BecharaST1 Specs

Overall: This is a single-task experiment closely related to BecharaPRP1. However, this involves gambling without any other task. There are some other notable differences: (1) this program should keep track of RT not only for making the gamble task response, but also for "digesting" the feedback and deciding when to go on to the next trial; (2) when the subject rejects a card, they are still shown what card they would have gotten had they accepted the card; (3) we randomize the assignment of colors to the three different payoff decks, rather than having a fixed assignment.

Overview

 The task requires the subject to freely choose whether to accept a gamble.  The stimulus is a "card" shown by the computer, drawn from an imaginary "deck of cards".

Overall Procedure

1. Overall Instructions

2. 10 Blocks (each 40 trials) (with Rest between blocks)

[Between each block display subjects total winnings and their winnings in the block just completed]

Materials and Procedure for the Tasks

Design.  Subjects are not assigned to different order or subject conditions. 

Payoffs with the Task-2 Decks

Deck A offers the following:

Prob=2/3:       4 cents

Prob =1/3:      Lose 1 cent

Deck B offers the following:

Prob=1/4        20 cents

Prob=1/2        nothing

Prob =1/4       Lose 10 cents

Deck C offers the following

Prob=1/4        Lose 20 cents

Prob=1/2        nothing

Prob =1/4       10 cents

Instructions to the Subject

Overall Instructions:

Welcome to our experiment. 

The task today is what we call the gamble task.  We call this the "gamble task" because it involves prizes, but it is not really gambling, because you can't lose money here today. In the gamble task, you will be offered the chance to accept or reject a card shown on the screen.  You make your response by pressing the key labeled ACCEPT or the key labeled REJECT. 

During the experiment, you should keep the index and middle fingers of your right hand resting on these two keys. You should also keep the index finger of your left hand resting on the Space Bar, because this is the key you will press to tell the computer when you are ready to advance to the next Gamble offer.

[click to continue;  then go to new page]

Whether you accept or reject a card, the computer will flip it over, and then you'll see whether you won or lost money.  For example, if you reject the card it might say “would have lost 10 cents” or “would have won 1 cent”. If you accept the card it might say “lose 10 cents” or “win 1 cent”, and that amount will be added to (or subtracted from) your total winnings.

The money is not make-believe! At the end of the experiment, you will be paid whatever total bonus money you have earned (if by chance your bonus earnings end up below zero--which is not likely to happen--you won't have to pay us anything, of course).

The cards are colored red, yellow, and blue.  They come from a deck of cards of that color: the red deck, the yellow deck, and the blue deck.  Each of the three decks has a different proportion of win and loss cards.  Thus, you may learn that it is smarter to accept some color(s) than other color(s).  It will up to you to figure this out as best you can.

[click to continue;  then go to new page]

If you make clever selections, you will maximize your profits, although there is always a random element to this game.

Your main goal in the gamble task is to choose whether to accept the card or not, but you don't want to take too long to respond.  To give you an incentive to be reasonably promptly, we are offering a bonus for not taking too much time to respond.  You will receive a reward of 5 cents for every tenth-of-a-second faster your average relative to a baseline of 2.0 seconds.   That means that you make a bit more money if you always respond fairly promptly, but speed is not as important here as picking the right cards.

When the computer shows you how much money you won or lost (or how much you would have won or lost had you taken the card), it will wait for you to press the space bar with your left hand, and then it will go on to the next trial.

Please place your right-hand fingers on the ACCEPT and REJECT keys, and the index finger of your left hand on the space bar.

PRESS SPACE BAR TO BEGIN EXPERIMENT

[click to start]

Events on Each Block

Present fixation point (plus sign in the middle) for 1000 msec, then take it away for 500 msec, then put up a the first card.  The card remains present until the subject responds by either accepting or rejecting the card (right hand response).  Record RT measured from the onset of the card.  Whether they accept or reject, put up the message about whether they won or lost. This stays up until the subject presses the space bar to continue. Record RT spent looking at the winning/loss message.

Note that the card should not say "You won…" or "You lost…" because sometimes you are showing the card after they didn't accept it. Have it say, e.g., "Results on this Card: Lose 20 cents"

Data Handling In raw data file, save everything that happened on every trial:

<Block, trial, card color, accept/reject, potential win/loss on the card, RT to accept or reject, RT to proceed to next trial>