The difference between objects and scenes... random thoughts [Of Two Minds]

I'm in the middle of my qualification exams and ran across this interesting paper:

Liu, Z Kersten, D Knill, DC Dissociating stimulus information from internal representation--a case study in object recognition. Vision research. 1999; 39(3): 603-12.

However, I'm very confused about them calling the figure on the left an object. This is a collection of objects in 3D space - making it a scene. I'm not sure that this nullifies their model - but this is not object recognition.

People should really start using ideal observer analysis with scene perception...