Experimental lifetimes and branching ratios for the alpha-decay of even-eve
n actinide nuclei can be fitted with wavefunctions at the nuclear surface w
hich are practically nucleus independent. This suggests some common preform
ation process across the entire mass region. Our analysis is achieved witho
ut the introduction of a 'knocking frequency' and within reasonably well de
fined limits, the amplitudes that we calculate can be directly related to t
he alpha-particle preformation factor.