Source Paper
Information, certainty, and learning
Harris JA, Gallistel CR
eLife • 2026
Pavlovian Conditioning with Variable CS-US Intervals
Objective: To examine how variable CS-US intervals affect Pavlovian conditioning acquisition and responding patterns using different C/T ratios
Protocol Steps
Housing and food restriction
House rats in groups of 4 and implement food restriction 3 days before experiment
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“Three days before commencing the experiment, they were placed on a restricted food schedule”
Daily feeding schedule
Feed rats daily ration of dry chow equal to 5% of total tub weight 30 minutes after training
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“half an hour after the end of the daily training session, each tub of rats received a ration equal to 5% of the total weight”
Group allocation
Randomly allocate each tub of four rats to one of 14 experimental groups with different C/T ratios
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“Each tub of four rats was randomly allocated to one of the 14 groups shown in Table 1”
Variable CS-US interval setup
Set CS-US intervals to vary trial-to-trial according to uniform distribution centered on group-specific T value
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“the CS-US interval varied from trial-to-trial according to a uniform distribution centred on the value of T”
CS-US interval range
Program intervals to range from minimum of 2s to maximum of 2×T-2s for each group
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“the interval varied from a minimum of 2 s to a maximum of 2x T –2 s”
Inter-trial interval setup
Set ITI to vary trial-to-trial as uniform distribution with minimum of 15s
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“The ITI in each group also varied from trial-to-trial as a uniform distribution with a minimum of 15 s”
Training parameters for Groups 1-11
Conduct 10 trials per session for groups with C/T ratios from 1.5 to 72
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“For the first 11 groups (those with ratios from 1.5 to 72), there were 10 trials per session”
Training parameters for Groups 12-14
Conduct 3 trials per session for groups with C/T ratios of 110, 180, and 300
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“for the remaining three groups (with C / T ratios of 110, 180, and 300), each session contained only three trials”
Daily training schedule
Train all groups with one session per day for total of 42 sessions
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“All groups were trained with one session per day for a total of 42 sessions”
Response recording
Record photo-beam interruptions during each CS and during 10s period before CS onset
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“Photo-beam interruptions by entry into the magazine were recorded during each CS and each ITI (recorded during the 10 s period immediately before CS onset)”