Next time you're at the airport and a sniffer dog approaches you, note whether it has floppy ears or not... typically the dog's breed will be a beagle, an English springer spaniel, a German shorthaired pointer or a Vizsla, all of which have floppy ears.
According to the US Transportation Security Administration (TSA), floppy eared dogs are preferred in airports since they are perceived as more friendly by the general public. Pointy eared dogs which have a comparable sense of smell - German shepherds for example - are often perceived as less friendly and more aggressive.
The key word here is "perceived" - its a commonly held belief, but is not necessarily correct - the friendliness of a dog depends on the situation and on the individual character of each dog.
Thankyou for reading,
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