To prevent spam being sent via this form, Google provides us with a so-called "reCaptcha" feature. As soon as you click in one of the provided form fields, the reCaptcha logo of Google appears in the lower right corner. In the background runs an analysis during this interaction, which, according to Google, among other things, based on mouse movements conclusions to the question of whether you are actually a human. And not a script that wants to send spam.