[LINK] "Fish Learn To Use Tools, So Let's Rethink the Definition of Tool Use"

[rfmcdonald]

io9's Jason Goldman argues that the ability of Atlantic cod to use ersatz tools requires us to really think about definitions of what a tool is and how they are used.

In a recent study, a group of researchers led by Sandie Millot designed a feeding machine that could be operated with a pull string. If a fish was hungry, it would swim up, pull the string, and the food would be dispensed. Since fish – like all other animals – are capable of associative learning through basic classical and operant conditioning, the fact that fish could learn to operate this sort of basic feeder is not surprising. Indeed, 48 of 56 fish figured out how to get the food. Each of the fish was marked with a small tag with a colored bead on it just in front of the dorsal fin. The tags helped the researchers to identify each individual fish.

The surprising part is what happened next. Three of the fish figured out that they could use the artificial tags, rather than their mouths, to operate the feeder. They learned to swim past the string and hook it onto their tags so that the food would be released that way. Since the researchers caught everything on video, they could carefully analyze the surprising behavior.

For each of the fish, the moment of insight began by accident. The fish appeared to accidentally catch their tags on the feeder's pull-string. As soon as they felt the pull of the string, they showed what's called a startle reaction: they immediately responded with a fast burst of swimming until the tag became unhooked. Eventually, after a bit of trial and error and fine-tuning, all three fish were performing the action with apparent intention, using their dorsal tags alone rather than their mouths to operate the feeder.

The argument:

[T]he researchers argue that whether the action qualifies as tool use should hinge on cognition rather than behavior. "The question is not how an animal uses a tool or an extension of the body but why." The why, in this case, is to obtain a desired goal.

"If we accept that the cod were aware of the morphological extension (the tag) on the back," they reason – and how could we not, given how their behavior become more fine-tuned over time? – then "using this to activate a feeder could be regarded as a form of tool use." The researchers even go so far as to suggest that the tag could be thought of as a sort of artificial limb!

The surprisingly sophisticated development in fish of this goal-directed behavior suggests that the usual definition may be insufficient to capture the full range of tool use in all animals. Instead, Millot and colleagues offer a more nuanced characterization of tool use, which relies upon understanding the mental machinery that underlies the innovative behavior, rather than simply describing the innovation itself.