Behavioural data
Autoshaping. The central phenomenon that the model is
meant to account for is the existence of individual behavioural
differences in the acquisition of conditioned approach responses in
rats undergoing an autoshaping procedure; that is, the development
of a sign-tracking CR, a goal-tracking CR, or an
intermediate response.
Based on their engagement towards the lever, Flagel et al. [21]
divided rats into three groups (see [26] for a more recently defined
criterion). At lever appearance, rats that significantly increased
their engagement towards it (top 30%) were classified as STs,
whereas rats that almost never engaged with the lever (bottom
30%) were classified as GTs (these latter animals engaged the food
magazine upon CS presentation). The remaining rats, engaging in
both lever and magazine approach behaviours were defined as the
Intermediate Group (IGs) (see Figure 5 A, B). STs and GTs
acquired their respective CRs at a similar rate over days of training
[22].