Using pyjamas to program external Mechanical Turk experiments

I recently set up my first external Mechanical Turk study. My greatest friend and foe in this process was pyjamas, a Python-to-Javascript compiler and Widget Set API. THE great advantage of using pyjamas: you can program your entire experiment in python, and pyjamas will create the browser-dependent javascript code. If you already know javascript, writing your experiment in python without having to worry about browser-dependent issues will save you time. And if you don’t, you don’t have to go through the frustrating process of learning javascript. On the downside, the documentation for pyjamas is currently not very good, so figuring out how to get things to work can take a while.

That’s why I’m providing the (commented) code that I generated to create my MechTurk experiment. A short demo version of the experiment can be found here.

If you find this code helpful, please consider acknowledging it via the following URL in your paper/presentation to spread the word:
https://hlplab.wordpress.com/2011/12/25/using-pyjamas-to-program-external-mechanical-turk-experiments/

A screenshot of the experiment. Participants were asked to rate on a 7-point scale how natural the statement they heard was as a description of the scene.

The structure of the experiment, which combines timed image presentation, playing audio via HTML5, recording naturalness ratings via radio buttons, and recording feedback via a text box:

1. Participants first see an instructions page with a CONTINUE button. Upon clicking CONTINUE,
2. they continue to a sound test. This is to make sure participants can actually hear sound via their speakers/headphones. They click PLAY and are asked to enter the first word of the phrase they hear. If the word is entered correctly,
3. the main body of the experiment begins. Each trial consists of
   • displaying an image of a full gumball machine, which after 1.5 seconds changes such that
   • a second image is displayed where a certain number of gumballs has moved to the lower chamber. An audio file is played (statements of the form “You got X of the gumballs”). Next to the gumball machine, a 7-point scale of radio buttons is displayed on which participants are asked to rate the naturalness of the statements they heard as a description of the scene. Below the scale, there is a FALSE button that participants are asked to click if they think the statement was false. When a button is clicked, information about which button it was is recorded and the next trial begins.
4. On the last trial, a feedback box is displayed alongside a SUBMIT button. Upon clicking SUBMIT, all the information about the experiment (worker ID, trial information, participants’ responses, etc) is submitted to Mechanical Turk. Note that in the demo version I’ve made available, the information is printed to a window that pops up when you click the SUBMIT button.

The tgz file on my homepage (scroll to the bottom of the page) contains all the files necessary for building the pyjamas project that generates the experiment. You need to have installed pyjamas for the build to work. The structure of the experiment is reflected in the file natural.py, which contains the python code that pyjamas compiles to javascript. Read the README to get started.

Good luck. Questions & comments welcome!