Pigeons' memory for number of events: Effects of intertrial interval and delay interval illumination

Pigeons’ memory for sequences of light flashes when gap duration is an unreliable discriminative cue

“…Spetch and Wilkie referred to this result as the choose-short effect, because pigeons show a bias to peck the comparison stimulus associated with the short sample as the delay interval is extended beyond baseline training. This result has been reported in a large number of studies (Fetterman, 1995;Gaitan & Wixted, 2000;Grant, 1993Grant, , 2006Grant & Kelly, 1996Grant & Spetch, 1991, 1993Grant, Spetch, & Kelly, 1997;Kelly & Spetch, 2000;Kraemer, Mazmanian, & Roberts, 1985;Santi, Bridson, & Ducharme, 1993;Santi, Ducharme, & Bridson, 1992;Sherburne, Zentall, & Kaiser, 1998;Spetch, 1987;Spetch & Rusak, 1989.Memory for number of events has also been studied by training pigeons in a DSMTS procedure (Fetterman, 2000;Fetterman & MacEwen, 1989;Hope & Santi, 2004;Roberts, Macuda, & Brodbeck, 1995;Santi & Hope, 2001). In the studies by Roberts et al and Santi and Hope, pigeons were presented with sample stimuli consisting of two flashes of light in 4 sec (2f/4) or eight flashes of light in 4 sec (8f/4).…”

“…Memory for number of events has also been studied by training pigeons in a DSMTS procedure (Fetterman, 2000;Fetterman & MacEwen, 1989;Hope & Santi, 2004;Roberts, Macuda, & Brodbeck, 1995;Santi & Hope, 2001). In the studies by Roberts et al and Santi and Hope, pigeons were presented with sample stimuli consisting of two flashes of light in 4 sec (2f/4) or eight flashes of light in 4 sec (8f/4).…”

“…If a constant delay interval (e.g., 5 or 10 sec) is used during baseline training in either a number (Santi & Hope, 2001) or a duration (Spetch, 1987) discrimination, then the introduction of shorter delay intervals during testing results in a choosemany effect for number samples and a choose-long effect for duration samples. Hope and Santi (2004) examined pigeons' memory for number of feeder light flashes, varying the ambient chamber illumination during the intertrial interval (ITI) and the delay interval. In Experiment 2, they found that pigeons tested at shorter or longer illuminated delays after having received baseline training with a 5-sec illuminated delay interval produced patterns of response biases dissimilar to those previously obtained with dark delays.…”

“…Thus, pigeons may have coded the number samples by timing and summing f lash duration, as opposed to using an event switch to count the number of feeder light flashes. If this interpretation is correct, then the studies by Roberts et al (1995), Santi and Hope (2001), and Hope and Santi (2004) were not studies examining memory for number, but studies of memory for event duration. Table 1 identifies the temporal and numerical features of the few and many samples used in previous studies of memory for number in the pigeon.…”

Pigeons (Columba livia) associate time intervals with symbols in a touch screen task: Evidence for ordinality but not summation.

“…Testing was conducted 5 days a week between 9 am and 6 pm. The birds had previously been trained in a standard operant chamber to discriminate between sequences of light flashes that varied in number but not in time and in time but not in number (Hope & Santi, 2004; Santi & Hope, 2001), but they had no previous training in a touch screen apparatus to discriminate symbols associated with either different delays to reward or different reward durations.…”