When a short, low-volume ultra-sonic
sound occurs, an extremely powerful
response occurs. It's called the orienting
reflex.
BTW, has anybody used one of those ultra-sonic whistles? My dogs have
never paid them the slightest attention. Around here (somewhere) is a
tiny box containing one of those from England with a minute piece of
paper outlining a complete training program based on it.




















Just because humans are slow and can't smell or hear
very well doesn't mean they don't possess a primitive
type of intelligence.