Fly Psychology?

These pages contain my entire body of work concerning learning and memory of the fruit fly Drosophila melanogaster. The paragraph below summarizes the most important aspects of this work. Detailed discussion of the data as well as the necessary background information can be found in the links to the left.

The possible equivalence of learning about the relations in the world (classical conditioning) and learning about the consequences of one's own behaviour (operant conditioning) has attracted much attention throughout the 20th century. By the time I started working on the subject (1995), most psychologists had concluded that learning situations inseparably comprised components of operant and classical conditioning. With the Drosophila flight simulator, a separation could finally be accomplished, however. The paradigm allows one to set up either a contingency between the fly's behaviour and both conditioned (CS) and unconditioned stimuli (US) simultaneously (i.e., a three-term contingency) or any single contingency with the US [i.e., CS-US (classical) or behaviour-US (operant)]. Using two different experimental designs, I could show that a three-term contingency is more effective in producing learning than either classical conditioning alone (i.e., the CS-US association) or operant conditioning alone (i.e. the behaviour-US association, see Diploma thesis). Suspecting that operant and classical processes might act additively to bring about the facilitated learning in the three-term contingency, I set up behaviour and CS as equivalent predictors of reinforcement. If both operant and classical processes worked additively, I expected equal amounts of associative strength accrued by both the behaviour and the CS, when both were tested separately after the training. However, only the CS produced a significant learning score alone while the behaviour did not (see detailed report). This result shows unequivocally that operant and classical processes are not additive, but interact in a more complex way during such 'composite' conditioning (i.e., where CS and US presentations are the consequences of operant behaviour). Apparently, the control of the stimuli by the operant behaviour facilitates acquisition of the classical CS-US association. Considering that most stimuli in natural learning situations are under operant control, this seemingly surprising conclusion makes evolutionary sense.