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Introduction

Hereditarians have been trying to prove the existence of a genetic basis of intelligence for over 100 years. In this time frame, they have used everything from twin, family and adoption studies to tools from the molecular genetics era like GCTA and GWAS. Using heritability estimates, behavior geneticists claim that since intelligence is highly heritable, that there must thusly be a genetic basis to intelligence controlled by many genes of small effect, meaning it’s highly polygenic.

In his outstanding book Misbehaving Science, Panofsky (2014) discusses an attempt funded by the Rockefeller Foundation (RF) at showing a genetic basis to dog intelligence to prove that intelligence had a genetic basis. But it didn’t end up working out for them—in fact, it showed the opposite. The investigation which was funded by the RF showed quite the opposite result that they were looking for—while they did find evidence of some genetic differences between the dog breeds studied, they didn’t find evidence for the existence of a “general factor of intelligence” in the dogs. This issue was explored in Scott and Fuller’s 1965 book Genetics and the Social Behavior of the Dog. These researchers, though, outright failed in their task to discover a “general intelligence” in dogs. Modern-day research also corroborates this notion.

The genetic basis of dog intelligence?

This push to breed a dog that was highly intelligent was funded by the Rockefeller Foundation for ten years at the Jackson Laboratory. Panofsky (2014: 55) explains:

Over the next twenty years many scientists did stints at Jackson Laboratory working on its projects or attending its short courses and training programs. These projects and researchers produced dozens of papers, mostly concerning dogs and mice, that would form much of the empirical base of the emerging field. In 1965 Scott and John Fuller, his research partner, published Genetics and the Social Behavior of the Dog. It was the most important publication to come out of the Jackson Lab program. Scott and Fuller found many genetic differences between dog breeds; they did not find evidence for general intelligence or temperament. Dogs would exhibit different degrees of intelligence or temperamental characteristics depending on the situation. This evidence of interaction led them to question the high heritability of human intelligence—thus undermining a goal of the Rockefeller Foundation sponsors who had hoped to discredit the idea that intelligence was the product of education. Although the behavioral program at Jackson Laboratory declined after this point, it had been the first important base for the new field.

Quite obviously this was the opposite result of what they wanted—dog intelligence was based on the situation and therefore context-dependent.

Scott and Fuller (1965) discuss how they used to call their tests “intelligence tests” but then switched to calling them “performance tests”, “since the animals
seemed to solve their problems in many ways other than through pure thought or
intellect” (Scott and Fuller 1965: 37), while also writing that “no evidence was found for a general factor of intelligence which would produce good performance on all tests” (1965, 328). They also stated that they found nothing like the general intelligence factor in dogs like that is found in humans (1965: 472) while also stating that it’s a “mistaken notion” to believe in the general intelligence factor (1965: 512). They then conclude, basically, that situationism is valid for dogs, writing that their “general impression is that an individual from any dog breed will perform well in a situation in which he can be highly motivated and for which he has the necessary physical capacities” (1965: 512). Indeed, Scott noted that due to the heritability estimates of dog intelligence Scott came to the conclusion that human heritability estimates “are far too high” (quoted in Paul, 1998: 279). This is something that even Schonemann (1997) noted—and it’s “too high” due to the inflation of heritability due to the false assumptions of twin studies, which lead to the missing heritability crisis. One principle finding was that genetic differences didn’t appear early in development, which were then molded by further experience in the world. Behavior was highly variable between individuals and similar within breeds.

The results were quite unexpected but scientifically exciting. During the very early stages of development there was so little behavior observed that there was little opportunity for genetic differences to be expressed. When the complex patterns of behavior did appear, they did not show pure and uncontaminated effects of heredity. Instead, they were extraordinarily variable within an individual and surprisingly similar between individuals. In short, the evidence supported the conclusion that genetic differences in behavior do not appear all at once early in development, to be modified by later experience, but are themselves developed under the influence of environmental factors and may appear in full flower only relatively late in life. (Scott and Fuller, 1965)

The whole goal of this study by the Jackson Lab was to show that there was a genetic basis to intelligence in dogs and that they therefore could breed a dog that was intelligent and friendly (Paul, 1998). They also noted that there was no breed which was far and above the best at the task in question. Scott and Fuller found that performance on their tests was strongly affected by motivational and emotional factors. They also found that breed differences were strongly influenced by the environment, where two dogs from different breeds became similar when raised together. We know that dogs raised with cats showed more favorable disposition towards them (Fox, 1958; cf Feuerstein and Terkel, 2008, Menchetti et al, 2020). Scott and Fuller (1965: 333) then concluded that:

On the basis of the information we now have, we can conclude that all breeds show about the same average level of performance in problem solving, provided they can be adequately motivated, provided physical differences and handicaps do not affect the tests, and provided interfering emotional reactions such as fear can be eliminated. In short, all the breeds appear quite similar in pure intelligence.

