After years of having a dog, you know him. You know the meaning of his snuffs and grunts and barks. Every twitch of the ears is a question or statement, every wag of the tail is an exclamation.
All psychedelic explorers should be aware of the concept of what is called a cognitive hallucination. The is a much more insidious phenomenon. This is, quite simply, an out-and-out delusion.