Check if its the first checkbox is clicked

I have a list of checkboxes like so:

<div class="checkbox-list">
     <label><input type="checkbox" value="" /> All items</label><br />
     <label><input type="checkbox" value="1" /> First item</label><br />
     <label><input type="checkbox" value="2" /> Second item</label><br />
     <label><input type="checkbox" value="3" /> Third item</label><br />
     <label><input type="checkbox" value="4" /> Forth Checkbox</label>
</div>

The behavior I am looking for is if I select the first checkbox in this div (.checkbox-list input[type=checkbox]:first) all other checkboxes after is checked off. Likewise if I select any other than the first, the first one is deselected.

I am struggling on how to check if the first one is clicked on?

$(".checkbox-list").on("change", "input[type=checkbox]", function () {
    if ($(this).first()) { // <- not working - how do I know if I clicked the first one?
        $("input[type=checkbox]:checked", ".checkbox-list").not(this).prop("checked", false);
        $(this).prop("checked", true);
    } else {
         // Uncheck first checkbox
    }
});

Here is a fiddle if you wish to play around: http://ift.tt/1Ggjc3o