Count as "Activity" or "Employment"?

<p>There are three slots for summer activities and three slots for employment on the MIT application.</p>

<p>This summer, I volunteered (technically I was a non-paid employee) at a research lab. Should I list this under activity or employment?</p>

<p>I have never had a job so the employment section is looking pretty empty. Does it matter/help with admissions if you have been employed?</p>