Since the classic studies of Pavlov, a wide variety of researchers have investigated the
process of classical conditioning and used it to investigate animal behaviour.
Recently, researchers in animal behaviour have discovered important new benefits
associated with classical conditioning, now being applied as a way of enhancing
well-being . Pavlovian conditioning occurs when an association between two
stimuli, a neutral stimulus and a biologically relevant stimulus, is created by repeated
paired presentations of both stimuli. When the presentation of the neutral stimulus is
followed by a delay, before the biological stimulus is presented, expectation or
anticipatory behaviour is generated. Anticipatory behaviour is known to elicit the
release of dopamine. As play behaviour is also known to result in the release of
dopamine, and correlates with positive welfare state, studies of the relationship
between anticipatory behaviour and play may generate important new insights for
animal welfare.
In this study I assessed if (i) early weaning influenced the development of playful
attacks and pinning behaviour in rats and (ii) the effects of a Pavlovian conditioning
paradigm on the occurrence of play in both early - and normally - weaned rats. Male
pups were assigned to one of the following treatment groups: (1) an early weaned
(EW) group without exposure to conditioning, (2) a normally weaned (NW) group
without exposure to conditioning, (3) an EW group with a conditional stimulus (CS)
paired to an unconditional stimulus (US) to generate anticipatory behaviour (CS-US),
(4) an EW group with CS-US unpaired, (5) an EW group with US only and (6) a NW
group with US only. Animals in each group were observed for one hour each week
from 4 to 7 weeks of life to record the frequency of playful attacks and pinning
behaviour. EW pups that were not exposed to any form of conditioning had a
significant reduction in the frequency of playful attacks relative to the NW pups
without conditioning; pinning frequencies were low, but the effect was not
statistically significant. The difference in frequencies of playful attacks between the
NW group without exposure to conditioning and all the EW groups was statistically
significant, with the NW groups displaying the highest frequencies of playful
behaviour; pinning changes across those same treatment groups were not significant.
Interestingly, the EW group under Pavlovian conditioning had a higher mean
frequency of playful attacks and pinning behaviour relative to the EW control groups
(i.e. EW with CS-US unpaired and EW with US only). Eliciting anticipatory
behaviour may explain the increased levels of play behaviour in the EW conditioned
group. Weight increases were similar across all EW and NW groups.
The results of this study are discussed in relation to the effects that early weaning has
on behavioural development, the potential benefits of using anticipatory behaviour to
reduce the impacts of stressful events, and its positive effects in the development of
play behaviour in rats. The findings support the idea that a Pavlovian conditioning
paradigm can be used to enhance the welfare of animals and that the expectation for
the reward has a greater effect than the reward itself.
