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Technical Checklist

  • Overview
  • Stimuli
  • File Types
  • File Sizes
  • Devices and Browsers
  • Devices
  • Browsers
  • Connection Speeds
  • Mobile Apps

Overview


This page draws together in one place the technical information you should be aware of before starting to run your study on Gorilla. It covers supported file types, guidance on maximum file sizes, and ways to ensure your participants are able to complete the experiment, whatever device or browser they are using. This information should help you to avoid many known issues when running your experiment.

By far the best way to avoid these issues is to preview and thoroughly test your experiment before recruiting participants. Preview the experiment across different devices and browsers; preview all conditions of your experiment, and download and check the data from each preview to make sure everything is recording as you intended. Recruit a few friends to do the experiment as 'real' participants to spot any issues that might only appear once the experiment goes live.

We do the best we can to make sure all important information is accessible on our support pages, but there is no substitute for thorough testing of your specific study!

File Types


When uploading your spreadsheet(s) and stimuli, using the file types listed below will help to ensure your experiment runs smoothly.

For spreadsheets, Gorilla supports the following file types:

.csv, .xlsx, .ods

For stimuli, we strongly recommend using the file types that are most widely supported by all browsers. These are:

Images: .png, .jpg,, .jpeg, .gif

(Note: we do not recommend the use of non-repeating GIFs. For more information, see our Image Zone guide.)

Audio: .mp3, .ogg

Video: .mp4

(Note: older .mp4 files with out-of-date encoding can cause issues. Handbrake is an open-source tool that can be used to convert older video files to a modern, widely supported format.)

If your audio and video files are currently in a different format (e.g., .wav or .mov), we strongly recommend you convert them to one of the recommended formats listed above before uploading them to Gorilla. For audio, Audacity is an open-source tool that you can use to convert files to .mp3. For video, Handbrake or VLC Player are open-source tools that you can use to convert files to .mp4.

File Sizes


We recommend that the size of spreadsheet and stimuli files be kept as small as possible to ensure smooth running of experiments and minimise pre-loading delays. Specific guidelines will vary depending on how many stimuli you have in your task, but in general, we advise the following:

  • No individual file should be larger than 10MB
  • Each image file should be no larger than 50KB
  • Audio and video files should be less than 2MB per minute

If you have very few stimuli in your task, it may be less of a problem to have one or two files that are larger than these constraints. Conversely, if you have very many stimuli in your task, you may need to reduce the size of each individual file further.

To reduce the size of image files, you can use Squoosh or your preferred image editing software. For audio, Audacity is an open-source tool that includes the option to compress files. For video, Handbrake or VLC Player also offer this option.

Devices


By default, participants will be able to access your experiment from any internet-enabled device (including desktops, laptops, tablets and mobile phones).

We recommend you thoroughly preview and test your experiment on any device you are planning to let participants use. If you know your experiment does not work well on a particular device type, you can prevent participants from accessing the experiment on this type of device by setting Requirements on the Recruitment tab of your experiment.

Note that device type checks are not infallible - in particular, modern Apple devices such as iPhones and iPads are able to identify themselves as computers. As such, if you need to exclude participants who are using a particular device type, we highly recommend that you also directly ask participants within the experiment what device they are using, and use a Branch Node to reject participants or send them on to your task on the basis of their answer.

If a participant using a mobile clicks your experiment link from within a mobile app (such as Facebook or Twitter), the experiment may open within the app, rather than in a full browser such as Safari or Chrome. This may prevent them from completing the experiment. If you are recruiting participants who will be using mobiles, we strongly recommend that you instruct them to copy and paste the link into their browser, rather than clicking it.

Browsers


By default, participants will be able to access your experiment from any browser.

For most simple experiments, the browser will not make a significant difference to participants' experience. However, if your experiment is more complex or you are using cutting-edge features, you may want to preview and test your experiment across multiple browsers. If you find that your experiment does not work well on a particular browser, you can prevent participants from accessing the experiment in this browser by setting Requirements on the Recruitment tab of your experiment.

If a participant using a mobile clicks your experiment link from within a mobile app (such as Facebook or Twitter), the experiment may open within the app, rather than in a full browser such as Safari or Chrome. This may prevent them from completing the experiment. If you are recruiting participants who will be using mobiles, we strongly recommend that you instruct them to copy and paste the link into their browser, rather than clicking it.

Connection Speeds


Participants in your experiment may have varying connection speeds. Gorilla's lookahead system, which downloads all stimuli for a trial before the trial starts, is designed to account for this: a participant's connection speed will not affect the accuracy of their measured reaction time.

However, if a participant's connection speed is slow and the experiment includes a lot of stimuli, very large stimuli files, or a combination of both, they may experience pauses between trials while these stimuli are loaded. The best way to solve this problem is to reduce the size of stimuli files to make them as small as possible - see the File Sizes section for more information.

You also have the option of preventing participants whose connection speed is below a certain level from accessing your experiment. You can do this by setting Requirements on the Recruitment tab of your experiment.

Mobile Apps


If a participant using a mobile clicks your experiment link from within a mobile app (such as Facebook or Twitter), the experiment may open within the app, rather than in a full browser such as Safari or Chrome. This may prevent them from completing the experiment. If you are recruiting participants who will be using mobiles, we strongly recommend that you instruct them to copy and paste the link into their browser, rather than clicking it.