BoundedRationality_TheAdaptiveToolbox.pdf

242 Kevin N. Laland
example, bats that are unsuccessful in locating food alone follow previously
successful bats to feeding sites (Wilkinson 1992). Starlings can use the foraging
success of other birds to assess patch quality, and exploit this information in their
judgements as to whether to stay or switch patches (Templeton and Giraldeau
1996). For redwing blackbirds, the social learning of a food preference is a£
fected by whether the demonstrator bird becomes sick or remains well (Mason
1988). At this stage it is not clear which, if any, of these heuristics provides the
best description of the rules that animals employ when they learn from others.
INNOVATION AND DIFFUSION
When a novel behavior pattern spreads through an animal population, typically
one individual will be its inventor or discoverer. There have been precious few
empirical investigations of who these innovators are. However, evidence is beginning
to emerge that innovators are sometimes individuals for whom the current
prevailing risk-averse foraging strategies are unproductive, and who are
driven to search for alternatives, perhaps incurring some risk. Such animals are
often small, young, low-ranking, or poor competitors. Primate studies appear to
indicate that innovators are frequently low in rank or poor competitors on the
outskirts of the social group (Kummer and Goodall 1985). For instance, Sigg
(1980) found that peripheral female hamadryas baboons were significantly
better at learning novel tasks than central females. A recent review found that of
38 independent cases of innovation reported in the primate literature, 25 were by
low-ranking individuals (S.M. Reader, pers. comm.).
Kummer and Goodall (1985) found no shortage of innovation in primate
populations, but these innovative behaviors rarely spread, in spite of their apparent
utility. It seems that often individuals do not adopt a better alternative, even
when other members of the population exhibit such behavior. This is perhaps because
on many occasions when ecological and technical innovations occur, the
innovator is alone, or at least freed from social distractions (Kummer and
Goodall 1985). If the twin observations, that it is poorer competitors that inna
vate, and that poorer competitors find themselves on the outskirts of aggregations,
are common to many species, much innovation will tend to occur
unobserved by others, decreasing the chance that the novel behavior pattern will
spread. This may be one explanation for both the slow diffusion of new behaviors
in the wild (Kummer and Goodall 1985), and the rarity of stable animal traditions
(Boyd and Richerson 1988).
Empirical research has established a number of factors that influence the stability
of animal traditions, including the number of individuals in a social group,
the rate of change of group composition, and the amount of time available to forage
(Galef and Allen 1995). Social transmission may be more stable when it reinforces
a prior preference (i.e., for a more palatable diet) than when it conflicts
with one (Laland and Plotkin 1991). Whether such pre-established biases reflect