Yoking Random Pairs
…\DirectRT\samples\6- v2006\yoking random pairs
This sample demonstrates how to present a stimulus paired with a previous stimulus, when that previous stimulus was randomly chosen. This gets around the fact that you do not know in advance what the previous stimulus was.
In the past it was difficult to randomly choose a stimulus from a list and then subsequently present a paired or matched stimulus from different list. DirectRT now makes this easy by allowing you to say "pick the item from this list that matches the position of the item I just randomly chose from that list!" Say for example, you want to use a randomly chosen prime/target pairing, where primes and targets are each in their own lists. Choose a random prime as usual by requesting $prime. Then simply ask for &target^-1. Using the & symbol you are requesting a specific item from a list. The -1 value tells DirectRT to use the position equal to the position of the last random stimulus chosen. Use greater negative values to match random picks from farther back.
On each trial in the sample input file "yoking.csv," a voice file is randomly chosen at the start of each trial. The subsequent stimuli for the trial are all chosen as a function of which voice file was chosen. Try the sample and see--e.g., if the third voice file is chosen, then the subsequent stimuli include the third behavioral description, and third question from each of the question lists.