Troubleshooting Pack&Go studies

Below is a list of questions Pack&Go users have asked, and their answers. We recommend checking this out before contacting our support team, to see if your question has already been answered. We also recommend looking at our Best Practices for Designing and Implementing Pack&Go Studies to see if any of those recommendations might resolve your issue.

General

My participation links don’t work/the participant encounters an error when trying to access my study

This can happen for a variety of reasons, including:

• The participation link contains a typo or was copy-pasted incorrectly

• The participant’s browser has blocked the website (see below)

• Your study has exceeded the maximum of 20 concurrent study sessions per account

• Pack&Go is currently undergoing maintenance

If you have verified your participation links are correct, please ask your participant to try the link again in an hour or so. In most cases, the error will not persist. If you continue to encounter issues, contact our support team at PacknGo.support@vpixx.com.

I completed a test run but I see no results

Test run results are stored separately from subjects results. They can be found under the “Test Experiment” section of the manage experiment page.

Often, a refresh of the manage experiment page is required. It does not dynamically update when results come in.

My experiment output files are nowhere to be found

Make sure that the output files do not already exist in your experiment zip.

Pack&Go considers anything already present as input, and new files after the experiment execution as outputs.

A participant is blocked from the site due to a firewall

This happens with institutional networks (University, Hospital, School wifi) that have aggressive security measures. The easiest solution is to ask the participant to use a private internet connection instead. If this is not possible, they can ask their IT department to whitelist Pack&Go. The relevant information for the IT team is found below:

Keyboard input works fine locally, but is unstable/does not work on Pack&Go

If you are using a non-Latin alphabet/keyboard (e.g. Arabic, Hebrew, Cyrillic), please contact us at packngo.support@vpixx.com. If you are using a Latin alphabet and keyboard, then this is likely due to a browser extension capturing/altering keyboard input (e.g., imposing keyboard shortcut bindings). The easiest way to correct this is to disable all browser extensions during the session.

I want to screen out participants and end the experiment early/redirect them. How can I do this?

Most recruitment platforms strongly advise against screening participants once an experiment has started. You should use prescreening questionnaires available on these platforms to ensure that only eligible participants are recruited.

Some types of screening (e.g., attention and comprehension checks) can be implemented within a study. Be sure to follow the specific rules for your recruiting platform. You can program your study to end a session that fails these checks early. Pack&Go will still charge credits for the elapsed time, and you will need to manually reject the submission on the recruitment platform.

If your experiment requires very specific screening measures that are not available via the recruitment platform (e.g., certain acuity thresholds, colour blindness), you can create a multi-part study, where the screening task is the first session and those who complete it successfully are invited to participate in the second session. This will ensure you do not waste extra Pack&Go credits running a full experiment for someone who cannot be included in your dataset.

Click on the links below for more information:

• [Prolific] Can I screen participants within my study?

• [Prolific] Valid vs. Invalid reasons for rejecting a submission

• [Prolific] Attention and Comprehension Check Policy

• [Prolific] How do I recruit a custom sample? (Multi-part study instructions)

MATLAB/Psychtoolbox

My experiment starts but nothing happens

1. Check our Best Practices for Designing and Implementing Pack&Go Studies to make sure you have formatted your experiment main file and pathing appropriately

2. Check your experiment.log inside the results zip file. If you did a test run, results will be stored separately and accessible from the manage experiment page. The experiment.log file should contain the same output as when running in local MATLAB. Errors should appear here.

File paths work locally but not on Pack&Go

Pack&Go servers run in a Linux environment, where the case sensitiveness matters. Make sure the file names and paths respect case. Subfolders are permitted but indexing files within those subfolders requires specifying their entire path. Functions like addpath and other changes to the working directory are forbidden.

Experiment does not pack, but runs well locally

Please use MATLAB’s checkcode command to validate your code:

https://www.mathworks.com/help/matlab/ref/checkcode.html
Omit Psychtoolbox Screen SyncTests as these may fail unexpectedly:

• Screen('Preference', 'SyncTestSettings', …)

• Screen('Preference', 'SkipSyncTests', …)

Finally, avoid using any functions in this list:

Python and PsychoPy

Pack failed - Module not found

Most likely, the module that is not found is included in your local version of PsychoPy/Python, but is not included by default on our server. In this case, you can manually add the module by including it in your requirements.txt file (see Uploading your experiment to Pack&Go - Recommendations for preparing your Python and PsychoPy experiment for Pack&Go).

Experiment hanging/keyboard input not registered

Make sure you are using the Keyboard class, and not the older, generic event class in your code:
Bad:

from psychopy import event

# Wait for spacebar press to start
event.waitKeys(keyList=['space'])

Good:

from psychopy.hardware import keyboard   
kb = keyboard.Keyboard()

# Wait for spacebar press to exit
kb.waitKeys(keyList=['space'])

Still have questions? Contact our technical support team at PacknGo.support@vpixx.com