Behavioural Processes 69 (2005) 189–205 How rats combine temporal cues Paulo Guilhardi ∗ , Richard Keen, Mika L.M. MacInnis, Russell M. Church Department of Psychology, Box 1853, Brown University, Providence, RI 02912, USA Abstract The procedures for classical and operant conditioning, and for many timing procedures, involve the delivery of reinforcers that may be related to the time of previous reinforcers and responses, and to the time of onsets and terminations of stimuli. The behavior resulting from such procedures can be described as bouts of responding that occur in some pattern at some rate. A packet theory of timing and conditioning is described that accounts for such behavior under a wide range of procedures. Applications include the food searching by rats in Skinner boxes under conditions of fixed and random reinforcement, brief and sustained stimuli, and several response-food contingencies. The approach is used to describe how multiple cues from reinforcers and stimuli combine to determine the rate and pattern of response bouts. © 2005 Elsevier B.V. All rights reserved. Keywords: Packet theory; Temporal cues; Time perception; Time estimation We describe a quantitative model of timing that generates times of responses (i.e., behavior) given the times of onsets and terminations of stimuli and reinforcers (i.e., the procedure), and determines how information from multiple time-markers (e.g., stimulus onset, stimulus termination, and delivery of reinforcer) are combined to control behavior. From simulated data, a large number of summary measures can be calculated that can be compared with correspond- ing measures obtained from animal experimental data. The behavior of animals is often characterized by clusters of responses (i.e., bouts of responses) such as food searching by rats in an operant chamber (Shull et ∗ Corresponding author. Tel.: +1 401 863 3979; fax: +1 401 863 1300. E-mail address: paulo guilhardi@brown.edu (P. Guilhardi). al., 2001), and the patterns of feeding in cows (Tolkamp and Kyriazaki, 1999). The rates and patterns of bouts are controlled by the particular procedure imposed. The packet theory of timing and conditioning described in this article is a small modification of the one previ- ously used to account for the pattern and rate of bout initiation, and bout characteristics (Kirkpatrick, 2002; Kirkpatrick and Church, 2003). 1. Simple procedures for the study of conditioning and timing Many standard procedures involve multiple time- markers. This section begins with a description of an operant trace procedure involving three time-markers that we proceed to decompose in order to develop the model. 0376-6357/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.beproc.2005.02.004