Question:
I think that it was on Tuesday last (Aug 8) that Ruth
remarked, [......] that fish are reputed to have a memory span of 3 seconds.
Does any umrat know whence comes this suggestion? Is it
reliable? How was the determination made?
Back in the 50s it was said that the octopus is quite bright
and can distinguish several different colours.
I understand that this deduction followed from experiments done by presenting the animal with several patches each in a different
colour. In each experiment one of the patches was laid over some food,
and the experimenters were able to show that the octopus rapidly
sussed out that it was always the same colour patch which hid the food
... until some sneaky bod in a white coat changed it to see how long
it took our eight-legged friend to twig and try another colour.
The trouble with this is that although there is no need for an
animal with colour sense to be intelligent this sort of experiment
won't work with a dim creature, since its inability to locate the food
may merely be a function of its lack of intelligence rather than its
poor colour discrimination. So .... do fish have short memories, or are they just dim?
My old animal learning textbook (Mackintosh, 1974) reports the
training of goldfish to push a paddle or swim down an alleyway.
So they are obviously able to learn and retain some things
in long-term memory over significant periods of time (which seem
to be proportional to size of reward).
Then there's short term memory, which is going to be of short
duration, whether you're a goldfish or a person. People can finesse
it by mental rehearsal - eg repeating a new telephone number to oneself
until it's learned or no longer needed. I'm now trying to imagine a
goldfish with a thought bubble, continually rehearsing some similar
piece of information, but am having difficulties ...
...... Well our fish know that it is morning and feeding time, so I am not convinced about either three or six seconds.
They are very old for fish of course.
Given that it's possible to train goldfish to come to the surface prior to feeding by whistling etc. they must have some sort of memory or does all that psychology stuff about salivating dogs override their lack of memory?
If they had such short memories, Shirley goldfish wouldn't "remember" that the site of the owner looming up alongside the tank is a signal that food will shortly turn up?
Yes, you're right. Ours are very strongly conditioned now (since they
reproduced prolifically and the tiny pond is now overstocked) and as soon as they hear or see us, they come to the surface splashing and snarling and threatening to jump out and attack us until we throw some pellets in.
IANA fish, but.....
There are many examples of fish behaviour that suggest the existence of
various different types of memory. The ability of salmon to return to
the river in which they were hatched, after migrating to the sea, for
instance. The mechanism for this is probably different from our concepts
of human memory, but it's memory all the same.
To bring the conversation back to my favourite subject of all time, that
of scaring fish.....
The basic process involves broadcasting electronically-generated noises
under water, which encourage fish to stay away from areas they shouldn't
be in. Our sound-producing equipment has to vary the noise it produces
frequently, or fish become acclimatised to it, and it loses its
deterrent effect. This too suggests a form of memory.
One might ask a different question, in fact - why does a goldfish,
unlike other fish, have a bad memory? Perhaps there's a persuasive
argument that, as their existence is mainly limited to living in
goldfish bowls and other fish tanks, they don't really need one any
more.....
But our home goldfish (of which there were about a dozen over a period of years) would rattle the gravel to attract our attention. And if anyone passed the tank and the fish were hungry, they would swim to the surface and open their little gobs in a way that enticed one to feed them. If this doesn't imply memory it must be a reflex action, so all goldfish would be expected to do the same.
Nope, that suggests memory to me; at least some kind of learned response to a stimulus, as in Pavlov's dogs. Strikes me that the suggestion of a goldfish's short memory needs clarification as to what sort of memory it refers to.
I have recounted this before, but it is relevant again so here goes. The tropical fish in a large tank in the Fairfield Hotel, Nairobi would go into a feeding frenzy when their minder came through the door on the opposite side of the lounge. He did this at about the same time each day and they were waiting for him, watching. But when he went on holiday and I fish-sat, they watched, but they never recognised me.
I wonder, if you'd carried out the feeding routine for a sufficient
length of time, and they had then come to recognise you as the source of
food, whether they would then have recognised the original minder. In
other words, would the second conditioned response have erased the
first, or simply replaced it for a while?
I've no direct experience of goldfish thought processes, and pray God I
never will, but ISTM that their memory functions well as a mechanism for
survival against predation and obtaining food: they can remember that an
organism of a particular size, shape and colouring, moving in a
particular direction, at a time of day when the light is coming from a
certain direction, will be bringing food. What they can't do is to
remember where they were 10 minutes ago - but then neither can I, most
days. It's possible that they've never *needed* to remember that sort of
information - it's not essential to their survival.
Last updated
February 16th 2004
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