When the human eye views a photo, or anything for that matter, it always tries to follow the simplest path of action that it can. Our brains are constantly forming and compartmentalizing spacial relationships between objects, shapes, lines, and (more abstractly) ideas.
Path of Action: When a photo has a smooth compositional path of action to follow, it allows for the eye to continue cycling around that path with minimal fatigue. In the example below, you'll notice that there is a very clear path that pulls the viewers eye back into the composition. As a result, the viewer can look for a longer period of time without eye fatigue. This doesn't mean the viewer WILL look for an extended period of time, but that depends on their interest level in the subject matter itself.
Spacial Relationships: The physical arrangement of multiple subjects within a frame can be a powerful tool in your photography. Relationships give context, which allow the viewer to assess how the two subjects may feel or compare to each other. Their scale and positioning are relevant factors while conveying dominance within the composition.
Directionality: This concept applies directly to posing specifically, and helps sell the viewer on how subjects may feel about each other. In the example below, the two Jellyfish appear as a parent and child due to their positioning and posing. This moment flashed by very quickly, but in the split second that these two (likely unrelated) subjects passed, I felt like that particular freeze frame told a nice story. Their directionality gave them a relationship, and I imagine the scene as a parent leaning down and pointing off screen as its child looks on in admiration. When characters lean in to each other, it tends to be a sign of interest or affection. When characters lean away from each other, it's more likely a sign of fear or disinterest.
Notice the scale, posing and spatial relationship.
It's important to avoid ambiguity, because it removes context and makes for a boring interplay between compositional elements. These concepts play a key role in dictating how the viewer will feel about the subjects within frame.