Pslack1

TrainType2

On every trial, you present a single letter randomly and independently drawn from a set of 6 letters. There are six possible response keys <ZXC,./>. The mapping is the same for every subject:

LETTER RESPONSE KEY

K Z

V X

D C

S ,

B .

G /

The letter should be large (say, 18 point font) in the center of the screen. It should remain present until the subject responds, and then it disappears. Response-stimulus interval (from keypress to next response) should be a random number between 1 second and 2 seconds. (Save what it was!)

There should be 32 blocks of 20 trials. Again, on every trial you just randomly select a letter; that automatically determines the correct response.

You should ask the experimenter for initials, subject number, and whether the subject is in Subject_Condition 1 or 2 or 3 or 4. Subject_Condition determines how the letters are selected in the first 16 blocks

Subject_Condition 1: Randomly select the letter independently on each trial in all of the 32 blocks, so there is a 1 in 6 chance of each letter being presented independent of whatever happened before.

Subject_Condition 2: In Blocks 1-8: On the first trial in blocks 1-16, select the letter randomly. For all the remaining trials in that block, the letter should repeat what was presented on the previous trial with prob=0.85; with probability 0.15 it should be different (0.03 chance of each of the other 5 lettters). In Blocks 17-32: choose letters randomly and independently just as in Condition 1.

Subject_Condition 3: In each of blocks 1-16, you always present just one of the letters. Tell the subject at the beginning of the trial “please keep all six response fingers rested on the keys throughout this block; we will only be training on one letter”. The letter should rotate, so that each of the six letters is used in two separate blocks out of the first 8 blocks. In Blocks 17-32: choose letters randomly and independently just as in Condition 1.

Subject_Condition 4: In each of blocks 1-16, you randomly and independently select a letter just like you do in Condition 1. However, you tell the subject right before each trial what the proper response will be. E.g.: “Prepare to make Response 4” if the next stimulus will be an S. This message should stay up there for 1 second prior to the appearance of the stimulus. In Blocks 17-32: choose letters randomly and independently just as in Condition 1.

Let’s present instructions within the program.

Welcome to our experiment. We are looking at how fast you can respond to letters by pressing a button. On every trial, you will see one of six possible letters. There are six response keys marked on the lower row of the keyboard. You should rest your index and middle fingers of your left and right hands comfortably on these response keys when the experiment begins. Please keep them there while the experiment is running.

There are six possible letters. For each response key, there is one letter corresponding to that response. The assignment is like this

K V D S B G

So if you see an K, you would press the leftmost key. If you see a B, you would press the second key from the right.

We will do 32 blocks of trials. Each block will last just a little over a minute. At the end of a block, there will be a rest period. Take a minute to relax, and then when you’re ready to resume, just press one of the response keys and the experiment will begin. The six letters will sit at the bottom of the screen to help you learn which keys go with which letters. You can check them if you need to, but please try to keep your eye in the center of the screen (this is where the letters you need to respond to will appear).

Please try to respond as rapidly and accurately as possible. If you have any questions, ask the experimenter now. We appreciate your participation and hope you find this task at least somewhat entertaining. Just concentrate on trying to do your best and we will be finished before you know it.

Each display should look something like this, with the eight letters just sitting there throughout the experiment.

S

K V D S B G

Timing

When the subject presses a key to start a block, wait 1.5 seconds, then put up a plus sign in the middle for 1 second, then take that away for 500 msec, then put up the first letter. Each letter should always remain present until the subject responds. As soon as the subject responds, the letter should disappear. The next letter should appear after the randomly chosen intertribal interval (1000 msec – 2000 msec). During this intertrial interval, there should be nothing on the screen.

End of Block

At the end of the block, put up a sign that says REST PERIOD – PLEASE REST AT LEAST 10 SECONDS. Also display the subject’s mean response time and number of errors from each of the previous blocks. That way the subject can track their improvement (and they will improve a lot). This makes it more motivating to the subject. Make them rest 10 seconds before you put up PRESS ANY KEY WHEN YOU ARE READY TO RESUME.

Data Analysis

The raw data file should contain

When you make the Sfile, blocks should be a factor. So the Sfile should have these factors: