How to make the ceiling of your room seem higher

If you've ever witnessed would-be buyers looking around a house, you'll have noticed their observations about each room are usually limited to: "hmm, it's a good size" or "hmm, it's rather small". Little wonder then that home-improvers are so often fixated on making their rooms appear as spacious as possible. Design lore will tell them that to do so, they should paint their ceilings as light as possible, and in particular make the ceiling lighter than the walls. This contrast between ceilings and walls, so the advice goes, will increase the perceived room height. Does it really?

The answer, until recently, would have remained elusive. Interior design and architecture are strangely disconnected from psychology research. But a new study by Daniel Oberfeld and his team has defied this tradition. Across two experiments they had 32 participants don 3-D glasses and use a sliding scale to judge the ceiling height of dozens of virtual rooms. The rooms were empty and the colours were in shades of grey so that only lightness was varied. In particular, the ceiling, walls and floor were varied to be either low, medium or high in lightness. The depth (6m) and width (4.5m) of the rooms were fixed, whilst the actual ceiling height varied between 2.9 to 3.1m.

Increasing the lightness of the ceiling did increase its perceived height, so that aspect of design lore was supported. However, contrary to the traditional advice, the rooms also appeared higher when the walls were lighter. Moreover, the effect of ceiling lightness and wall lightness was additive. So the contrast effect endorsed by traditional design lore was refuted. Floor lightness made no difference to estimates of ceiling height, so it can't be overall room lightness that's crucial, but only the combination of wall and ceiling lightness.

Oberfeld and his colleagues said that practical guidelines for increasing perceived room height should be modified in light of their findings. "A rule of thumb consistent with our data," they wrote, "would be: 'If you intend to make the room appear higher, paint both the ceiling and the walls in a light colour. You are free to choose the colour of the floor because it has no effect on the perceived height."

From a theoretical perspective the new results are somewhat puzzling. Traditional research in psychophysics has shown that brighter objects usually appear closer. If people judge the height of a room by estimating the distance between their eyes and the ceiling, you'd think a lighter ceiling would appear lower. The present results suggest people must use some other means to judge ceiling height. Another possibility is that people look at the angles in the corner of the room, where the walls meet the ceiling. Perhaps increased lightness alters the angles via a geometric illusion to make the room seem taller. No, that isn't it either: Oberfeld's team said ceiling and wall lightness should have opposite effects on those crucial angles, which is inconsistent with the finding that both led to an increase in perceived height.

So, thanks to this research, we now know how to make our rooms seem higher, but we don't yet know why the technique works!
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Oberfeld, D., Hecht, H., and Gamer, M. (2011). Surface lightness influences perceived room height. The Quarterly Journal of Experimental Psychology, 63 (10), 1999-2011 DOI: 10.1080/17470211003646161

Post written by Christian Jarrett for the BPS Research Digest.