The issue is that by believing that heritability shows anything about how “genetic” a trait is, one then inters that there has to be a genetic basis to the trait in question, and that the higher the estimate, the more strongly controlled by genes the trait in question is. However, we now know this claim to be false (Moore and Shenk, 2016). More to the point, the simple fact that IQ shows higher heritability than traits in the animal kingdom should have given behavioral geneticists pause. Nonetheless, it is interesting that this study that was carried out in the 1940s showed a negative result in the quest to show a genetic basis to intelligence using dogs, since dogs and humans quite obviously are different. Panofsky (2014: 65) also framed these results with that of rats that were selectively bred to be “smart” and “dumb”:

Further, many animal studies showed that strain differences in behavior were not independent of environment. R. M. Cooper and J. P. Zubek’s study of rats selectively bred to be “dull” and “bright” in maze-running ability showed dramatic differences between the strains in the “normal” environment. But in the “enriched” and especially the “restricted” developmental environments, both strains’ performance were quite similar. Scott and Fuller made a similar finding in their comparative study of dog breeds: “The behavior traits do not appear to be preorganized by heredity. Rather a dog inherits a number of abilities which can be organized in different ways to meet different situations.” Thus even creatures that had been explicitly engineered to embody racial superiority and inferiority could not demonstrate the idea in any simple way

Psychologist Robert Tryon (1940) devised a series of mazes, ran rats through them and then selected rats that learned quicker and slower (Innis, 1992). These differences then seemed to persists across these rat generations. Then Searle (1949) discovered that the so-called “dumb” rats were merely afraid of the mechanical noise of the maze, showing that Tryon selected for—unknowingly—emotional capacity. Marlowitz (1969) then concluded “that the labels “maze-bright” and “maze-dull” are inexplicit and inappropriate for use with these strains.”

Dogs and human races are sometimes said to be similar, in which a dog breed can be likened to a human race (see Norton et al, 2019). However, dog breeds are the result of conscious human selection for certain traits which then creates the breed. So while Scott and Fuller did find evidence for a good amount of genetic differences between the breeds they studied, they did not find any evidence of a genetic basis of intelligence or temperament. This is also good evidence for the claim that a trait can be heritable (have high heritability) but have no genetic basis. Moreover, we know that high levels of training improve dog’s problem solving ability (Marshall-Pescini et al, 2008, 2016). Further, perceived differences in trainability are due to physical capabilities and not cognitive ones (Helton, 2008). And in Labrador Retrievers, post-play training also improved training performance (Affenzeller, Palme, and Zulch, 2017; Affenzeller, 2020). Dogs’ body language during operant conditioning was also related to their success rate in learning (Hasegawa, Ohtani, and Ohta, 2014). We also know that dogs performed tasks better and faster the more experience they had with them, not being able to solve the task before seeing it demonstrated by the human administering the task (Albuquerque et al, 2021). Gnanadesikan et al (2020) state that cognitive phenotypes seem to vary by breed, and that these phenotypes have strong potential to be artificially selected, but we have seen that this is an error. Morrill et al (2022) found no evidence that the behavioral tendencies of certain breeds reflected intentional selection by humans but could not discount the possibility.

Conclusion

Dog breeds have been used by hereditarians for decades as a model for that of intelligence differences between human races. The analogy that dog breeds and human races are also similar has been used to show that there is a genetic basis for human race, and that human races are thusly a biological reality. (Note that I am a pluralist about race.) But we have seen that in the 40s the study which was undertaken to prove a hereditary basis to dog intelligence and then liken it to human intelligence quite obviously failed. This then led one of the authors to conclude—correctly—that human heritability estimates are inflated (which has led to the missing heritability problem of the 2000s).

Upon studying the dogs in their study, they found that there was no general factor of intelligence in these dogs, and that the situation was paramount in how the dog would perform on the task in question. This then led Scott to conclude that human heritability estimates are too high, a conclusion echoed by modern day researchers like Schonemann. The issue is, if dogs with their numerous breeds and genetic variation defy a single general factor, what would that mean for humans? This is just more evidence that “general intelligence” is a mere myth, a statistical abstraction. There was also no evidence for a general temperament, since breeds that were scared in one situation were confident in another (showing yet again that situationism held here). The failure of the study carried out by the RF then led to the questioning of the high heritability of human intelligence (IQ), which wasn’t forgotten as the decades progressed. Nonetheless, this study casted doubt on the claim that intelligence had a genetic basis.

Why, though, would a study of dogs be informative here? Well, the goal was to show that intelligence in dogs had a hereditary component and that thusly a kind of designer dog could be created that was friendly and intelligent, and this could then be likened to humans. But when the results were the opposite of what they desired, the project was quickly abandoned. If only modern-day behavioral geneticists would get the memo that heritability isn’t useful for what they want it to be useful for (Moore and Shenk, 2016)