While it is possible to offer a rough beginning and a rough end, there are simply no absolute boundaries. This is true for rats, humans, and any other species that you could imagine studying. In general, adolescence is considered a transition from childhood to adulthood, a period during which an individual acquires the skills necessary to survive on his/her own. It involves changes at numerous levels, some of which are defined biologically and some of which are defined behaviorally. In humans, some have offered that adolescence encompasses the entire second decade of life (i.e., 10-20 years of age), while others suggest that 12-18 is a more conservative range (Spear, 2000a,b). In rats, adolescence is even trickier to define than in humans. A rough estimate of the age range for adolescence in rats is between 30-50 days of age (Little et al., 1996). .
As you can see, there is simply no fixed age range to define the boundaries of adolescence. In fact, the transition from childhood to adulthood could actually be extended or shortened depending on the individual and the demands placed on the individual by his/her surroundings. It is also important to recognize that, because adolescence is a period of development during which a multitude of changes are taking place, the onset and offset of adolescence is, in the end, determined by how it is operationally defined. Linda Spear (2000a,b) suggests that the following changes are all typical of adolescence and should, along with other factors, be considered in any attempt to define its range: .
1) Increase in time spent with peers, decrease in time spent with family .
2) Increased risk-taking and exploration (could include experimentation with drugs and alcohol).
3) Females show an increased focus on children .
4) Increase in conflicts with family .
5) Typically an increase in eating (though not so in some Western cultures) .
