[Corfield]

Page 8

para 1,2 Rest of the article is great reading too

"It is generally agreed that extremes of re-homing, too early (before 6 weeks) or too late
(after 12 weeks), predispose puppies to develop adjustment problems later in life
(Lindsay, 2000). In particular, problems relating to fear and aggression are often
associated with late re-homing. O’Sullivan et al. (2008) found that over 60% of dogs
that had been reported for biting a person were acquired at 12 weeks of age or over.
McGreevy and Masters (2008) also report that the probability of displaying feed-related
aggression (which is also based in fear - Jones-Baade and McBride, 2000) increases
alongside the dog’s age at acquisition"

Lots of properly referenced sources listed at tend of the piece.

"Many sources recommend re-homing between 6 and 8 weeks, right in the middle of
the socialisation period (Fox, 1972; McCune et al. 1995; Lindsay 2000; Bailey, 2008)
with some highlighting 7 weeks (Campbell, 1974) and others recommending 6 weeks
(Freedman, 1991 as cited in Appleby 1997) as the optimal re-homing age. This allows
sufficient time for socialisation with conspecifics whilst enabling the puppy to readjust
to its new environment and socialise with the new owners before the fear imprint
period at 8-10 weeks (McCune et al. 1995). There are some sources that suggest that
6-8 weeks is too early for rehoming (Overall, 1997; Bailey 1994). Dr. Bailey (1994)
argues that reputable breeding environments provide sufficient human contact for
socialisation and waiting until the dog is older (ideally 10 weeks) provides a better
insight into the individual puppy’s physical and psychological attributes. In general, the
optimal time for re-homing a puppy is highly dependent on the provision of socioenvironmental
stimuli within the breeding environment and how this compares to the
ongoing experiences and training that will be provided by the new owners"