Dichotic Listening

1. Apparatus and stimuli

1. Use two sets of headphones and two pieces of hardware for playing auditory stimuli. Ultimately, the experiment requires the ability to play two separate auditory signals through separate headphones. This can be done with a sound mixer or with a computer. But it can be done easily and without technical expertise by using two separate pieces of hardware.
2. Select three different recordings with informational content that can be tested for comprehension. These recordings are the stimuli for dichotic listening. Comprehension questions are also necessary.
   1. A good source for this kind of material is publicly available reading comprehension texts and questions from exams like the Scholastic Aptitude Test. For this demonstration, two pieces of text and their associated questions selected can be found in Appendix 1.
3. Record one person reading each of the selected pieces, and create three individual audio files.
4. Print out the questions for each passage for the participant to complete after hearing the relevant recordings.

2. Procedure

1. Keep in mind that the goal of this experiment is to compare the ability to retain information for selectively attended stimuli compared to unattended stimuli. Set up the experiment to include two listening and test sessions.
   1. The first session is a baseline, with only a single audio passage intended to measure baseline listening comprehension without a second stimulus present.
   2. The second session involves two different passages played simultaneously, one to each ear, with instructions to attend to one of them.
2. Explain the instructions for the baseline condition to the participant, as follows:
   1. “In a moment, I will ask you to put one headphone in each of your ears. I will press play, and a short passage will be read aloud to you through the headphone in your right ear. Nothing will come from the other. Please pay attention and listen carefully while the passage is read. Afterwards, you will be asked to answer some questions about the passage.”
3. Play one of the passages through the headphone attached to the right ear. For control purposes, the participant should have a headphone in the left ear as well, but nothing should play through it.
4. Once the passage has finished playing, give the participant the set of questions associated with it, and allow them 15 min to answer as many as possible.
5. For the dichotic condition, explain the procedure to the participant, as follows:
   1. “In a moment, I will ask you to place a headphone in each of your ears again. And again, a passage will be read aloud through the headphone played to your right ear. Please play close attention to that passage because you will be asked questions about it after. But this time, a different passage will be read aloud through the headphone in your left ear. You should do your best to ignore that passage, and direct your attention to your right ear.”
6. Once the participant has the headphones placed in their ears, press play simultaneously on each.
7. When the passages are done, give the participant the questions for the two passages. They should be in the same document and randomly intermixed. Explain this to the participant:
   1. “Now, I’d like you to answer as many questions as you can about the passages you just heard. About half of the questions are from the passage I asked you to pay attention to. But the other half will be from the other passage. Please do your best. And if you feel like you don’t know an answer, just guess.”
8. Allow 30 min for the participant to answer the questions. Once the participant has left, score the answers.
9. Once the questions are scored, calculate the proportion correct associated with each individual passage. Graph the scores.