In drawing conclusions about the relationship between imagery and perception, a notable difference between them is that

it is harder to manipulate mental images than perceptual images.

Explanation:

Mental imagery: In psychology, the term "mental imagery" is also referred as "hearing in the head" or "visualizing", and is determined as a "quasi-perceptual" experiences of an individual that generally occurs in the absence of any appropriate "external stimuli".

Perception: The term "perception" is referred to as a specific way in which different sensory information is being interrupted, organized, and experienced consciously by an individual.

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