Attention is the mental process of bringing few stimuli into the centre of awareness out of the many stimuli present. It is difficult to attend to a single stimulus for a long period of time. Our attention shifts from the original stimulus to another stimulus for a fraction of time and then comes back to the original stimulus. This may be due to factors like fatigue, decreased interest, etc. In most cases, attention fluctuates due to the limitations of human attention and hence cannot be totally eliminated.