  An exact-diagonalization technique on small clusters is used to study the
dynamics of the one-dimensional symmetric Anderson lattice model. Our
calculated excitation spectra reproduce key features expected for an infinite
Kondo lattice such as nearly localized low-energy spin excitations and extended
regions of `heavy-quasiparticle' bands. We show that, in contrast to the
hybridization picture, low-energy spin excitations of the nearly-localized
$f$-electron system play a key role in the formation of an almost
dispersionless low-energy band of heavy quasiparticles.
