- (A) Erroneous perceptions is a correct description of illusions. An illusion occurs when the perception of an object or phenomenon differs from its actual reality, creating an erroneous or distorted perception.
- (B) Schemas refer to mental structures that organize and interpret information based on prior knowledge, but they are not illusions. They help in processing and categorizing experiences.
- (C) Perceptual constancies are the tendency of our perception to remain stable even when the sensory input changes, and they do not represent illusions. In fact, perceptual constancies help us maintain a consistent perception of the world.
- (D) Incorrect perceptual hypothesis aligns with the definition of illusions. It refers to a mistaken judgment or hypothesis about a perceptual experience, which results in an illusion.
Thus, the correct answer is:
\[
\boxed{A), D)}
\]