I was given amazon gift cards as incentives for completing studies on a platform as a participant. Do I report this as self employment earnings?

No.  This would not be considered self-employment income, however it would still be taxable income just not subject to SE Tax.

You will enter this as Other income if you did not receive a 1099-NEC.

  If you did receive a 1099-NEC then you will enter this in the section for the 1099-NEC but as you walk through the steps you will select that this is not income from self-employment. 

To enter your Amazon gift card income without a 1099-NEC select the following:

1. Federal
2. Income and Expenses
3. Scroll down to Less Common Income and click Show More
4. Start next to Miscellaneous Income
5. Start next to Other Reportable Income

This will put it on line 8z of your schedule 1 as other income. 

 (note your navigation may be slightly different due to differences in user experiences)