Stage	Description	Additional notes	References
Simple Discrimination (SD)
Compound Discrimination (CD)	Stimuli vary in two perceptual dimensions, such as color and shape for visual stimuli in the human task, or between texture and odor stimuli for rodents
Reversal learning (CDRe – IDSRe – IDS2Re – EDSRe)	Two exemplars within a perceptual dimension have their reinforcement contingencies reversed so that what was previously correct is then incorrect and vice versa)	In serial reversal learning, performance improves with consecutive within-set reversals. Thus, reversal stages (i.e., CDRe, IDSRe, IDS2Re) not only assess function of different cortical areas, but also serve 1) to form the cognitive- attentional set challenged by the EDS stage, and 2) to prevent superstitious conditioning to unintended aspects of the stimulus	- Lesions of the orbitofrontal cortex in mice (Bissonette et al., 2008) and monkyes (Dias et al., 1996) impaired Reversal learning - fMRI during performance on the Reversal learning showed activation of the orbitofrontal cortex (Hampshire and Owen, 2006)
Intradimensional shift (IDS – IDS2)	Novel exemplars are introduced, but the same dimension is reinforced	IDS stages serve as a crucial internal control (i.e., EDS should be more difficult than IDS), and also contribute to form the cognitive-attentional set	Dopamine depletion in the PFC impaired attentional set formation (Robbins and Roberts, 2007). 6-OHDA lesioned monkeys did not show the classical reduction the reduction in errors from the first (IDS1) to the last (IDS5) discrimination, which should  reflect acquisition of an attentional set
Extradimensional shift (EDS)	‘stuck-in-set’ protocol: previously irrelevant stimulus dimension is replaced by a new stimulus dimension which immediately becomes relevant	failure to shift to the new relevant dimension cannot be attributed to any prior learning about this dimension since it had not been previously experienced. Failure, therefore, reflects perseveration to the previously relevant dimension	- Lesions of the mPFC have been show to impair EDS in mice (Bissonette et al., 2008), and mokeys (Dias et al., 1996) - Frontal lobe patients are impaired in the stuck-in-set 'perseveration' condition but not in the ‘two dimension' condition (Owen et al., 1993) - Dopamine in the mPFC modulated EDS performance in mice (Papaleo et al., 2008; Scheggia et al., 2014) and rats (Tunbridge et al., 2004)
‘two dimensions’ protocol: the previously irrelevant dimension is reinforced	an apparent failure to shift attentional set may arise when a subject is able to shift attention away from a previously relevant dimension (when it becomes irrelevant) but is, nevertheless, unable to refocus attention on the newly relevant dimension	- Lesion of the mPFC in rats (Birrell and Brown, 2000) impaired EDS shift - fMRI during performance on the EDS has been shown activation of the ventro-lateral PFC (Hampshire and Owen, 2006)