Final answer:
It is often difficult to perceive the grouping of rocks differently once a face is seen due to the influence of perceptual set, which shapes our expectations and interpretations.
Step-by-step explanation:
Once you perceive a particular grouping of rocks as a face, it is often difficult to perceive them in any other way. This phenomenon is due to a principle in psychology known as perceptual set, where expectations influence perception and can make it challenging to see alternate interpretations once an initial one is formed.
An example of this is the pareidolia effect, where people see faces in inanimate objects, such as the 'face on Mars' in satellite images. In the context of sedimentary rocks, the identification process is complex and involves understanding the rock's history, formation, and characteristics like facies and way-up indicators.