Pavlov's Platypus

One of my colleagues told me about the lake outside the GlaxoSmithKline building in Ware, Hertfordshire. The lake is stocked with Koi Carp and spanned by a wooden bridge. For nine months before the building opened, a man was paid to walk over the bridge every day, feeding the fish as he went. Now, when clients of the company arrive, they are obliged to cross the bridge to reach the building entrance. Schools of fish suddenly appear beneath them and follow their every step across the lake.