film. Heart rate and eye-blink rate were measured continuously before, during, and after film viewing. This study is relevant to our experiment in a few areas. First, we will be measuring the physiological effects that viewed violence has on an individual. Both this study and our experiment will be dealing with subjects in the same age range. Finally, we will draw from Shintaro and Fujio’s method of measuring of heart rate, as the main physiological factor.
In her study, Titus (1999) had subjects fill out a questionnaire assessing various personal traits and their beliefs about aggression. All subjects then viewed three film clips: a provocation clip, a violent clip, and a “justified” violent clip. After each clip, the subjects filled out a questionnaire asking them to rate specific emotional reactions (e.g., anger, anxiety, amusement). Physiological responses (heart rate, skin conductance, and finger temperature) and facial expressions were recorded throughout the film viewing. After viewing the clips, subjects filled out a questionnaire assessing their exposure to violence both in real life and in the media. Subjects were then classified as having high or low ‘anxious arousal’ in response to the violent films. The results of this study are important to our experiment in seeing what the subjects themselves believe about their exposure to violence in the media in real life. Just as Titus observed and classified the subjects as having high or low ‘anxious arousal’, we will also be observing and classifying subject’s arousal, (which is based upon the degree of increase in heart rate), as they view each of the segments that compose the entire video.
Koukounas and McCabe (2001) assessed gender differences in emotional responses to violent film. Both subjective emotional response and eye blink startle magnitude were assessed while twenty men (mean age being 22.7 years) and twenty women (mean age 30.1 years) viewed a series of five violent film segments and five nature scenes. The subjects exhibited higher levels of curiosity, anxiety, disgust, and anger, and lower levels of positive emotion and boredom, in response to the violent film segments in comparison with the nature material. Startle response was magnified during the violent film segments, indicating an aversive response. Men experiencing greater positive feelings, entertainment, and curiosity in relation to the violent film demonstrated evidence that men and woman responded to violence differently, whereas women reported more disgust, boredom, and anger, and experienced greater startle in relation to the violent scenes portrayed in the film. Our experiment will also look for a difference in the subjects’ responses to two different types of video clips (no sound versus sound). This will be similar to how this study observed subjects’ responses to violent scenes versus nature scenes. Also, we may look to this study in drawing conclusions about the different effects that it has on men versus women.
Reeves, Lang, Kim, and Tatar (1999) assessed viewer’s attention and arousal in response to three different size screens (56-inch, 13-inch, and 2-inch picture heights). Viewers responded to video images from television and film that displayed different emotions. A total of sixty video segments were shown. Attention was measured by heart rate deceleration in response to the onset of pictures, and arousal was measured by skin conductance during aggregated during viewing. This study made us aware of the effect that the screen size has on one’s response to the content that they are viewing. We will be sure to take the size of the screen being used into consideration, and make sure that it is consistent in all of the tests.

We will compile a 12-minute video, which will be divided into six 2-minute sections. In the video, the visual will be of three different terrorists attacks, each 2 minutes long, and each one will be repeated. The clips will be accompanied by segments of silence and sound. Here is a table, which shows how the audio and video are arranged:

Clip 1: Nairobi Clip 2: World Trade Center Clip 3: Oklahoma City
Silence Speech Silence Action (Bombing) Silence Music

These sounds will be unrelated to the video. We plan to test the effects of each of these audio accompaniments on the physical manifestations of stress, specifically heart rate. One concern, which we had, was that it might be the content of the video that was causing stress and not the audio. We hope to find that the addition of audio to the silent video will increase the stress under which the subjects are placed, and that music, speech, and action sounds will produce different amounts of stress for the subjects. The audio in all three of these cases will not be designed to compliment the video in any way, as to insure the stress we measure is due to the audio alone. In taking the subjects’ pulse, we will take the readings during the middle minute (from 30 seconds into the clip to 1 minute, 30seconds into the clip) of each clip. We were also concerned with subjects who may have already seen the terrorist acts that they will be watching. Therefore, there may be a kind of emotional fatigue associated with these images, which could render our test invalid. For that reason, we are planning to use a range of footage from not only these most recent terrorist acts, but also ones from around the world, and throughout the century.

