Abstract: Reducing false negatives and finding new classes in object detectors is disclosed. Also disclosed is a method that includes grouping together a plurality of cropped image portions from region proposals based on image properties. The method also includes receiving first user input that either establishes that the grouped together, cropped image portions relate to uninteresting objects or establishes that the grouped together, cropped image portions relate to an object class of interesting objects. The method also includes obtaining, only when the grouped together, cropped image portions relate to the object class of interesting objects, second user input that includes an object label corresponding to the object class of interesting objects.