Upon enabling this setting, new survey record submissions will include the Human Confidence Score field.
Values closer to 0 indicate low confidence of human activity, while values closer to 1 indicate high confidence of human activity. Negative scores indicate configuration issues with the Site/Secret Keys.
Surveys with a low Human Confidence Score can be further reviewed for accuracy, and easily filtered out of your reports.
In addition to the Simple Survey setup above, you will need to add https://www.google.com as a Remote Site in your Remote Site Settings. Please see the following Salesforce documentation: