Final answer:
The perception of the St. Louis Arch's height being greater than its width is likely due to the monocular cue of linear perspective, where parallel lines appear to converge in a two-dimensional space.
Step-by-step explanation:
The perception that the height of the St. Louis Arch is greater than its width is most likely contributed to by the monocular cue of linear perspective. Linear perspective is a visual cue that allows us to perceive depth in a two-dimensional figure, such as a photograph or drawing.
It is based on the phenomenon that parallel lines appear to converge as they recede into the distance, which contributes to the perception of depth and, consequently, affects our interpretation of the dimensions of objects within that space.
An example of this would be how the lines of the Arch itself, along with contextual cues in the environment, might suggest a sense of depth that makes the height of the Arch appear greater. Additionally, other monocular cues such as the relative size of objects in the scene can also play a role in enhancing the perception of the Arch's height compared to its width.