Three seperate stimuli on screen at the same time: MT-IRAP attempt

[BookerJ44]

Hi,

I am attempting to emulate an experiment known as the MT-IRAP.
(here's the link to the paper that documented its creation, if needed: http://files.eric.ed.gov/fulltext/EJ913515.pdf )

Essentially, it is an experiment where participants must make one of two relational assessments ('similar' or 'opposite', via a key press for each) between two stimuli: a label stimulus (dichotomous; one of two possibilities e.g. 'good' or 'bad') and a target stimulus (one of six possibilities e.g. three positive words and three negative words), as well as a cue stimulus, indicating to the participant whether to lie or tell the truth.

What I am trying to do on Superlab is have it so that a label stimulus (in my case one of two pictures), target stimulus (one of six words) and a cue stimulus (either 'lie' or 'truth') all appear on screen at the same time, to which the participant will respond by pressing one of two keys ('l' or 'a'). I would also need it organised so that the order in which each of these three classes of stimuli are presented is randomized, and that every possible combination occurs.

I have attached my very poor attempt at doing this, and was hoping someone could advise on how to improve on my current effort, so that it achieves my goal.

Thanks in advance.

P.S. I realize that this is a lot to take in, and that the experimental design is rather complicated. Please let me know if you require any more info in order to understand and help me.

[Arman]

Your experiment is missing its media files. Next time, click File > Create an Experiment Package... in the menus.

Take a look through the attached experiment. There are three events, each using a unique stimulus list. The first two end immediately and the last two do not erase the screen. In the List Access tab of the trial, randomization is enabled and Crossed is selected. This will result in all combinations of stimulus list items to be presented.

In order to randomize the sequence, there is a counter parameter that is assigned a random value between 1 to 6. Depending on its value, the sequence of the three events are different via rules.

Let me know what the experiment is missing or if you have any questions.

[BookerJ44]

Oh sorry- I'm still learning!

The experiment you attached is great, thank you. I have made the necessary tweaks to it, but I have a few, more general questions. What do the 'end immediately' and 'erase screen' functions actually do in this context? Why are they necessary for having multiple stimuli on screen at the same time? Also, if I were to measure the time taken for each button-press, which of the events should I reset the RT timer for?

Thanks for your help so far.

[Arman]

By default, events erase the screen before being presented. For many tests, this is desired, otherwise there may be a growing clutter of text, images, etc. throughout the experiment. However, in some cases, we should disable this option, such as when we are trying to present stimuli at the same time.

When a preceding event ends immediately and the following event disables screen erasing, it is as if the stimuli were presented simultaneously because 1) both stimuli are displayed and 2) the time interval between the events is incredibly small.

As for your last question, you would reset the RT timer for the last relevant item in the event list, which is Cue Stim. Even though it does not appear so, this event will always be presented last and therefore is the one that awaits a response. The appearance of a different order upon each trial is not due to a randomization of sequence; rather, it is a result of rules and trial variables manipulating the events' positions at the end of each trial.