CS-dependent response probability in an auditory masked-detection task: Considerations based on models of Pavlovian conditioning Christine R. Mason, Fabio Idrobo, Susan J. Early, Ayome Abibi, Ling Zheng, J. Michael Harrison, and Laurel H. Carney Boston University, Boston, MA, USA Experimental studies were performed using a Pavlovian-conditioned eyeblink response to mea- sure detection of a variable-sound-level tone (T) in a fixed-sound-level masking noise (N) in rab- bits. Results showed an increase in the asymptotic probability of conditioned responses (CRs) to the reinforced TN trials and a decrease in the asymptotic rate of eyeblink responses to the non- reinforced N presentations as a function of the sound level of the T. These observations are con- sistent with expected behaviour in an auditory masked detection task, but they are not consistent with predictions from a traditional application of the Rescorla–Wagner or Pearce models of asso- ciative learning. To implement these models, one typically considers only the actual stimuli and reinforcement on each trial. We found that by considering perceptual interactions and concepts from signal detection theory, these models could predict the CS dependence on the sound level of the T. In these alternative implementations, the animal’s response probabilities were used as a guide in making assumptions about the “effective stimuli”. In recent psychophysical studies (Early et al., 2001; Zheng et al., 2001), we used a Pavlovian- conditioned eyeblink in rabbit to study detection of a tone (T) that was presented in compound with a noise masker (N). These experiments used a feature positive procedure, where TN pre- sentations were always accompanied by the unconditioned stimulus (US), and the noise alone, N, was presented frequently and never with the US. These presentation types are designated TN + and N – , respectively. This training resulted in substantial responding to the TN com- pound and little responding to N. To measure sensitivity for detecting T in the presence of N, Requests for reprints should be sent to Laurel H. Carney, Institute for Sensory Research, Syracuse University, 621 Skytop Road, Syracuse, NY, 13244, USA. Email: laurel_carney@isr.syr.edu This work was supported by National Institutes of Health Grant #DC 01641. The authors wish to thank Dr. Robert Rescorla for his helpful comments on an earlier draft of this manuscript and Dr. John Pearce for his assistance with the implementation of his model.  2003 The Experimental Psychology Society http://www.tandf.co.uk/journals/pp/02724995.html DOI:10.1080/02724990244000052 THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 2003, 56B (2), 193–205 Q2272—QJEP(B)01b28/Mar 31, 03 (Mon)/ [13 pages – 0 Tables – 2 Figures – 4 Footnotes – 1 Appendices]. . Centre single caption. shortcut keys. Edited from DISK