Individual Differences in Gambling Proneness among Rats and Common Marmosets : An Automated Choice Task

Abstract EN

Interest is rising for animal modeling of pathological gambling.

Using the operant probabilistic-delivery task (PDT), gambling proneness can be evaluated in laboratory animals.

Drawing a comparison with rats, this study evaluated the common marmoset (Callithrix jacchus) using a PDT.

By nose- or hand-poking, subjects learnt to prefer a large (LLL, 5-6 pellets) over a small (SS, 1-2 pellets) reward and, subsequently, the probability of occurrence of large-reward delivery was decreased progressively to very low levels (from 100% to 17% and 14%).

As probability decreased, subjects showed a great versus little shift in preference from LLL to SS reinforcer.

Hence, two distinct subpopulations (“non-gambler” versus “gambler”) were differentiated within each species.

A proof of the model validity comes from marmosets’ reaction to reward-delivery omission.

Namely, depending on individual temperament (“gambler” versus “non-gambler”), they showed either persistence (i.e., inadequate pokes towards LLL) or restlessness (i.e., inadequate pokes towards SS), respectively.

In conclusion, the marmoset could be a suitable model for preclinical gambling studies.

Implementation of the PDT to species other than rats may be relevant for determining its external validity/generalizability and improving its face/construct validity.