  Starting with a percolation model in $\Z^d$ in the subcritical regime, we
consider a random walk described as follows: the probability of transition from
$x$ to $y$ is proportional to some function $f$ of the size of the cluster of
$y$. This function is supposed to be increasing, so that the random walk is
attracted by bigger clusters. For $f(t)=e^{\beta t}$ we prove that there is a
phase transition in $\beta$, i.e., the random walk is subdiffusive for large
$\beta$ and is diffusive for small $\beta$.
