The attraction between the particles in a liquid keeps the volume of the liquid constant. The movement of the particles causes the liquid to be variable in shape. Liquids will flow and fill the lowest portion of a container, taking on the shape of the container but not changing in volume.
Liquids flow because the intermolecular forces between molecules are weak enough to allow the molecules to move around relative to one another. In liquids, the intermolecular forces can shift between molecules and allow them to move past one another and flow.
Phychologists helps to answer questions about human and animal behavior. They identify behavior and emotion. Their work is important because they helps us understand our emotions and feelings.