When trying to analyze an animal’s body language, each signal must be taken in context. Other body language signals should be analyzed as well to form as complete as possible view of the animal’s intent or emotional state. You can generally characterize signs in 3 categories: go, stop and yield.
The ears are one of the most expressive parts of the cat’s body. As the ears go back from the vertical position, the cat generally is exhibiting more neurochemical arousal or fear depending on how flat the ears are and what the other parts of the cat’s body language are indicating.
Ears out to the side is usually one of the first signals that the cat is getting aroused or agitated. That is why ears to the side is generally interpreted as a yield sign. It is time to assess what the cat is thinking and interact with him accordingly. When you see a cat give you this sign, it is a good idea to leave him alone as he most likely needs his space!