There are no formal responsibilities as such for PSi Graduate Student Committee members.
As co-chairs, Melissa and I have responsibilities to attend PSi conferences and board meetings to feed back views and information regarding our members, but being in the committee is really just about establishing connections between international PS graduates and sharing your thoughts about PS with the group - either online or at committee meetings which take place at the annual PSi conference.
However, we're also currently involved in an outreach initiative to try and attract a more genuinely international membership to the committee and to PSi in general, and we'll be asking all members for some support with that, eg. finding contact info for relevant departments/schools, sending out email invitations on behalf of the committee etc.
NB. Membership of the PSi GSC does not include official membership to PSi. Anyone who attends a PSi conference automatically receives a year-long membership to the organisation.