Why do cats seem to stare at things that are not there? The short answer is that there is something there and your cat has heard it or seen it but you have not. She is more likely to have heard something or seen movement. A cat’s hearing is acute and their eyesight is attuned to movement. They are very sensitive to movements that we miss and sounds that are too high in frequency for us to hear.
This happens to me quite a lot. My cat will be lying down next to me, content as Larry, and suddenly for no apparent reason he’ll become alert. His ears will point forward and he’ll get up and investigate. My first thought is that something is happening which I have failed to hear so I sometimes follow him. Invariably he is right. It will probably be a bird in the garden, perhaps a pigeon waddling along on the ground or a squirrel making some noise or occasionally a neighbour’s cat has turned up outside the fence.
The other day I was carrying him to the confinement fence at the rear of the garden to be with him there and to see if the foxes were about. I saw and heard nothing but he looked intently into the distance. I followed his gaze but saw nothing. After several seconds a fox appeared. My cat had seen him well before I was aware of the fox’s presence. He had probably picked up a sight movement of the grass and heard something.
Sometimes cats look at the walls of our homes and it looks like they are staring at nothing. You investigate and there it is: a tiny insect crawling up the wall.
Also cats are known for their curiosity. They will respond to slight noises and movements whereas we tend to be relatively disinterested in these minor intrusions.
Their curiosity is fired up by their survival drive. It is about protecting against a hostile intrusion or being alert to prey. Either way the domestic cat will react if he picks something up with his ‘radar’ which he considers of interest and which have not noticed.