An increase in the amount of material to be learned increases the difficulty of the learning task. The function describing this length difficulty relation was obtained by measuring the amount of time 20 college students spent studying arrays of four, six, eight, and ten consonants before they were ready to be tested on them. Identification and location tests were used. For the identification task the length difficulty relation was linear while for the location task a power function with an exponent of 2.39 described the relation. The difference between recognition and recall is qualitative. Students can be expected to assimilate large quantities of information for recognition, while recall requires slower and more careful presentation. Just what is required for a careful presentation remains a problem for future research. (Author)