6.3.2. Aversive conditioning of sting extension
In the second situation, a conditioned stimulus is paired with a shock known to elicit sting extension. The bee is harnessed between two electrodes and after a number of odour-shock pairings the sting extends to the odour (Vergoz et al., 2007; Carcaud et al., 2009; Giurfa et al., 2009; Mota et al., 2011). In contrast to the shuttle box conditioning studies, which involve some type of consequence consistent with operant conditioning (escape, punishment, avoidance), the sting extension procedure is an application of classical conditioning and can be classified as an example of "fear" conditioning. It is important to note that at this time the learning curves associated with the classical conditioning of sting extension are quite low compared to classical conditioning with appetitive stimuli and when appetitive stimuli are combined with shock to an extended proboscis. In contrast to other aversive conditioning protocols, a start has been made investigating the effect of such training variables as number of trials, inter-stimulus interval, and inter-trial interval on sting extension conditioning (Giurfa et al., 2009). Recently, the sting response assay was used to demonstrate that bees learn well to differentiate between different colours under laboratory conditions, which otherwise inhibit visual learning (Mota et al., 2011).