With the release of Mac OS X 10.16 (Big Sur), Apple introduced compatibility-breaking changes to their runtime platform that had the unfortunate effect of breaking the Inquisit Lab 5 editor, causing text to be improperly rendered and making the editor unusable.
Importantly, these changes do not effect the Inquisit 5 Lab and Web runtime, which is responsible for running experiments. Thus, you can still run Inquisit 5 experiments on the latest versions of Mac OS X.
Mac users who wish to create and edit scripts for Inquisit 5 have the following options:
1 - Upgrade to Inquisit 6.
2 - Use Macs with older versions of OS X for script development. The editor continues to work on OS X 10.15 (Catalina) and earlier.
3 - Use Windows computers for script development.
For options 2 & 3, you can freely transfer your Inquisit Lab license to older Macs or Windows computers for the purpose of editing your scripts.