This study used a novel task, clock arithmetic, and a classic A-B/A-Br tran
sfer design to investigate the presence of interference between cognitive s
kills. The A-B/A-Br design required participants to first learn problem-to-
answer associations during training and then to learn new pairings between
the same problems and answers during transfer. The associations teamed duri
ng training interfered with those learned during transfer, as measured by s
lowed reaction times to emit the correct response, failures to retrieve any
response, and intrusion errors. Interference persisted even after a I-week
retention interval and was especially prevalent during the warm-up period
at the beginning of the retention test. The use of the A-B/A-Br design indi
cates that whether an incorrect answer retrieved from memory is emitted as
a response depends on whether the intrusion is recognized as inappropriate
for the current task. The long-term memory for cognitive skills means that
attempts to learn new responses to old stimuli will be plagued by persisten
t intrusion errors.