Dogs are used by the Transportation Security Administration (TSA) at airports nationwide to sniff out explosives and contraband. TSA officials say the agency is increasingly replacing retired pointy-eared dogs like German shepherds with floppy-eared dogs like Labrador retrievers, noting that passengers are generally more accepting of dogs with floppy ears. The TSA cited a 2016 study on ear-cropping and tail docking co-authored by researchers Katie Mills, Jesse Robbins, and Nina von Keyserlingk which found that participants perceived dogs with cropped ears or docked tails as more aggressive and dominant than those with natural features.