This seems like it should be blindingly obvious, but I cannot see the answer. Does NFS have caching? How does it work? Does it simply leverage your operating system/filesystem caching? Does it depend on the client or server you are using?
I'm using NFS as a client on Solaris with no special mount options.
NFS itself does not have caching, however your operating system may do some caching at the filesystem level.
From RFC 1813:
The NFS version 3 protocol does not define a policy for caching on the client or server. In particular, there is no support for strict cache consistency between a client and server, nor between different clients.
http://www.unixcoding.org/NFSCoding explains some of the practical issues with NFS caching.