The nature of perception perceptions: experiences resulting from stimulation of the senses. Object can be hidden or blurred the problem of hidden objects occurs any time one object obscure part of another object. Many understand that the part that"s covered continues to exist, and able to use their knowledge of the environment to determine what is likely to be present. Objects look different from different povs objects are often viewed from different angles. Means, that the images of objects are continually changing, depending on the angle from which they are viewed viewpoint invariance: ability to recognize an object from different viewpoints two types of info used by the human perceptual system. Perceiving objects an example of how top down is involved in perceiving objects. Hearing words in a sentence example of top down influences speech perception. Hermann von helmhotz, made important contributions, invented the ophthalmoscope: allowed us to examine the blood vessels inside the eye.