Though not assured to happen, hiccups can occur if one eats or drinks too quickly. They often occur with sudden temperature changes and intense emotions. While hiccups have been observed to happen in concurrence with these events, it is not known why the diaphragm involuntarily contracts in these situations.
Hiccups result from spasms of the diaphragm and sometimes occur with no obvious cause. These spasms force a rapid intake of air, causing the flap of skin at the top of the windpipe to close quickly. This rapid movement is the source of the noise. Hiccups that do not go away can be a sign of an underlying medical condition.