In two. experiments on appetitive learning we conditioned lambs, Ovis
aries, to particular concentrations of a flavour by mixing the flavour
with an energy-rich food that complemented their energy-poor diet. Th
e lambs were subsequently offered energy-rich food with five different
concentrations of the flavour (the concentration to which they were c
onditioned, two higher concentrations, and two lower concentrations).
At these tests, the lambs consistently preferred the weaker flavours.
This finding stands in contrast to earlier results on generalization g
radients. In a third experiment, similarly designed to the other two,
we tested for effects of a strong flavour on the behaviour of lambs wh
en they were offered a novel nutritious food. Half of the lambs were o
ffered unadulterated wheat, and the others strongly flavoured wheat. W
e found that the flavour in itself was initially aversive. We propose
that the lambs' avoidance of foods with strong flavours may be an expr
ession of a rule of thumb of the type 'given a choice, avoid food with
strong flavours'. Such a rule could be part of a risk-averse foraging
strategy displayed by mammalian herbivores, and which could be of par
ticular importance when they encounter unfamiliar foods. (C) 1998 The
Association for the Study of Animal Behaviour.