EmRSVP2

General Overview: Subjects perform a speeded numerical judgment task on digit pairs, attempting to ignore any other visual stimuli. Then a sequence of 5 pictures is presented (one of them is sometimes a negative emotional picture) and the subject is suddenly asked through the speakers to type in a brief description of these pictures. They type it in using a text box.

Summary of Procedure. In block 1 subjects practice parity judgment task (25 trials). In block 2, subjects perform parity judgment task (25 trials) while ignoring occasional intrusions of visual stimuli. In block 3, subjects perform parity judgment task for 5 trials and then see the 5 pictures flashed at a rate of 250 msec per picture. Then they see one more digit, respond to that digit, one more digit, respond to that digit, and then suddenly through the computer speakers a voice tells them to describe as many of the pictures you just saw as they can. After each instruction screen, subjects see a message for 4 seconds saying "Please place fingers on keys and look in the center".  That message is taken away for 1 second, and then the digits are displayed.

Parity Judgment Task. On each trial, randomly select two digits (leftdigit and rightdigit) in the range 2,…,9. If the two digits are identical, replace them with two new digits. The two digits should be presented in very large font to the left and right of fixation (large enough so you can do the task while keeping your eye in the center of the screen). They should appear for 200 msec and then disappear. Correct response is based on whether parity of the digits mask. Response keys are Z for “same” and / for “different”. E.g., for the digits 4 9 the response would be to hit the Z key.

Variables

Subject Condition typed in by experimenter. This determines the composition of the 5 pictures:

Condition Sequence

1 Neut, Neut, Emot, Neut, Neut

2 Neut, Neut, Neut, Emot, Neut

3 Neut, Neut, Neut, Neut, Neut

Picture Selection

Use the list of 48 neutral pictures and 10 emotional pictures from the IAPS whose filenames are appended below. Randomly select pictures without replacement from the list. (E.g., if a subject is in condition 2, you randomly select 4 pictures from the list of neutral pictures, and randomly choose one emotional picture from the list of emotional pictures. The order is as shown: 3 neutral, then the emotional, then a final neutral picture)

Detailed Procedure

First Screen: Ask experimenter for subject number, subject condition, and remind experimenter of the response mapping for the parity judgment task in case they have forgotten to label the response keys.

Instruction Screen 1: Thank you for participating in our experiment. We are looking to see how well you can ignore visual stimuli that you are looking directly at. Your basic task will be this: you see two digits, and you determine whether they are the same in “parity” (odd vs. even). Thus, the digits 3 and 5 are both odd, so they have the same parity. The digits 2 and 9 are different parity, so if you see these digits you would say “different”.

Instruction Screen 2: Let’s try 25 trials so you can get used to this task. Please look directly in the center of the screen throughout each block of trials (a plus sign will show you where to look). Please keep your fingers rested on the two response keys marked Same and Different, and respond as quickly and accurately as you can.

Block 1. In Block 1, they simply perform the task. The procedure is diagrammed here:

Then present further instructions:

Instruction Screen 3: Good job. You made ___ errors, and your average response time was ______ milliseconds. Now we will see how well you can ignore some visual stimuli presented in the middle of the time you are doing this task. Things will flash on the screen, but you should just keep looking in the center and waiting for your next digits to appear. As soon as the digits appear, respond as quickly and accurately as you can. If at any time you hear additional instructions presented through the computer speakers, please follow these instructions.

Block 2 consists of 25 more trials. However, immediately after the subject responds to trial 8, present a large red square in the center of the screen for 250 msec, followed by a large green disk for 250 msec. Then immediately present the next pair of digits.

At the end of trial 19, do the same thing, using three different colored shapes.

Instruction Screen 3: Good job. You made ___ errors, and your average response time was ______ milliseconds. In the next block, we will look at your ability to ignore other kinds of stimuli. Just try to respond as quickly and accurately as you can. If at any time you hear additional instructions presented through the computer speakers, please follow these instructions.

Block 3 consists of 7 more trials. Immediately after the subject responds to digit trial 5, present the five pictures in succession in the middle of the screen. Each picture should be presented for 250 msec. Then immediately present the next pair of digits (trial 6) and the next one (trial 7). As soon as the subject responds to trial 7 digits, play the message through the speakers. The message should say in a quick and clear way:

RT

9 5

“Please type in a description of the pictures you just saw. One phrase per picture is fine.”

Put up text box and let the subject input descriptions. When they are done

We are done now.  Thank you very much for participating in our study.  We are looking at incidental memory for pictures perceived while doing another task.  If you talk to anyone else who may be participating in this study, please do not tell them about the experiment, ok? Let them click Yes or No. Leave that up on the screen and close down study.

Data Storage Store everything, including which digits were presented, what the RTs were, what the correct response would be, etc. Make two files, Rd-x and Rp-x. Rd-x contains a record of performance on every trial of the digits task. Rp-x stores what pictures were presented, and how the subject described these pictures.

For Rd-x, the format should be one row per trial, with columns containing subject number, condition for that subject, block number, trial number, digits presented, correct response, actual response, and RT.

For Rp-x, the format should be: row 1 = subject number; row 2 = condition number; rows 3,4,5,6,7 = codes for the 5 pictures presented; remainder = subject’s typed in responses.