But those who suggest that incest is fairly harmless on the grounds that many children don't object to it do forget that a young child has no concept of sexual norms against which to evaluate her experiences; there is no such thing in her mind as an 'incest taboo' and she may well think that this is a fairly usual aspect of the father-daughter relationship. Later, the child's sense of shame and dissonance is the greater. It is pointless to ask whether the sexual encounter in itself is damaging, or whether it would be damaging on a desert island.
Sloane and Karpinski found, as did Ayalon, that incestious relationships were more emotionally upsetting as the child approached adolescence and the behaviour was seen more and more as socially inappropriate. Whatever we my think of it, children have to conform to society's major norms as they are - otherwise they will become ill, depressed or delinquent. And, as a result, the cycle is likely to continue.
source: Article 'The child' by Morris Fraser (Consultant Psychiatrist, University College Hospital, London); From the book 'Perspectives on Paedophilia' edited by Brian Taylor (Lecturer in Sociology, University of Sussex); Batsford Academic and Educational Ltd; 1981