Poster orientation: Landscape or portrait (horizontal or vertical)? Which is a better poster orientation: Vertical/portrait (taller than wide) or horizontal/landscape (wider than tall)?  Assume that the content does not "naturally" fit either of these formats so as to make one choice obvious. 

Are there any studies that explore the differences between these two?
If you aren't aware of any, what psychological mechanisms might underly differences in the way people perceive the research (or researcher) based on the difference between the orientations?  

I'm not interested in answers that say "it's just a subjective personal style choice" but am interested in answers that detail at least some difference in what may be perceived or communicated differently as a result of a change in orientation. 

If there are strong field-specific conventions, those would be good to know (because being the only person who fails to follow that structure might give an impression that this person is an outsider or doesn't understand the community) but it'd be nice to have at least some answers that can apply in a very broad multidisciplinary poster session which is too topically diverse for any field-specific orientation convention to apply. 

For the purposes of answering here, please assume the two dimensions are fixed at a bit under 3 and 4 feet, but orientation is not fixed.  



Related: 


What are some general good principles for creating a poster for a poster session?  
Default poster size
While I am not aware of field-specific differences, my personal experience leads me to believe that landscape is likely to be better for conveying information than portrait.  The reasons for this are:


People are much more visually sensitive to vertical than horizontal changes in position, due to the fact that we are largely surface-dwellers.  You'll have a much bigger visual impact from things that are near eye-level than things that are significantly displaced up or down.
Posters are typically consumed in parallel, with different people arriving at different times and looking at different parts.  A landscape format lets more people be close to the poster (and potentially the parts they're focusing on) than portrait format.


That said, 1) many venues restrict you tightly in the amount of space that you are allotted, and it will generally be better to use the space you've got rather than make a smaller poster with a preferred orientation, and 2) good vs. bad graphical design will vastly outweigh portrait vs. landscape in terms of impact.