Automated Operant Conditioning Devices for Fish. Do They Work?

Abstract

The growing use of teleosts in comparative cognition and in neurobiological research has prompted many researchers to develop automated conditioning devices for fish. These techniques can make research less expensive and fully comparable with research on warm-blooded species, in which automated devices have been used for more than a century. Tested with a recently developed automated device, guppies (Poecilia reticulata) easily performed 80 reinforced trials per session, exceeding 80% accuracy in color or shape discrimination tasks after only 3–4 training session, though they exhibit unexpectedly poor performance in numerical discrimination tasks. As several pieces of evidence indicate, guppies possess excellent numerical abilities. In the first part of this study, we benchmarked the automated training device with a standard manual training procedure by administering the same set of tasks, which consisted of numerical discriminations of increasing difficulty. All manually-trained guppies quickly learned the easiest discriminations and a substantial percentage learned the more difficult ones, such as 4 vs. 5 items. No fish trained with the automated conditioning device reached the learning criterion for even the easiest discriminations. In the second part of the study, we introduced a series of modifications to the conditioning chamber and to the procedure in an attempt to improve its efficiency. Increasing the decision time, inter-trial interval, or visibility of the stimuli did not produce an appreciable improvement. Reducing the cognitive load of the task by training subjects first to use the device with shape and color discriminations, significantly improved their numerical performance. Allowing the subjects to reside in the test chamber, which likely reduced the amount of attentional resources subtracted to task execution, also led to an improvement, although in no case did subjects match the performance of fish trained with the standard procedure. Our results highlight limitations in the capacity of small laboratory teleosts to cope with operant conditioning automation that was not observed in laboratory mammals and birds and that currently prevent an easy and straightforward comparison with other vertebrates.

Zebrafish excel in number discrimination under an operant conditioning paradigm

“…Each subject was individually maintained for the duration of the experiment in a glass tank (22 × 50 × 32 cm) filled with 28 L of water (see Gatto et al 2021;Santacà et al 2021 for more details). Two trapezoidal structures (10 × 6 × 32 cm) made with transparent acetate sheets subdivided the tank in an hourglass-shaped testing compartment and two small lateral compartments (Fig.…”

“…In two separate studies, it was found that guppies discriminate numbers that differ by 1 unit up to 4 versus 5 items, corresponding to a 0.80 numerosity ratio (Bisazza et al 2014;Gatto et al 2021). As humans and some other mammals and birds (Mix et al 2002;Rugani et al 2013;Tomonaga 2008), guppies can integrate numerical and nonnumerical information to obtain a more accurate estimate but, if prevented from accessing the latter, they can discriminate based on the sole numerical information (Gatto et al 2021).…”

“…In two separate studies, it was found that guppies discriminate numbers that differ by 1 unit up to 4 versus 5 items, corresponding to a 0.80 numerosity ratio (Bisazza et al 2014;Gatto et al 2021). As humans and some other mammals and birds (Mix et al 2002;Rugani et al 2013;Tomonaga 2008), guppies can integrate numerical and nonnumerical information to obtain a more accurate estimate but, if prevented from accessing the latter, they can discriminate based on the sole numerical information (Gatto et al 2021). The numerical acuity shown by guppies is lower compared to humans, non-human primates and crows but exceeds that observed in cartilaginous fishes, amphibians, reptiles and various warm-blooded vertebrates such as dogs (Canis lupus familiaris), horses (Equus caballus) and domestic chicken (Gallus gallus) (reviewed in Agrillo and Bisazza 2018).…”

“…In this study, we examined the ability of male and female zebrafish to discriminate the larger or the smaller of two numerosities using an appetitive conditioning paradigm and stimuli controlled for the main non-numerical variables. Different methods often yield different results (Bánszegi et al 2016;Gatto et al 2021;Howard et al 2019), and interspecific differences in numerical abilities might be attributable to differences in the methodologies used in the different studies. Here, we adopted the same procedure employed recently in a study in guppy so that a direct comparison with this species was possible (Gatto et al 2021).…”

“…Different methods often yield different results (Bánszegi et al 2016;Gatto et al 2021;Howard et al 2019), and interspecific differences in numerical abilities might be attributable to differences in the methodologies used in the different studies. Here, we adopted the same procedure employed recently in a study in guppy so that a direct comparison with this species was possible (Gatto et al 2021). Subjects were given a series of discriminations of increasing difficulty (from 2 versus 3 items to 5 versus 6 items) to determine their numerical acuity threshold.…”