Decision making experiment

hi everybody, I have spent a great deal of hours reading the different questions and answers of the website, and as a Matlab beginner I have learnt a lot. Unfortunately, I havent been able to find a solution for the decision-making experiment I am trying to program. A little help would be appreciated!

The task would be as follows: participants have to choose between 2 curtains (A and B). The curtain chosen is from now on 'chosen', and the other one is "alter". Behind each curtain a token is hidden. A green token indicates a gain and a red one indicates a loss. There are 4 different types of trial: # chosen=green; alter=red # chosen=red; alter=red #chosen=green; alter=green # chosen=red; alter=green I want each participant to see 40 trials of each type (that is, I m shamelessly lying to my participants who "believe" the game is random).

Each trial should go as follows (see picture of a trial here:<http://i.imgur.com/GTZIJ.png>) a)the participant is shown the 2 closed curtains and he is asked to pick one by clicking on A or B on the keyboard(1 sec) b)A bold frame appears around the chosen curtain (0.5 sec)and stays until the end of the trial c) The ALTER is opened first (2sec) and stays open til the end of the trial d) the chosen curtain is then opened (2 sec). e) Next trial starts

So here is what I have managed to come up with (in term of ideas). Since I have only 4 types of trials, I should start by giving each of my 160 trials a random number between 1 and 4. Then I should define each one my cases. For example, Case 1 in which the participant wins while the alternative is a loss should be (in words…) something like: First, show the picture with the 2 closed frames. If participant chooses A, then you want A to be framed, B to open first to show a red token, and then A to open to show a green token. If participant chooses B, then you want B to be framed, A to open first to show a red token, and then B to open to show a green token.

I guess that to make the coding job a little easier, instead of "asking" the program to switch the tokens from A to B according to the participant's choice, I could simply have a whole set of different pictures. If the trial is case 1, then I could have: pick_a_curtain.pic, then - If participant chooses A: A_is_framed.pic then B_is_red_A_closed_and_framed.pic then B_is_red_A_is_framed_and_green.pic. - On the other hand, if participant chooses B: B_is_framed.pic then A_is_red_B_closed_and_framed.pic then A_is_red_B_is_framed_and_green.pic.

I hope this is not too complicated to understand… What I need help for is to design one of my four trials (for example Case 1). I hope that I will be able from that piece of code to design the 3 other trials.

Many thanks in advance!

Deborah