Salamanders (Plethodon cinereus) go for more: rudiments of number in an amphibian

Abstract

Techniques traditionally used in developmental research with infants have been widely used with nonhuman primates in the investigation of comparative cognitive abilities. Recently, researchers have shown that human infants and monkeys select the larger of two numerosities in a spontaneous forced-choice discrimination task. Here we adopt the same method to assess in a series of experiments spontaneous choice of the larger of two numerosities in a species of amphibian, red-backed salamanders ( Plethodon cinereus). The findings indicate that salamanders "go for more," just like human babies and monkeys. This rudimentary capacity is a type of numerical discrimination that is spontaneously present in this amphibian.

When quantity trumps number: discrimination experiments in cotton-top tamarins (Saguinus oedipus) and common marmosets (Callithrix jacchus)

“…First, these studies provide the first systematic investigation showing that non-human animals quantify over sets on the basis of total amount of food rather than number. Again, many other studies have assumed that animals quantify using amount and even demonstrated that non-numerical features such as item size and orientation influence quantity discrimination (Anderson et al 2005;Beran 2001;Call 2000;Menzel 1960;Rumbaugh et al 1987;Thomas and Chase 1980;Uller et al 2003). These studies, however, have not excluded the possibility that animals could combine amount and number information to judge quantity.…”

“…Many of these studies have focused on relative numerosity-discriminations of which of two sets is larger (Anderson et al 2005;Beran 2001;Call 2000;Menzel 1960;Rumbaugh et al 1987;Thomas and Chase 1980;Uller et al 2003)-and the cues used to discriminate stimuli, such as numerical distance, numerical ratio, item size, item orientation, etc. For instance, in a series of studies on the effect of stimulus properties on choice, Menzel (1960Menzel ( , 1961Menzel ( , 1969 demonstrated that chimpanzees are very sensitive to differences in the size of food items (detecting 5% differences in length), but this sensitivity is modulated by the orientation of the food.…”

Iconic and non-iconic stages in number development: the role of language

“…9-14 and overviews in 2,4], and recent evidence suggests that a rudimentary capacity to distinguish small numerosities might even be present in amphibians [15]. This indicates that cardinality can be grasped by nonhuman animals -that is, species that do not possess the human language faculty as part of their biological heritage [16] -and should hence be independent of language.…”

Do cleaner fish learn to feed against their preference in a reverse reward contingency task?

“…Many species such as chimpanzees, Pan troglodytes (Boysen and Berntson 1995), Japanese macaques, Macaca fuscata (Silberberg and Fujita 1996), squirrel monkeys, Saimiri sciureus (Anderson et al 2000), cottontop tamarins, Saguinus oedipus (Kralik et al 2002), rhesus macaques, Macaca mulatta (Murray et al 2005) and two species of prosimians, black and brown lemurs, Eulemur fulvus and E. macaco (Genty et al 2004) showed an initial preference for the larger quantity of food. Such discrimination between two quantities of food could also be shown in red-backed salamanders (Plethodon cinereus) (Uller et al 2003). However, these species did not succeed in spontaneously selecting the smaller reward in order to receive the larger one.…”