Abstract
Simple SummaryQuantity discrimination involves distinguishing which of two quantities is greater. This discrimination between larger and smaller quantities has only been demonstrated in rats post extensive training. We tested whether domestic rats could perform quantity discrimination without explicit training. We found that rats could distinguish the greater amount in comparisons of 1 vs. 2, 2 vs. 3, 3 vs. 5, 3 vs. 8, 4 vs. 6, and 4 vs. 8. Rats could not distinguish between 3 vs. 4, 4 vs. 5 and 5 vs. 6. We also found that as the ratio between quantities became finer the choice of the larger quantity decreased. We conclude that rats can perform quantity discrimination without extensive training and that their quantity discrimination ability is influenced by the ratio between quantities.Quantity discrimination is a basic form of numerical competence where an animal distinguishes which of two amounts is greater in size. Whilst quantity discrimination in rats has been investigated via training paradigms, rats’ natural quantity discrimination abilities without explicit training for a desired response have not been explored. This study investigated domestic rats’ ability to perform quantity discrimination. Domestic rats (n = 12) were examined for their ability to distinguish the larger amount under nine quantity comparisons. One-sample t-tests identified a significant preference for the larger quantity in comparisons of 1 vs. 2, 2 vs. 3, 3 vs. 5, 3 vs. 8, 4 vs. 6, and 4 vs. 8. No preference between quantities was found for comparisons of 3 vs. 4, 4 vs. 5 and 5 vs. 6. Overall, this study drew two key conclusions. Firstly, that domestic rats are capable of performing quantity discrimination without extensive training. Secondly, as subjects adhered to Weber’s law, it was concluded that the approximate number system underpins domestic rats’ ability to perform spontaneous quantity discrimination.
Highlights
The ability to discriminate between different quantities can improve survival and reproductive success in a range of contexts for instance by enabling animals to monitor and compare the number of predators, group members, food items available or competitors [1]
The approximate number system is an analog magnitude system associated with adherence to Weber’s law, where quantity discrimination ability is influenced by the ratio between quantities [22,25,26]
This study explored whether rats utilize the object-file system or approximate number system when discriminating quantities
Summary
The ability to discriminate between different quantities can improve survival and reproductive success in a range of contexts for instance by enabling animals to monitor and compare the number of predators, group members, food items available or competitors [1]. Animals 2016, 6, 46 animals perform quantity discrimination, the object-file system and the approximate number system ( termed the analog magnitude mechanism) [21,22]. The object-file system is perceived to be employed if the animal cannot distinguish between two amounts containing in excess of three to four items [22,23,24]. The approximate number system is an analog magnitude system associated with adherence to Weber’s law, where quantity discrimination ability is influenced by the ratio between quantities [22,25,26].
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