Sensitivity to reflection and translation is modulated by objectness.

The salience of a transformation between a pair of contours depends on the type of transformation (eg a reflection or a translation) and also on figure-ground organisation. Reflection is most salient when both contours belong to the same surface, and translation is most salient when they do not connect a surface. These findings are based on reaction time (RT). Here I replicate and extend them by measuring both RT and sensitivity. The figure-ground relations were changed unambiguously by using stereograms. I compared reflection and translation when they were present within a surface or across surfaces (experiment 1), and within an object or a hole (experiments 2-4). Holes are interesting because they are not objects, but their presence does not increase the number of total objects in the scene. The within-surface advantage for reflection was present in all experiments. There was a between-surface advantage for translation in experiment 1 but there was no hole advantage for translation in experiments 2-4. Thus the effect of context, ie objectness, on detection of regularity is a robust and general phenomenon present in every experiment, but the type of interaction differs for reflection and translation.