Size adaptation effects are independent of spatial frequency aftereffects

Repulsive adaptation effects for spatial frequency, motion and orientation (the tilt aftereffect) are well established, and support the notion of population coding in each of these domains. We have recently proposed (Meese and Baker, 2011 Journal of Vision 11(1) 23, 1–23) that the spatial extent of an object or texture is represented in a similar way. If so, adaptation effects should exist that are sensitive to object size (eg diameter) rather than the scale of a texture (spatial frequency). Using a matching task, we measured perceived size of 4 cycles deg–1gratings before and after exposure to an adaptor that jittered in space to cover the area of the largest target. All eight of our naïve observers experienced a clear shift in perceived size—large targets looked larger and small targets looked smaller. The effect is similar in magnitude (10–20%) to spatial frequency repulsion effects (which we also replicate) but does not induce them: increasing perceived area does not increase perceived bar width. Size adaptation is robust to the relative orientation of adaptor and target, and even occurs for disparate objects such as gratings and faces. This implies adaptation of a broadly-tuned process which estimates the envelope of a stimulus.