Neural Selectivity for Real-World Object Size In Natural Images

Abstract

Real-world size is a functionally important high-level visual property of objects that supports interactions with our physical environment. Critically, real-world-size is robust over changes in visual appearance as projected onto our retinae such that large and small objects are correctly perceived to have different real-world sizes. To better understand the neural basis of this phenomenon, we examined whether the neural coding of real-world size holds for objects embedded in complex natural scene images, as well as whether real-world size effects are present for both inanimate and animate objects, whether low- and mid-level visual features can account for size selectivity, and whether neural size tuning is best described by a linear, logarithmic, or exponential neural coding function. To address these questions, we used a large-scale dataset of fMRI responses to natural images combined with per-voxel regression and contrasts. Importantly, the resultant pattern of size selectivity for objects embedded in natural scenes was aligned with prior results using isolated objects. Extending this finding, we also found that size coding exists for both animate and inanimate objects, that low-level visual features cannot account for neural size preferences, and size tuning functions have different shapes for large versus small preferring voxels. Together, these results indicate that real-world size is an ecologically significant dimension in the larger space of behaviorally-relevant cortical representations that support interactions with the world around us.

What drives the automatic retrieval of real-world object size knowledge?

“…Moreover, animate objects are processed in distinct regions of visual cortex compared to manmade objects, and visual cortex does not show a size organization for animate objects (Konkle & Caramazza, 2013; but see Luo et al 2023); and yet, we find strong size Stroop effects for animate objects in the current study. These considerations suggest that the size Stroop effect does not directly map onto the object size organization of the ventral temporal cortex.…”

“…Moreover, since animate objects may be recognized faster than manmade objects (New et al 2007), the size Stroop effect for animates could even be stronger than that of manmade objects. Finally, animate objects offer an interesting test since they, unlike manmade objects, do not show a real-world size organization in the human ventral stream as measured with functional magnetic resonance imaging (fMRI) (Konkle & Caramazza, 2013; but see Luo et al 2023).…”

What drives the automatic retrieval of real-world object size knowledge?

“…However, unlike real objects, there is currently no evidence linking the size Stroop effect of texforms to the ventral stream. Moreover, animate objects are processed in distinct regions of visual cortex compared to manmade objects, and visual cortex either does not show a size organization for animate objects (Konkle & Caramazza, 2013) or shows a relatively weak size organization for animate objects relative to manmade objects (Luo et al, 2023); and yet, we find stronger size Stroop effects for animate than manmade objects in the current study. These considerations suggest that the size Stroop effect does not directly map onto the object size organization of the ventral temporal cortex.…”

“…Moreover, since animate objects may be recognized faster and more automatically than manmade objects (New et al 2007), the size Stroop effect for animates could even be stronger than that for manmade objects. Finally, animate objects offer an interesting test since they do not (or only weakly, relative to manmade objects) show a real-world size organization in the human ventral temporal cortex as measured with functional magnetic resonance imaging (fMRI; Konkle & Caramazza, 2013;Luo et al, 2023).…”