According to Wertheimer's tachistoscope findings, perception is:

Wertheimer's findings with the tachistoscope contributed significantly to the field of Gestalt psychology, emphasizing that perception is an active process that goes beyond the mere collection of individual sensory inputs. This perspective argues that our interpretation of sensory information is shaped by inherent organizational principles, leading us to perceive whole structures rather than just a collection of separate sensations.

The choice that indicates perception is "not merely the sum of sensations" aligns perfectly with Wertheimer's ideas. He highlighted how we tend to group and organize sensory data into coherent wholes, illustrating that our perceptual experiences involve an integrative process influenced by cognitive factors. This means that while individual sensations are crucial, they do not fully define the perceptual experience; instead, the interaction and relationship among those sensations take center stage.

In contrast, the other options present a view of perception that does not align with Gestalt principles. Describing perception as simply the sum of sensations fails to capture the complexities of how we naturally organize information. The notion of perception being a purely passive process overlooks the active role our mind plays in interpreting what we see. Lastly, claiming perception is dependent solely on external factors disregards internal cognitive processes that also shape how we interpret sensory information.