Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for adjusting confidence scores of image labels for images. In one aspect, a method includes accessing images stored in an image data store, the images being associated with respective sets of labels, the labels describing content depicted in the image and having a respective confidence score that is a measure of confidence that the label accurately describes the content depicted in the image; selecting a first image from the images and determining for each of the other images and independent of the labels, a proximity score that is a measure of a relatedness of the other image to the first image; and adjusting the set of labels associated with the first image based on the respective proximity scores of the other images and the confidence scores of the labels of the other images.