Goldfish have strong associative learning abilities, as well as social learning skills. In addition, their visual acuity allows them to distinguish between individual humans. Owners may notice that fish react favorably to them (swimming to the front of the glass, swimming rapidly around the tank, and going to the surface mouthing for food) while hiding when other people approach the tank. Over time, goldfish learn to associate their owners and other humans with food, often “begging” for food whenever their owners approach. Which is an example of classical conditioning, like the experiment that Pavlov did with dogs, where he conditioned the dogs to salivate (conditioned response) to a bell (which was a unconditioned stimulus but become the conditioned stimulus)
And as some of you might know i just brought two fancy goldfish, and already they are getting used to me, (e.g. coming round to my side of the fish bowl, whereas they would swim frantically when others approach).