Behavioural Processes 98 (2013) 106–111 Contents lists available at SciVerse ScienceDirect Behavioural Processes journal h om epa ge : www.elsevier.com/locate/behavproc Differential reinforcement of an approach response in zebraﬁsh (Danio rerio) Kazuchika Manabe a,∗ , R.J. Dooling b,1 , Shinichi Takaku c,2 a Graduate School of Social and Cultural Studies, Nihon University, 4-25 Nakatomi-Minami, Tokorozawa, Saitama 359-0003, Japan b University of Maryland, College Park, MD 20742, USA c College of Bioresource Sciences, Nihon University, Fujisawa 252-0880, Japan a r t i c l e i n f o Article history: Received 28 November 2012 Received in revised form 29 April 2013 Accepted 15 May 2013 Keywords: Differential reinforcement Approach response Automated system Food reinforcer Zebraﬁsh a b s t r a c t Five zebraﬁsh were trained to approach a target using a fully automated training procedure. During a training session, if the distance between the ﬁsh and the target was closer than an arbitrarily set distance, the approach response was reinforced by food. The ﬁsh continued to respond under this reinforcement contingency and the distance criterion could be shortened up to eighty times within a 1 h session. The initial distance limit was then shortened for the next test training session. Once the initial distance criterion was reduced to a ﬁnal minimum distance, the distance criterion was ﬁxed at this value for the next nine successive sessions. In a second experiment using different ﬁsh, we manipulated approach distances in three conditions. The ﬁrst condition was identical to the changing criterion training as in Experiment 1. In the second condition, only response distances under a distance criterion were reinforced. And in the last condition, only response distances over the distance criterion were reinforced. Results show that zebraﬁsh can control the distance between themselves and a target. In other words, zebraﬁsh are sensitive to the spatial consequences of their behavior. The present results show that a differential reinforcement paradigm can be successfully applied to zebraﬁsh which therefore enhances their value as a vertebrate model for studies of complex behavior including visuomotor learning. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Zebraﬁsh have many advantages as biomedical animal model. For example, they are easy and inexpensive to maintain, they are proliﬁc breeders, and they reach sexual maturation in about 3 months. Moreover, since the embryos are translucent, investiga- tors are able to easily observe the development of many organ systems. For all of these reasons, the zebraﬁsh is becoming one of the most useful vertebrate models for biomedical investigations. Now behavioral studies have also begun to exploit the potential of zebraﬁsh as a vertebrate model. Learning studies have shown that zebraﬁsh are capable of discriminating visual stimuli (Colwill et al., 2005; Risner et al., 2006), and spatial cues (Eddins et al., 2009; Levin et al., 2003). In addition, these ﬁsh are capable of both avoid- ance learning (Xu et al., 2007; de Castro et al., 2009; Lee et al., 2010; Pradel et al., 2000; Levin et al., 2004) and appetitive learn- ing (Colwill et al., 2005; Manabe et al., 2013; Sison and Gerlai, ∗ Corresponding author. Tel.: +81 4 2996 4171; fax: +81 4 2996 4163. E-mail addresses: manabe.kazuchika@nihon-u.ac.jp (K. Manabe), rdooling@umd.edu (R.J. Dooling), Takaku.shinichi@nihon-u.ac.jp (S. Takaku). 1 Tel.: +1 301 405 5925; fax: +1 301 314 9566. 2 Tel.: +81 046 684 3711; fax: +81 046 684 3711. 2010). Taken together, these studies suggest that zebraﬁsh can be very useful subjects for studies in perception, learning, and higher- order process such as learning set and 3 choice serial reaction time experiments (Parker et al., 2012a,b). In the ﬁelds of neurology and psychiatry, the rodent model has been used to investigate neuroactive drugs (Champagne et al., 2010). The behavioral phenotype has been characterized by oper- ant conditioning using lever pressing. A comparable quantitative measure to lever pressing in the rodent, has not been developed for zebraﬁsh (Brennan, 2011). Recently, we developed an automated system in which zebraﬁsh can be trained to approach to a tip of optical ﬁber repeatedly to get food reinforcer, much like a pressing lever for rodents and pecking response for pigeons (Manabe et al., 2013). This method makes it possible to do comparable studies in both rodent models and zebraﬁsh in a similar way. It has long been known that many animals can learn to differ- entially respond to different contingencies. For example, pigeons can be trained to make spaced responses in time, if only spaced responses are reinforced (Staddon, 1965). Lobster and rats can learn to make only forceful responses if only strong responses are reinforced (Tanimoto et al., 2009; Tomina and Takahata, 2010; McClure et al., 2000). Budgerigars can learn to produce different vocalizations to different visual stimuli (Manabe et al., 1995, 1998). Likewise, response duration in species as diverse as monkeys, rats 0376-6357/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.beproc.2013.05.013