They are very small in size and so is their voice, to convey their happiness or displeasure over something unlike other pets; Hamster can not express itself using the vocal means, so it is left with only one thing that is their body language though Hamsters can convey their distress by biting as well.
Having said that; Hamsters convey their feeling through body language but for a moment we have to imagine how many feelings are there; so how can they be translated through body language Hamsters are very good at it. They have different convulsive moments and every Convulsive movement, as well as sudden continual face washing, signifies fright. Defensive raising of both front paws can be observed in males that have been unexpectedly attacked by females and have no way of escaping.
Puffing up the cheeks and showing the abdominal regions are to be construed as a threat. Lying motionless on the back shows resistance and fear. The stiff-legged walking of a young animal, with its tail, stiffly stretched up and its hindquarters turned toward the adult hamster, denotes fear and submission. This can also often be observed in vanquished adult hamsters. Stretching and yawning with half-closed eyes is an expression of cosines and inner peace.