Some authors argue that brain size correlates with cognitive abilities. However, the few studies so far that assessed cognitive abilities in Asian elephants (Elephas maximus) showed mixed results depending on the type of task and the sensory system involved (Cozzi et al., 2001; Hart and Hart 2007; Plotnik et al. 2011).

Behavioral evidence suggests that Asian elephants strongly rely on their sense of smell in a variety of contexts including foraging and social communication (Langbauer 2000; Rasmussen 2006; Rasmussen and Krishnamurthy 2000; Santiapillai and Read, 2010; Scott and Rasmussen 2005; Sukumar 2003; Vidya and Sukumar 2005). The behavior of Asian elephants has been studied in some detail and suggests that chemical communication is an important part in their social interactions (Rasmussen 1999; Rasmussen 2006; Rasmussen 1998; Rasmussen and Krishnamurthy 2000; Rasmussen and Schulte 1998; Schulte et el. 2005). In fact, the elephant is one of the few mammal species so far for which a sex pheromone has been chemically identified and functionally verified (Rasmussen et al. 1997, 2005). Anatomical evidence of well-developed olfactory and vomeronasal systems (Göbbel et al. 2004; Johnson and Rasmussen 2002; Koikegami et al. 1941; Shoshani et al. 2006) as well as of specialized skin glands (Lamps et al. 2001; Wheeler et al. 1982) further supports the idea that the sense of smell plays a crucial role in regulating the behavior of elephants.

Until recently, however, no behavioral test existed which would allow us to systematically assess the olfactory capabilities in this species. Asian elephants have successfully been trained in two-choice visual (Rensch 1957); Rensch and Altevogt 1955; Nissani et al. 2005), auditory (Heffner and Heffner 1982) and tactile (Dehnhardt et al. 1997) discrimination tasks. A previous study by Arvidsson et al. (2012) developed and successfully applied an olfactory discrimination paradigm for Asian elephants and collected first data on learning speed, olfactory memory and olfactory discrimination performance. The paradigm is based on a food-rewarded two-alternative operant conditioning procedure. The animals learned to sniff at two odor ports and were food-rewarded when they performed an operant response (placing the tip of the trunk at a certain position of the experimental set-up) upon correctly identifying the rewarded odor. The study showed that Asian elephants indeed have fast learning abilities and a good olfactory memory.

Similar operant conditioning procedures to assess olfactory learning capabilities and olfactory long-term memory have been employed with other mammals such as squirrel monkeys (Laska and Hudson 1993), spider monkeys (Laska et al. 2003), pigtail macaques (Hübener and Laska, 2001), South African fur seals (Laska et al. 2008), mice (Bodyak and Slotnick 1999), rats (Slotnick et al. 1991), and dogs (Lubow et al. 1973). This allows for direct comparisons of olfactory learning performance and olfactory long-term memory performance between species.