Concept learning and the use of three common psychophysical paradigms in the archerfish (Toxotes chatareus)

Abstract

Archerfish are well known for their specialized hunting technique of spitting water at prey located above the water line. This unique ability has made them a popular focus of study as researchers try to understand the mechanisms involved in targeting and spitting. In more recent years, archerfish have also become an increasingly popular model for studying visual discrimination and learning in general. Until now, only the alternative forced-choice (AFC) task has been used with archerfish, however, they may be capable of learning other classical discrimination tasks. As well as providing alternative, and potentially more efficient, means for testing their visual capabilities, these other tasks may also provide deeper insight into the extent to which an organism with no cortex can grasp the concepts underlying these tasks. In this paper, we consider both the matched-to-sample (MTS) and the odd-one-out (OOO) tasks as they require the subject to learn relatively sophisticated concepts rather than a straight, stimulus-reward relationship, of the kind underlying AFC tasks. A variety of line drawings displayed on a monitor were used as stimuli. We first determined if archerfish could complete the MTS and OOO test and then evaluated their ability to be retrained to new stimuli using a 4-AFC test. We found that archerfish were unable to learn the MTS and had only a limited capacity for learning the OOO task. We conclude that the MTS and OOO are impractical as paradigms for behavioral experiments with archerfish. However, the archerfish could rapidly learn to complete an AFC test and select the conditioned stimulus with a high degree of accuracy when faced with four stimuli, making this a powerful test for behavioral studies testing visual discrimination. In addition, the fish were able to learn the concept of oddity under particular training circumstances. This paper adds to the growing evidence that animals without a cortex are capable of learning some higher order concepts.

Discrimination of human faces by archerfish (Toxotes chatareus)

“…Archerfish have previously been shown capable of discriminating large numbers of stimuli to a similar degree of accuracy (up to 93% accuracy)4142. It seems likely that the archerfish did not use trivial features to discriminate the human faces as the fish could distinguish one face from 44 others which varied in similarity.…”

Same or different? Abstract relational concept use in juvenile bamboo sharks and Malawi cichlids

“…In both cases, individuals chose the appropriate spatial relationship in the respective transfer test in on average 10.4 6 3.61 (i.e., 52%, bamboo sharks) to 13 6 0.63 trials (i.e., 65%, Malawi cichlids). During Training 1, 2, and 3, the stimulus sets were not changed until the learning criterion was reached, allowing individuals to solve the task based on direct association between the food reward and each positive stimulus-a training scheme also used for archerfish by Newport et al (2014Newport et al ( , 2015. Yet, ten individuals of the present study presumably learned the general idea to "choose two different, vertically arranged objects" and were able to transfer this knowledge to the fourth training task (as discussed earlier).…”

“…The formation and manipulation of abstract concepts requires a higher level of cognitive reasoning (Katz et al 2007) and it appears to require time to develop and mature during (human) infancy (Murphy 2004;Mareschal et al 2010 2014, 2015), and bees (Giurfa et al 2001;Avarguès-Weber et al 2012). While harbor seals, echidna, parrots, and pigeons successfully applied learned rules to novel stimuli, other species, including fish, failed to learn the concept (Newport et al 2014(Newport et al , 2015.The general capability to discriminate between a variety of different objects has been thoroughly investigated in bamboo sharks (Chiloscyllium griseum, e.g., Fuss et al 2014aFuss et al , 2014b Schluessel 2015, 2017) as well as in Malawi cichlids (Pseudotropheus zebra, e.g., Schluessel et al 2014a. Juvenile bamboo sharks (Schluessel and Duengen 2015) and Malawi cichlids (Schluessel et al 2012) distinguished visually between two categories ("fish" and "snail") independently of image features or image type (i.e., black and white drawings, photographs, comics, or negative images) in two alternative forced choice experiments.…”

“…Therefore, it has long been suggested that only primates are capable of learning this task. Comparative studies investigating the ability of non-primate species to deal with abstract concepts are currently limited to a small group of species including birds (e.g., pigeons: Blaisdell and Cook 2005;Katz and Wright 2006;parrots: Pepperberg 1987), mammals (dolphins: Mercado et al 2000; sea lions: Kastak and Schusterman;coati: Chausseil 1991; harbor seals: Scholtyssek et al 2013;echidna: Russel and Burke 2016), teleost fish (e.g., Toxotes chatareus: Newport et al 2014Newport et al , 2015, and bees (Giurfa et al 2001;Avarguès-Weber et al 2012). While harbor seals, echidna, parrots, and pigeons successfully applied learned rules to novel stimuli, other species, including fish, failed to learn the concept (Newport et al 2014(Newport et al , 2015.…”

Changing tides: ecological and historical perspectives on fish cognition

“…The nature of the hunting methods of the archerfish also provides a unique tool to access cognitive function, as the archerfish will flexibly learn to shoot at almost any target that will provide a food reward . This opportunity was recently used to begin investigating higher order cognitive capacities of archerfish . Fish were set concept learning tasks, including ‘match‐to‐sample’ or ‘odd‐one‐out’ tasks as well as a four‐way ‘alternative forced‐choice’ task.…”