In theses studies, people are shown sequences of letters. These sequences are created using an algorithm. For example, the sequence VXVPS, TPPTS, and VXXXS are valid or "grammatical" sequences, whereas the sequences XVSPV, PPTTS, and SXXXV are not. During a learning phase, people are shown a series of letter strings that were generated using the algorithm and are asked to simply copy the sequence. It has been found that even in the absence of explicit memorization, people learn not just the sequences that were presented but the "grammar" or production algorithm used to generate them. This implicit memory shows itself in people's ability to also accept (at above chance rates) valid sequences that were never seen before and to accept new sequences that used different letter sets but that followed the same rules.