A delay to reinforcement has been found in previous studies to influence the effectiveness of a reinforcer. As the delay duration increases, response rates decrease and post reinforcement pause durations increase. The present study tested whether it was the increase in time between the effective response and delivery of reinforcement, or, the increases in intervals between reinforcers that devalue the reinforcer. This study also compared the ability of two demand equations and MPR to predict response rates when effort required was changed. The effects of varying delay to reinforcement and intertrial interval on behaviour was examined while the time available for responding was kept constant. There were four conditions; 4-s ITI, 4-s delay, 16-s ITI and 16-s delay, and 6 hens responded under each of these conditions in an ascending geometric series of fixed ratio (FR) values. It was shown that hens generally responded at a faster rate in the ITI conditions than the equivalent delay conditions and peak response rates were seen highest in the 16-s ITI condition in accordance with the demand data. The data was described well by both the demand equations and the MPR equation. While there were inconsistencies among the parameters, there was a moderately strong positive relationships between the parameter values of as and α in the 16-s ITI (r = .51, p = 0.29) and delay (r = .44, p = .44) conditions.