Indeed, it is only recently that major cognitive experiments have been conducted on reptiles. Numerous other animals, including mammals, birds, and even fish and cephalopods had been tested, but not reptiles.
There are probably many causes of this, but the fact that reptiles do not have good public relations probably plays a major role. Since cognition in animals first began to be studied, reptiles have always been assumed to be primitive and stupid creatures, vastly inferior in intellect to mammals and birds. And for many centuries, humans have hated reptiles. They were widely seen as abhorrent, and they were often associated with evil. In fact, the following quote is attributed to Carl Linnaeus, widely credited as the father of modern taxonomy: "Reptiles are abhorrent because of their cold body, pale color, cartilaginous skeleton, filthy skin, fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, and terrible venom; wherefore their creator has not exerted his powers to make many of them."
Therefore, studies on reptilian cognition were not really in existence until the late 2000s and early 2010s. And the results of these studies are very different from the stereotypes that most people have about reptiles. Instead, the results paint a very different picture from the slow, dim-witted, unsuccessful reptiles of popular culture.
In one study, anoles were found to perform as well as birds on an experiment which involved hiding food behind a lid, and having the animals find a way to get to it. Anoles usually capture their prey by striking at it from above, but in this situation, the lizards were forced to innovate, and find other ways to gain access to their food. For example, some of them used their snouts as a lever to lift the lid off. This experiment shows that anole lizards are capable of problem-solving.
In other experiments, tortoises were shown to be capable of navigating mazes at least as well as mammals, and monitor lizards have been shown to be capable of counting.
In addition, there is also plenty of anecdotal evidence from pet owners that iguanas are very intelligent, and are capable of being trained, like dogs.
All of this new evidence is startling to most people, who used to underestimate reptiles' intelligence.
And this leads me to ask a question: Are we currently in the midst of a paradigm shift? A paradigm shift is when a major revolution occurs regarding the way the majority of people think about a scientific topic. Charles Darwin's theory of evolution via natural selection in the 19th century was a paradigm shift, as was Albert Einstein's discovery of quantum mechanics in the 20th century. It appears to me that another paradigm shift is currently underway with regard to reptilian intelligence; in the direction of increased intelligence. Rather than slow, dull, primitive creatures, reptiles are now being transformed into intelligent, successful, and elegant animals. And that's good, because that is what they are.