Different presentation modalities give rise to modality dependent features that differ in terms of their discriminability. The auditory modality gives rise to cues that can often be more useful in retrieving items than the visual modality. This assumption has been operationalized within the model by using more modality dependent features for auditory items than for visual items. The perturbation process produces a positional uncertainty distribution, a set of values that indicate the probability that a cue was initially encoded as representing each serial position. When recalling a list of items, the cue that, according to its positional uncertainty distribution, has the largest probability of originally being in the first position will be used first.
Similarity is simply a distance measure based on the relative number of mismatching features.
Once an item has been sampled, it must also be recovered. The probability of recovery is related to the number of times the item has already been recalled, and is thus a form of output interference. The first number is the suggested value, and the second part is the range of allowable values. So, the default value is a six item list, but you can specify any list length between 1 and 12. If you enter a value that is not legal or is out of range, the question will be repeated.