You can add public marketing preferences to your survey, allowing respondents to opt into them, whilst existing contacts can opt out.
If it's a survey that's assigned to a contact data field, the marketing preferences will be stored against the contact. If it's a survey that's assigned to a contact data field and your using the 'Consent' element too, the marketing preferences will be stored as ConsentInsight against the contact.
The marketing preferences contacts opt into are included in survey exports.
Configuring a marketing preferences element
Select the Marketing preferences element from the left-hand side panel and drag it in.
This will add a list of preferences based upon the public preferences which are currently set in your account.
To update your marketing preferences list, you'll need to edit the marketing preferences of your account. Click on Manage preferences in the 'Marketing preferences settings' side panel and you'll get taken straight to your marketing preferences page.
If your survey has already been shared, any changes will take effect after around 10 minutes.