Traditionally, the use of tools was believed to be restricted to humans and several other primate species, and, like language, was argued to be a major driving force behind the evolution of the human brain. However, this view is now being challenged. For example, in recent years it has become clear that birds have sophisticated tool-using abilities. Now, a group of researchers from the RIKEN Brain Science Institute in Japan have demonstrated for the first time that
rats degus* can be trained to use simple tools.
The new study, by Okanoya et al, is published online today in the open access journal PLoS One, and is accompanied by about a dozen short film clips showing the animals using a rake-like tool to varying levels of sophiistication. In this clip, the
rat degu first tries, unsuccessfully, to retrieve pellets of food from behind a screen. With the second attempt, which involves moving the tool forwards, to the side and then back again, it gets the food:
In these trials, the
rats degus payed particular attention to the functional attributes of the tools presented to them, rather than their shape, size or colour. Thus, they chose correctly between a familiar but useless tool and an unfamiliar but functional one. This suggests that they not only formed mental representations of the tools, but also manipulated these representations.
Such behaviour is likely to lead to modifications of neuronal connectivity in various regions of the brain. In a process called synaptic plasticity, the connections between the nerve cells involved can be strengthened or weakened in an experience-dependent manner. It is widely believed that the persistence of these changes over time underlies both learning and long-term memory. Other recent studies further suggest that newly-generated neurons are involved in certain types of learning behaviour.
Most studies of tool-use have been performed using birds or macaques, neither of which are amenable to investigations of synaptic plasticity or neurogenesis. The rodent model of tool-use developed here should now enable researchers to investigate the cellular and molecular mechanisms underlying this complex behaviour. Further, the findings support earlier work which shows that complex cognition is not restricted to organisms which possess what we usually call “higher intelligence”.
Okanoya K, Tokimoto N, Kumazawa N, Hihara S, Iriki A (2008) Tool-Use Training in a Species of Rodent: The Emergence of an Optimal Motor Strategy and Functional Understanding. PLoS ONE 3(3): e1860. doi:10.1371/journal.pone.0001860. [Full text]