Why we need links

Imagine that we get hold of ten people to do our experiment. We send them each the URL for our Qualtrics questionnaire about age, and the URL for our Pavlovia experiment about reaction times. We want to combine these sources of information so that we have a single file for each person that includes their age and their response times. In order to do that, each person needs to have the same ID number on each system. We could tell each person before they start what their id number is and ask them to enter it on each system, but this would represent a lot of work for us – we would have to communicate with each participant after they agreed to participate and before they started, to tell them their ID number, and we would have to make sure that everyone received a separate ID number. We would also be relying on them not to make any mistakes when entering their number; and we would have to keep track of whether they completed the task so we could award course credit or a voucher only to those who completed the task.

The alternative is to take advantage of the fact that Qualtrics, SONA, Pavlovia etc have ways of generating a unique ID number for each participant and passing them around to each other so that the same participant has the same ID number on each system automatically, and so that when the participant has finished, a message can be sent to SONA or whatever remuneration website you are using to pay people when they have completed their participation. The way that the websites communicate with each other is by generating custom links that encode the participant’s ID number.

So long as you know which website is sending the link, and which website is receiving the link, the information in this guide will tell you how to specify a link between the sending and receiving websites that encodes the ID number.