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.
[32]
Goldfish that have constant visual contact with humans also
stop considering them to be a threat. After being kept in a tank for several weeks, sometimes months, it becomes possible to feed a goldfish by hand without it shying away.
Goldfish have a
memory-span of at least three months and can distinguish between different shapes, colors, and sounds.
[33][34] By using
positive reinforcement, goldfish can be trained to recognize and to react to light signals of different colors
[35] or to perform tricks.
[36] Fish respond to certain colors most evidently in relation to feeding.
[32] Fish learn to anticipate feedings provided they occur at around the same time every day.