Speech Sound vs. No Speech Sound, Bombing Sound vs. No Bombing Sound, and Music Sound vs. No Music Sound:
For all the sounds we had expected to find that when an audio track was introduced that we would find an increase in heart rate. This was true for the addition of speech sounds and bombing sounds, but when music sounds were added, subjects’ heart rate actually went down. The mean difference between speech and no speech was 1.280 this comparison had a significant p-value of 0.0001. The mean difference between bombing and no bombing was 1.640 this comparison had a significant p-value of 0.0001. The mean difference between music and no music was –1.400 this comparison had a slightly greater, but still significant, p-value of 0.0010.
Sound vs. Sound:
In the first bar chart, a comparison is made between the music and the bombing sounds. It shows that the bombing sounds seem to increase the heart rate more so than the music, and they also increase the heart rate more so than the speech, which is displayed on the other bar chart. The speech and the music had relatively the same heart rate, and all of them had rather insignificant p-values.
No Sound vs. No Sound:
This comparison shows how each of the three different videos affects the heart rate. From the bar chart, one can see that the visual of the World Trade Center attacks had a greater affect than that of the Nairobi attacks. However, the Oklahoma City attack had a slightly higher affect than both the World Trade Center and the Nairobi attacks.
Initial heart rate (resting pulse) vs. No Speech:
This comparison is made to show the first change that occurs to the subjects’ heart rate. The heart rate reading that was taken before the video began is labeled as the “initial” heart rate, and this is compared to the reading that was taken during the first 2-minute clip of the video, the clip of Nairobi without sound.
Male vs. Female
Here, the average increase of heart rate for the male subjects is compared with that of the female subjects. The averages of the increases in heart rate were chosen from the second clip (the increase between no sound vs. bombing sound). Looking at the bar chart, one can see that there is a dramatic difference in the effect that the sound had on males vs. females. On average, females’ heart rate experienced a 1.833 greater increase than men.

In conclusion, we proved our overall hypothesis to be correct. In our experiment, we observed that the heart rates of the subjects did increase as they viewed the video clip with no sound present, followed by the same clip with sound. We did make one observation that goes against our hypothesis. The subjects’ heart rates actually decreased during the clip that was accompanied by the music. This leads us to believe that the music had a calming effect on the subjects.
We must consider the possibility of error in our results. One thing to consider is the condition of the subjects at the time that they were tested. Also, there was a possibility for human error in our taking of the subjects’ heart rates, because we took them manually.
This experiment, and the data that we collected, leads us to think about the further possibilities for investigation in this area. With the proper equipment, other physiological signs, other than just heart rate, could be measured. These could include breathing rate, eye blink rate, or body temperature. Also, many questions can be raised about the possible considerations in examining the effects on different demographic groups. For example, one can look at the affects that race or age has on one’s response to the tests.

Emotional responses to filmed violence and the eye blink startle response: A preliminary investigation. Koukounas, Eric; McCabe, Marita P. "Journal of Interpersonal Violence" Vol 16(5) 2001 p.476-488 Saga Publications Inc, US.

The effects of media violence and aggression: Focus on the role of anger evoked by provocation. Yukawa, Shintaro; Endo, Kimihisa; Yoshida, Fujio. "Japanese Journal of Psychology" Vol 72(1) 2001 p.1-9 Japanese Psychological Assn., Japan.

The effect of media violence on aggression: Is aggressive behavior meditated by aggressive cognitions and emotions?. Yukawa, Shintaro; Yoshida, Fujio. Japanese Journal of Psychology" Vol 70 (2) 1999 p.94-103 Japanese Psychological Assn., Japan.

The effects of media violence on affective, cognitive, and physiological reactions of viewers. Yukawa, Shintaro; Yoshida, Fujio. "Japanese Journal of Psychology" Vol 69(2) 1998 p.89-96 Japanese Psychological Assn., Japan.

The effects of screen size and message content on attention and arousal. Reeves, Byron; Lang, Annie; Kim, Eun Young; Tator, Deborah. "Media Psychology" Vol 1(1) 1999 p.49-67 Lawrence Erbaum Associates, US.

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