Jason A.R Carr

Rats use an ordinal timer in a daily time-place learning task.

Rats received 2 daily sessions in a large clear chamber. A lever was mounted on each of the 4 chamber walls. For each rat, a different lever provided food during 0930 and 1530 sessions. The rats learned which lever would provide food at 0930 and 1530. Probe tests suggested that the rats learned to press 1 lever during their 1st session of each day and to then press a 2nd lever during their 2nd session of each day. We propose that this knowledge of the order of a set of events within a period of time constitutes ordinal timing. We contrast the temporal information provided by ordinal, phase, and interval timing and consider why multiple timing systems have evolved in animals.

Chapter 7 Ordinal, phase, and interval timing

Publisher Summary This chapter explores the notion that three broad types of timing systems have evolved in animals: ordinal, phase, and interval timers. It suggests that each type of timing system is specifically adapted to provide animals with a capacity to process a particular type of temporal information. The chapter explores a computational-representational approach, which is used to the study animal cognition, specifically in the temporal information-processing domain. In this chapter, Gallistels approach is described and then each type of timing system within a computational representational framework is characterized. To illustrate the types of temporal-problems that these three types of timing systems are specifically adapted to solve, the chapter reviews the field and laboratory evidence of time-place learning that is accumulated to-date. The chapter suggests that animals possess multiple spatial navigation strategies, each of which is specifically adapted to solve a particular type of spatial problem. These spatial navigation strategies and the spatial problems that they are adapted to solve are discussed.

Field observations of time-place behaviour in scavenging birds

Encoding the spatial location and the time at which significant biological events occur is thought to be a fundamental way in which one form of memory is organized in animals (Gallistel, 1990, The Organization of Learning. MIT Press, Cambridge, MA). If this is true, one would expect to find evidence of this process in a wide variety of animals and in a wide number of situations. We report field observations of scavenging birds at two outdoor locations at which people tend to congregate and eat food, primarily around midday. Scavenging birds appeared to anticipate this peak in food availability and arrived at these locations before the number of people was at a maximum; time of day, not the absolute number of people, was the best predictor of the number of birds at both sites. At a third location where food is not consumed this relationship was not observed. Taken together these observations support the notion that animals represent the spatial and temporal characteristics of biologically important events and use this knowledge to forage efficiently.

Rats are reluctant to use circadian timing in a daily time–place task

On daily time-place learning tasks animals can work for food at different spatial locations during sessions at different times of the day. In previous experiments rats tracked this pattern of food availability with ordinal timing-they learned to respond at the locations in the correct order each day. In contrast, pigeons used circadian timing. In this experiment rats received a mixture of morning session only days, afternoon session only days, and morning and afternoon session days. Under these conditions ordinal timing had low predictive ability, but circadian timing was potentially perfectly predictive of the location of food availability. We thought this procedural change might encourage rats to use circadian timing. However, we found little evidence that rats can use time of day information to track this daily spatiotemporal pattern of food availability. These results are suggestive of differences in the use of circadian clock consultation by rats and pigeons.

Errors made by animals in memory paradigms are not always due to failure of memory

It is commonly assumed that errors in animal memory paradigms such as delayed matching to sample, radial mazes, and food-cache recovery are due to failures in memory for information necessary to perform the task successfully. A body of research, reviewed here, suggests that this is not always the case: animals sometimes make errors despite apparently being able to remember the appropriate information. In this paper a case study of this phenomenon is described, along with a demonstration of a simple procedural modification that successfully reduced these non-memory errors, thereby producing a better measure of memory.

Further evidence that rats use ordinal timing in a daily time-place learning task.

Rats received morning, midday, and afternoon sessions each day in a chamber located in a room containing distal spatial cues. A lever was mounted on each of the four walls. The rats could work for food on a different lever during each of the three sessions. The rats were able to learn the location of food availability during morning, midday, and afternoon sessions. Results obtained after skipped morning, midday, and afternoon sessions support our contention that rats solve this time-place task using ordinal timing, or knowledge of the daily spatiotemporal sequence of food availability. However, during probe sessions when the predicted location of food availability based on ordinal information conflicted with the predictions based on other types of information, behavioural compromise was evident. It appears that rats use multiple types of information, one of which is ordinal timing, to track the location of food availability in the daily time-place task.