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

Abstract

Sorting objects and events into categories and concepts is an important cognitive prerequisite that spares an individual the learning of every object or situation encountered in its daily life. Accordingly, specific items are classified in general groups that allow fast responses to novel situations. The present study assessed whether bamboo sharks Chiloscyllium griseum and Malawi cichlids Pseudotropheus zebra can distinguish sets of stimuli (each stimulus consisting of two abstract, geometric objects) that meet two conceptual preconditions, i.e., (1) "sameness" versus "difference" and (2) a certain spatial arrangement of both objects. In two alternative forced choice experiments, individuals were first trained to choose two different, vertically arranged objects from two different but horizontally arranged ones. Pair discriminations were followed by extensive transfer test experiments. Transfer tests using stimuli consisting of (a) black and gray circles and (b) squares with novel geometric patterns provided conflicting information with respect to the learnt rule "choose two different, vertically arranged objects", thereby investigating (1) the individuals' ability to transfer previously gained knowledge to novel stimuli and (2) the abstract relational concept(s) or rule(s) applied to categorize these novel objects. Present results suggest that the level of processing and usage of both abstract concepts differed considerably between bamboo sharks and Malawi cichlids. Bamboo sharks seemed to combine both concepts-although not with equal but hierarchical prominence-pointing to advanced cognitive capabilities. Conversely, Malawi cichlids had difficulties in discriminating between symbols and failed to apply the acquired training knowledge on new sets of geometric and, in particular, gray-level transfer stimuli.Key words: visual concept learning, spatial arrangement, relational abstract concept, Malawi cichlid, bamboo shark Concepts and categories benefit an individual's cognitive economy by obviating the learning of every particular object or situation encountered in its daily life (e.g., Lamberts and Shanks 1997;Mareschal et al. 2010). Instead, any new object or action is immediately placed in a group of similar, already classified items, which allows for prompt identification and therefore quick response to novel situations. Concept learning (also known as category learning or concept attainment) requires the learner to compare and contrast groups or categories that comprise possibly concept-relevant features with groups or categories that do not comprise these features (Bruner et al. 1967). While items within a group or category can vary to some extent, they all must share at least some item-specific (e.g., physical or perceptually similar) features and the development of prototypes, schemas, attributions, or exemplars predictive of the appropriate category (Zentall et al. 2002). Abstract concepts, in contrast, are not based on item-specific features but on relationships and are therefore not associated...

Abstract concept learning in fish

“…It includes a clear explanation of different concept types and a brief discussion of the use of other sensory modalities when designing concept learning tests for different species. * [28] Abstract concept learning was not directly tested in this study but spontaneous application of the concept of same/different could be one explanation for the decisions of bamboo sharks in a two-alternative forced-choice task with novel stimuli. * [41] This is a comprehensive review of the visual and cognitive challenges associated with the unique hunting strategy of archerfish.…”

“…were presented with a two-alternative forced-choice task (2AFC), in which stimuli were two image pairs with differing spatial arrangements (Fig. 2) [28]. During training, both alternatives had identical symbols that made different pairs, and the vertically stacked pair was always rewarded.…”

“…Another option to direct the attention of subjects is to increase the effort required to make a stimulus selection. In experiments with fish, individuals have been presented with two choices and have had to move into a particular response area (goldfish [20], Malawi cichlids [25,28]), press stimuli with their mouth/nose (goldfish [19], bamboo sharks [28]), or shoot a jet of water at stimuli (archerfish [21,23]) to make a selection. Observing responses that require high effort are not common in fish, but there are some examples that have resulted in successful stimuli discrimination.…”

“…[20,21,23,25,28] and not drawn to scale. In all experiments, stimuli can appear as both the rewarded target and the unrewarded distractor, except in the experiment by [28] in which only one stimulus pair is rewarded (indicated by *). For this experiment, only a selection of transfer stimuli have been illustrated.…”

Counting on Numbers—Numerical Abilities in Grey Bamboo Sharks and Ocellate River Stingrays

“…Several elasmobranch species, including the grey bamboo shark ( Chiloscyllium griseum ) and the ocellate river stingray ( Potamotrygon motoro ), have been part of a range of cognition experiments and have shown various visual discrimination as well as orientation abilities (see reviews [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]). Adding to that, freshwater stingrays ( Potamotrygon castexi ) are able to use water as a tool to extract food from a tube [ 54 ].…”