This protocol features three experimental techniques that can be used independently or in combination to examine questions related to psychological stress, learning strategies, and the intricate nature of episodic memory. This protocol provides researchers with a flexible template. The three methodological techniques that are brought together in this protocol can be easily adapted to answer a variety of research questions.
Demonstrating the procedure will be Grace Elliott and Dalit Hendel, senior research coordinators at the Center for Applied Brain and Cognitive Sciences at Tufts University. Begin this procedure with participant recruitment, screening, and scheduling as described in the text protocol. Randomly assign participants to either learning group, study practice, or retrieval practice.
When participants arrive to the lab, first instruct them to sit at separate desks. To begin the encoding procedure, instruct participants that they will be presented with a series of words that they must try to remember for a later test. Present participants with either the red list or the blue list, using the stimulus presentation software and rate of presentation outlined in the text protocol.
To clear working memory between each study event, have participants complete simple math problems for 30 seconds. Either have participants complete this task with pencil and paper or embed the task into the computer program used for stimulus presentation. For participants in the study practice group, present the same list two more times at the same rate of presentation.
For participants in the retrieval practice group, give them two time matched free recall tests. Prior to the two tests, instruct participants that they should recall as many words as possible from the preceding list in any order. During free recall, either have participants type their responses using the stimulus presentation software program or have them write their responses on a sheet of paper.
To clear working memory, have participants complete simple math problems between initial presentation of the word list and the first test, as well as between the two free recall tests. Next, present all participants with a 30-minute clip from an emotionally neutral movie or television show. This 30-minute delay helps establish a temporal distinction between learning the red list and learning the blue list.
Now, repeat the encoding procedure for the list that was not presented prior to the 30-minute break. Have participants complete a first iteration of the State-Trait Inventory for Cognitive and Somatic Anxiety, or STICSA, to determine whether study practice and retrieval practice differentially influenced anxiety levels. Instruct participants to fill out a second STICSA as a pre-stress measure of subjective anxiety.
Also, instruct participants to provide the first saliva sample as described in the text protocol. Administer one of the two memory tests described in the text protocol. To induce stress, begin with speech preparation.
Give both participants a sheet of blank paper and a pen or a pencil. Then instruct the participants that they will now have two minutes to prepare a speech in which they are applying for a job as a teaching assistant in any course of their choice. Tell the participants that they must be prepared to discuss what skills and experience they have that make them a qualified candidate for the job.
Use a stopwatch or clock to time the two minute period. Setup a video camera on a tripod while participants are preparing their speeches. Take participant's notes away when two minutes have passed.
For speech delivery, instruct the participants that they have each been assigned a number on their desk. Tell them that upon hearing their number, they will stand and give their speech. Direct participants to the center of the room where they can be recorded by the camera.
Explain that the video is recorded for the purpose of coding their non-verbal behavior at a later time. Call on participants one at a time to stand up and deliver their speeches. Use a stopwatch or a clock to ensure that each speech lasts for two minutes.
If a participant finishes the speech early, tell them that they still have time left and they must continue. For oral subtraction, instruct the participants that they will be called on at random to solve simple math subtraction problems. Tell the participants that when called on, they are to stand and solve the problem aloud.
If the answer is wrong, they will be asked to try again until the answer is correct. Remind the participants that they will be videotaped during this part of the experiment. Call on participants randomly and unpredictably, which means sometimes sequentially.
The participants solve math problems multiple times each for a period of six minutes. Math problems involve subtracting a number in the teens from a four digit number. When participants give an incorrect answer, tell them that they are incorrect and ask them to try again.
Repeat the question, if necessary. To complete the stress induction procedure, instruct participants to complete the third STICSA as a post-stress measure of subjective anxiety. Then, instruct participants to provide the second saliva sample.
Give participants a 10 minute break. In the present protocol, participants watched part of an episode of The Office during this break. Instruct participants to provide the third saliva sample.
Then administer the second memory test. Finally, debrief participants about the purpose of the experiment and excuse them. Compute dependent measures as described in the text protocol.
The modified version of the Trier Social Stress Test for groups used in the present protocol effectively induced both psychological stress and physiological stress. Participants demonstrated post-stress increases in STICSA scores and cortisol levels. Participants demonstrated marked increases in cortisol from baseline to 25 minutes post-stress and from 12 minutes post-stress to 25 minutes post-stress.
Cortisol levels did not significantly increase from baseline to 12 minutes post-stress. The retrieval practice group also demonstrated the lowest false alarm proportions, but only for the post-stress test. In contrast, source memory was unaffected by stress.
Individuals in the retrieval practice group demonstrated chance level performance. Who, what, when, where, why and how are the contextual elements of episodic memories. This protocol examined the what and the when by presenting lists that were segregated by color and time.
This paradigm could be used to explore other contextual elements of memory. For example, researchers could examine the where component by changing the physical location in which the word lists are learned.
