How intelligent are various creatures, from our pets to other species? This fundamental question often arises in competitive, humorous, or respectful contexts. One might assume that scientists have developed reliable methods over the years to measure the intelligence of animals deemed less intelligent. Yet, it appears that our cleverest individuals might have consistently been outsmarted by the very subjects they seek to evaluate. Alternatively, it could be that understanding intelligence itself is a formidable challenge.

1. Human Intelligence Assessments Evaluating human intelligence is a contentious issue intertwined with political, ethical, and social debates. The first standardized intelligence assessments were introduced in the late 19th century by Francis Galton, a relative of Charles Darwin, whose legacy also includes eugenics—a concept that has led to severe human rights abuses. These tests gained prominence during World War I, facilitating the assignment of military recruits, particularly for officer roles.

Galton initiated a psychometric center for human intelligence testing, which eventually spurred controversies about racial biases in intelligence assessments, notably highlighted in the 1994 book "The Bell Curve," which erroneously linked intelligence to race. It's crucial to recognize that IQ tests don't measure intelligence directly but are influenced by socioeconomic factors, health, and other variables—similar to the challenges faced in evaluating animal intelligence.

Research in psychometrics has proposed a general intelligence factor, referred to as "g," which reportedly influences individual performance across various tasks. While this remains a topic of debate, it has prompted inquiries into whether such a factor exists in animals. In this discussion, we will focus solely on non-human intelligence.

2. Evaluating Animal Intelligence Recent studies have examined the intelligence of ravens—some of the most cognitively advanced animals—comparing them to chimpanzees, often considered the benchmark for non-human intelligence. A notable review highlighted the limitations of existing intelligence tests, which merit further exploration.

One of the premier methods for assessing animal intelligence is the Primate Cognition Test Battery (PCTB), crafted by Esther Herrmann at the Max Planck Institute for Evolutionary Anthropology. Let's explore how specific tests within this battery are administered, such as those conducted with lemurs:

The initial test in this video evaluated spatial memory, as described in the journal PLOS:

“…Three cups were positioned in a line on a platform before the testing enclosure. The experimenter presented two rewards to the subject, placing them under two of the three cups in clear view. The platform was then moved toward the subject, allowing it to make two choices in succession. If the subject selected an empty cup first, it could not make further choices. A response was deemed correct if both baited cups were chosen in order…”

Through such tests, Herrmann found that a two-and-a-half-year-old human child possesses comparable cognitive abilities regarding the physical environment as a ten-year-old chimpanzee. However, when it comes to social intelligence, human children significantly outperform both chimpanzees and orangutans.

The PCTB encompasses various tasks for testing physical intelligence, including:

• Spatial memory
• Object permanence
• Rotation
• Transposition
• Relative numbers
• Addition
• Noise discrimination
• Shape recognition
• Tool utilization
• Understanding tool properties

Similarly, the tasks designed to assess social intelligence include:

• Social learning
• Comprehension
• Pointing
• Attention state
• Gaze-following
• Understanding intentions

These primate assessments have yet to reveal a general intelligence factor akin to that of humans, instead identifying distinct intelligence domains, indicating that social and physical intelligence may operate as separate entities.

3. Key Limitations… The researchers behind the corvid intelligence tests revealed notable constraints within their methodology and the broader field of animal intelligence evaluation:

• The PCTB presupposes a division between social and physical intelligence, which may not be accurate.
• Interaction between the subject and the tester could undermine the tests' validity.
• Current testing may overlook entirely different cognitive mechanisms that drive behavior.

While examining the limitations of intelligence tests may seem unproductive, doing so is essential for refining the tools we use to understand animal intelligence. It is crucial to view these tests as technological instruments designed to characterize cognitive abilities. Critical analysis of their boundaries is necessary for advancement.

4. Dissecting Social and Physical Intelligence… The PCTB's assumption of a natural divide between social and physical intelligence is logically appealing, yet reanalysis of chimpanzee and child data disproved this notion. Herrmann et al. revisited their earlier work, revealing that their original hypothesis about cognitive skills being divided into two independent domains was flawed. Their subsequent analysis indicated an additional factor—spatial cognition—and demonstrated that social and physical cognitions are interconnected.

This insight sparked discussions on enhancing animal intelligence assessments. A 2016 study highlighted that improvements in cognitive tests are vital, as systemic factors could skew conclusions about the evolution of intelligence. For instance, research on New Caledonian crows illustrated how training impacts performance in self-control tests, emphasizing that pre-existing skills may dictate outcomes rather than inherent intelligence.

Further studies have advocated for refining cognitive assessments, focusing on task design, targeted cognitive domains, and species selection. Unlike human intelligence assessments reliant on language, animal intelligence must be evaluated through behavioral observations, which complicates the interpretation of results.

5. The Tester-Subject Dynamic… The competitive social dynamics of ravens can affect testing outcomes. Hand-raised ravens may perceive experimenters as rivals for resources, potentially overshadowing the effects of intelligence in performance. Similarly, primates experience competitive environments, necessitating the inclusion of such factors in experimental designs.

Past research suggests that the interactions between laboratory staff and primates could influence behavior during tests, complicating the distinction between intelligence assessment and social interaction. Notably, disparities in test outcomes between ravens and parrots may stem from differences in human interaction during assessments.

Ravens’ ability to track gaze is another factor that complicates intelligence testing. Given their competitive nature, they have likely developed skills to follow the gaze of other ravens, which might not accurately reflect their intelligence but rather their gaze-following capabilities.

6. Understanding the Wiring of Intelligence… While ravens display comparable experimental scores to great apes, researchers did not claim that their intelligence is analogous. Similar behaviors can arise from different cognitive architectures. Studies have noted that corvids and primates may solve problems with similar speed and adaptability, yet the underlying cognitive mechanisms remain largely unclear.

The question of how intelligence evolved separately across species is intricate, particularly given the distinct neurological architectures of birds and mammals. Despite divergent evolutionary paths, both groups exhibit remarkable cognitive capabilities, making it essential to understand the biology guiding their cognitive functions.

7. Looking Ahead… Currently, our most astute cognitive scientists find themselves outsmarted by the intelligent animals they study. While we recognize that intelligence exists, we lack clarity on how it operates and is structured. Without a precise definition, designing effective assessments is inherently challenging.

We often create intelligence tests based on assumptions about its components, only to realize that our initial ideas may be flawed. Progress in this field is gradual, akin to navigating in darkness, as we strive to illuminate our understanding of intelligence. Although we may encounter setbacks, such is the nature of scientific inquiry—initial explorations often occur in obscurity, leading us toward new discoveries.

This journey embodies the intrigue and allure of science as we continue to unravel the mysteries of the world around us.