I have practiced small animal medicine for 35 years. There are a variety of problems that I encountered for which there was no straight forward solution. Behavioral problems such as aggression between cats, periuria without a medical cause, anxiety including separation anxiety, destructive behavior (for example chewing on walls and door jambs), aggression towards people and apparent inability to learn. Of course there are many other issues.
These issues can be traced back to development disturbances which result in lack of foundation and vulnerability. These animals tend to be very reactive, often to normal environmental stimulation. They can’t feel the here and now safety of their circumkstances. Rescue animals (abandoned animals), animals separated from their mothers too early or lose their mothers, animals that have medical procedures during critical developmental periods are some examples. Cell memory is a subject that is getting more attention. A dog or a cat cannot consciously remember an event that has happened during the first 2 to 3 months of age but lives with the memory in its cells. That memory drives behavior.
Certain stimuli from the outside world can “trigger” an animal into a behavior because the stimuli touch a traumatic memory in the cells of the animal, reminding the animal of pain or danger, either physical or psychological. The animal reacts on this, and they often do not know what they are doing. The reaction is essentially a subconscious or unconscious act, not relevant to their here and now circumstances.