Supplementary Material for: “Cleaner fish Labroides dimidiatus discriminate numbers but fail a Mental Number Line test.”

Authors: Zegni Triki* and Redouan Bshary

Authors’ affiliation: Behavioral Ecology Laboratory, Faculty of Science, University of Neuchâtel, Emile-Argand 11, 2000 Neuchâtel, Switzerland

* Corresponding author: Zegni Triki, phone number: +41795244902; email address:

ORCID: 0000-0001-5592-8963

Supplementary information about animals used in the present experiment:

Before the numbering task, cleaners were tested in two other cognitive experiments. The two earlier experiments were learning tasks that capture key features of natural interactions with client reef fish. The “bystander effect task” consisted of evaluating the cleaners’ ability to adjust feeding against their preferences to get access to a bystander plate (Bshary and Grutter 2006). The task lasted for four days, including initial training. The “biological market task” (Wismer et al. 2014) was used to assess the cleaners’ ability to learn to choose an ephemeral food source over a permanent one in a maximum of 200 trials over ten days (Salwiczek et al. 2012; Wismer et al. 2014). The two experiments involved feeding off Plexiglas plates, but success was not by any means linked to identifying a location or numbering patterns. After the two experiments, cleaners had a break of one day before we started the training for the numbering task experiment.

Figure S1. (A) example of the non-controlled set of contrasts 2, 5 and 8 elements presented on panelsin the initial test in Experiment I, and Experiment II. (B) an example of a controlled set of the contrasts (2, 5 and 8 elements) used in the control test in Experiment I, here the set is controlled for cumulative surface area and density of the elements. (C) anexample of a controlled set of the contrasts used in the control test in Experiment I, here the set is controlled for cumulative surface area and overall space.(C) front view of a plate depicting 5 elements. (E) aside view of the back of the plate where one plate has accessible food item and the second has inaccessible food item, used in the trials with a food reward. However, during tests without food reward, no food items were placed on the back of the plates.

Table S1. Key features of the experimental design

Category / Rugani et al. (2015) / Present study
Animal species of the study / Domestic chicken Gallus gallus / Cleaner wrasse Labroides dimidiatus
Age / Three days / Adult stage
Sample size for Experiment 1 / N=15 / N=40
Training target / Panel with 5 depicted elements / Panel with 5 depicted elements
Low number test / Panel with 2 depicted elements / Panel with 2 depicted elements
Large number test / Panel with 8 depicted elements / Panel with 8 depicted elements
Training sessions / 20 successful sessions / 20 successful sessions
Time lapse between training and the first test / 2 hours / 2 hours
Time lapse between the two tests / One hour after the first test without extra training sessions / One hour after the first test without extra training sessions
Use of barriers / Opaque and Transparent / Opaque and Transparent
Criteria of end of a test trial / Chicken enters behind the panel with its 2/3 body / Fish swims behind the panel
Test arena / One test arena for all the chicken / Fish tested in their home aquaria to avoid inducing a confinement stress
Testing prior the Numbering task / None / Cognitive tasks: image-scoring and the biological market tasks (see text above)
Number of trials per test / 5 trials / 5 trials

References:

Bshary R, Grutter AS (2006) Image scoring and cooperation in a cleaner fish mutualism. Nature 441:975–978. doi: 10.1038/nature04755

Rugani R, Vallortigara G, Priftis K, Regolin L (2015) Number-space mapping in the newborn chick resembles humans’ mental number line. Science 347:534–536.

Salwiczek LH, Prétôt L, Demarta L, et al (2012) Adult Cleaner Wrasse Outperform Capuchin Monkeys, Chimpanzees and Orang-utans in a Complex Foraging Task Derived from Cleaner – Client Reef Fish Cooperation. PLoS ONE 7:e49068. doi: 10.1371/journal.pone.0049068

Wismer S, Pinto AI, Vail AL, et al (2014) Variation in Cleaner Wrasse Cooperation and Cognition: Influence of the Developmental Environment? Ethology n/a-n/a. doi: 10.1111/eth.12223

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