Jwc. Breukelaar et Jc. Dalrymplealford, TIMING ABILITY AND NUMERICAL COMPETENCE IN RATS, Journal of experimental psychology. Animal behavior processes, 24(1), 1998, pp. 84-97
Counting and timing ability in Wistar rats was tested in 4 psychophysi
cal choice experiments. After training naive rats with discrete sound
sequences that confounded time and number, only time gained control of
behavior; control by time was stronger and acquired more rapidly afte
r training with separate time-and number-relevant signals. Two nonnume
ric cues associated with periodic sequences, temporal ratio and sequen
ce pattern, did not appear to provide the basis for numerical discrimi
nation, as performance was unaffected by a sudden change from periodic
signals to signals with unique temporal patterns. Even after highly a
ccurate performance with number, time showed exclusive control of beha
vior for signals with conflicting time and number cues. This study pro
vides an unequivocal demonstration that rats can count, but they do so
according to H. Davis and J. Memmott's (1983) ''last resort'' hypothe
sis.