Short-term Memory Testing in Domestic Horses: Experimental Design Plays a Role

This study investigated whether four horses could recall the location of a food objective in a two-choice delayed response test. During testing, horses stood unrestrained in a station where they observed the delivery of 30 g of grain into one of two containers. They were then released and allowed to go toward a container under the following contexts: immediate release or delayed release of 5, 10, 15, 20, or 30 seconds. Results showed that horses remembered the correct objective not only under the immediate release condition but also for all delayed release conditions tested. Observational data were also collected to determine whether the horses were indeed relying on memory to solve the delayed response problems or whether they were using orienting cues to maintain focus on the correct container. These data showed that the horses did not maintain visual contact with the objective during many of the trials; instead, they attended to an assortment of distractions in the surrounding area. Contrary to a previous report in which horses could not accurately respond in a similar situation after 10-second delays, these findings suggest that at least some horses are not as limited with respect to their ability to recall things and have an adequate spatial short-term memory. Experimental design seems to play a significant role in the outcome of this type of research.