양분 청취법
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Overview
출처: 조나단 플롬바움 연구소 -존스 홉킨스 대학
들어오는 자극을 처리하는 인간의 능력이 제한적이라는 것은 잘 알려진 사실이다. 그럼에도 불구하고 세상은 복잡하며, 항상 많은 일들이 한 번에 일어나고 있습니다. 선택적 주의는 인간과 다른 동물이 어떤 자극이 처리되고 무시되는지 제어 할 수있는 메커니즘입니다. 칵테일 파티를 생각해 보십시오: 한 번에 일어나는 모든 대화에 참석할 수 없었던 사람이 있을 것입니다. 그러나 모든 사람은 한 대화를 선택적으로 들을 수 있으며, 나머지는 모두 무인으로 이어지며 배경 소음에 지나지 않습니다. 사람들이 이 작업을 수행하는 방법을 연구하기 위해, 연구원은 각 귀에 동시에 다른 소리를 재생하여, 즉,dichotically 참가자에게 소리를 재생하여 더 제어 칵테일 파티 환경을 시뮬레이션합니다. 이를 이분적 듣기 패러다임이라고 합니다.
이 실험은 이분멸 듣기라는 패러다임으로 선택적 청각주의를 조사하기위한 표준 절차를 보여줍니다.
Procedure
Results
The graph in Figure 1 shows the percent of questions answered correctly by condition. The red dotted line (at 20%) shows expected guessing performance (chance), given that each question included five choices. The participant was able to answer more questions correctly for the attended compared to the unattended passage, reflecting the ability to attend selectively to a single stimulus when more than one is present. But the participant also answered more questions correctly in the one passage baseline condition compared to the attended condition. This demonstrates the difficulty of attending selectively, and the limited capacity of human attention.
Figure 1. Results from dichotic listening experiment. Shown are the percent of questions answered correctly by condition.
Applications and Summary
Dichotic listening has been used for many purposes to understand the nature and capacities of selective attention. For example, it has been used with a concurrent visual task to investigate the extent to which visual and auditory attention compete with one another—an important issue for understanding when and how humans are able to multitask.
One of the most influential applications of the paradigm has been in the study of the human brain’s lateralization for processing language. The human brain is divided into two hemispheres. Generally speaking, the right hemisphere is wired to the left side of the body, and the left hemisphere is wired to the right. This means that auditory stimuli played exclusively to one ear will be routed, first, to the opposite brain hemisphere. It is also known that the left hemisphere is generally specialized for language processing. Therefore, the prediction is that stimuli played to the right ear should be processed more effectively than stimuli played to the left ear. This has been confirmed in many dichotic listening studies, and it makes dichotic listening a useful paradigm for investigating language deficits thought to be associated with left hemisphere brain damage, as often occurs after a stroke, but without using a brain scan.
Transcript
Dichotic listening is a paradigm used to characterize the nature and capacities of selective attention.
Selective attention is the mechanism that allows humans and other animals to control which stimuli are processed and which are ignored.
For instance, think of a cocktail party where there are many conversations taking place at once. An individual can focus their attention to listen to only one conversation, which will lead the rest to become nothing more than background noise.
This video demonstrates a dichotic listening paradigm, which involves playing different auditory stimuli simultaneously to each ear. You will learn how to design and perform, as well as how to analyze and interpret an experiment investigating selective auditory attention.
During this experiment, participants complete two listening sessions: the first measures baseline listening comprehension, and the second involves dichotic listening. Participants are asked to pay attention and listen carefully.
For the baseline session, a single passage is played through the headphone attached to the right ear. Nothing is played in the left ear.
During the dichotic listening session, one passage is played through the right ear, and a different passage is played simultaneously in the left ear. Participants are asked to only attend to the passage played in their right ear.
After each session, participants are given a set of comprehension questions that are associated with the recorded passages. In this case, the dependent variable is the number of comprehension questions answered correctly after each passage.
Participants are expected to answer more answers correctly for the attended passage compared to the unattended passage.
To create the stimuli for the experiment, select three different passages with information content that can be tested for comprehension. Record one person reading the selected pieces. Make sure to save each recording into individual audio files.
In relation to the passages, you will need two sets of headphones connected to the audio source to easily play separate auditory clips, and printed copies of the comprehension questions for the participant to complete after the listening sessions.
To begin the study, inform the participant that they will put on headphones to hear a short passage delivered to their right ear. Instruct the participant to pay attention and listen carefully, as they must answer questions about the passage afterwards.
After the participant puts on the headphones, play one of the passages through the side attached to the right ear. Note that nothing is played through the left ear.
Once the passage has finished playing, have the subject remove the headphones and give them a set of associated questions. Allow them 15 min to answer as many as possible.
To initiate the dichotic session, inform the participant that they will put on the headphones again, but will hear two different passages played simultaneously in each ear.
This time, instruct the participant to pay close attention to the passage in one ear and ignore the reading in their other ear. Press play at the same time to start the two different passages in each ear.
When the recordings are over, ask the participant to answer questions from both passages—the attended and unattended—within 30 min.
After the participant has finished answering the questions, score the answers as being correct or incorrect.
To analyze the data, calculate the proportion of correct answers associated with each individual passage. Graph the average percent correct by passage.
When selective attention was required, participants’ performances declined, but they answered more questions correctly for the attended compared to the unattended passage. These findings demonstrate the difficulty of selectively attending to stimuli—that a limited capacity of attention exists.
Now that you are familiar with how dichotic listening is used to study selective attention, let’s take a look at how this method is applied in other research studies.
The dichotic listening task is a very useful paradigm for evaluating language deficits associated with brain damage, such as after a stroke.
Generally speaking, the right hemisphere is wired to the left side of the body, and the left hemisphere is wired to the right. Such connections mean that auditory stimuli played exclusively to one ear will first be routed to the opposite brain hemisphere.
Given that the left hemisphere is specialized for language processing, auditory stimuli played to the right ear should be processed more effectively than stimuli played to the left ear. Thus, this paradigm can assess brain damage without the use of a brain scan.
Dichotic listening can also be combined with simultaneous tactile stimuli to study how the brain integrates multisensory information—an important issue for understanding when and how humans are able to multitask.
You’ve just watched JoVE’s introduction to investigating selective attention through a dichotic listening paradigm. Now you should have a good understanding of how to design and conduct this type of study, and how to analyze and interpret the results.
Thanks for watching!