Why a universal definition of intelligence is impossible

Robert J. Sternberg, an influential psychologist and psychometrician known for his extensive work on intelligence , has published an article: “What is intelligence, really? The futile search for a Holy Grail” (2024). In this piece, Sternberg, Professor of Human Development at Cornell University, rethinks the nature of intelligence and criticizes the ongoing search for an all-encompassing definition of intelligence.

Pioneers in intelligence research

Sternberg compares the search for the right definition to the search for the Holy Grail. The term “Holy Grail” refers to a legendary and elusive object from medieval mythology, which symbolizes an ultimate but unattainable quest. Sternberg uses this metaphor to illustrate the fruitless efforts of scientists who try to find a definitive and universal definition of intelligence. He describes ideas of pioneers in thinking about intelligence:

• Sir Francis Galton and James McKeen Cattell attempted to measure intelligence using psychophysiological tests that focused on sensory abilities such as reaction time and perceptual accuracy. These early approaches failed to find strong correlations with practical outcomes such as academic success.
• Alfred Binet and Théodore Simon introduced a new approach by defining intelligence as the ability to make good judgments, to think practically, and to adapt to new circumstances. Their tests, focused on higher cognitive processes, were more successful in predicting school performance.
• Charles Spearman then introduced the g-factor, a general intelligence factor that explains performance across various cognitive tasks.

Recent theories and approaches

Sternberg then mentions more recent attempts to define intelligence.

• Research on working memory has shown that it correlates strongly with intelligence tests. Studies by Daneman and Carpenter emphasize the importance of working memory in cognitive tasks. Some researchers, such as Kyllonen and Christal, even suggest that working memory and intelligence are virtually synonymous, although this remains a matter of debate.
• Howard Gardner (2011) argues that intelligence is not a single entity, but consists of eight relatively independent intelligences: linguistic, logical-mathematical, spatial, musical, naturalistic, bodily-kinesthetic, interpersonal, and intrapersonal intelligence. However, there is little modern empirical evidence for this theory, as abilities are often correlated rather than independent.
• Robert Sternberg (1997, 2021) considers intelligence as a combination of different aspects: creative, analytical and practical intelligence, as well as wisdom. Each aspect plays a specific role in generating, evaluating and applying ideas and in striving for an ethical common good.

Why is there no accepted definition of intelligence yet?

Sternberg proposes four possible explanations for why we have not found a clear definition of intelligence:

1. All theories are wrong: No theory is completely right; intelligence is too complex to fully understand.
2. All theories are correct from their own perspective: Each theory offers valuable insights, but none captures the whole picture.
3. Theories describe different aspects of intelligence: Like blind men describing an elephant, each theory sees only part of the whole.
4. Intelligence is a hypothetical construct: It is not a tangible “thing,” but an interaction between person, task, and context. Sternberg sees this explanation as the most plausible.

Intelligence as an interaction between Person, Task and Situation

Sternberg sees intelligence not as a single property that resides in a person's head, but as an abstract representation of how effectively a person adapts to various tasks and situations in his or her environment. In this view, intelligence represents a predicted sequence of successes a person will have in the person × task × situation interactions necessary for adaptation to the environment. Thus, IQ tests do not measure a fixed internal quantity, but predict how well a person will perform in adaptive interactions.

► A theory is incomplete if it places intelligence exclusively within the person, without taking into account the interaction between the person, the task, and the situation.

The role of context in displaying intelligence

How intelligence is expressed is strongly influenced by one’s attitudes and choices, such as the desire to act intelligently or not. Different tasks and situations affect how intelligence is expressed, causing abilities to vary depending on the context. Therefore, the definition of intelligence should be expanded to include creative, practical, and wisdom-based abilities, as well as meta-intelligence. Meta-intelligence is the ability to know what type of thinking to apply in different situations. Individual differences in intellectual abilities are also shaped by the tasks and situations people face.

► The search for the Holy Grail of intelligence, supposed to be something locked away within a person, has failed because no such Grail exists. Instead, our energy would be better spent investigating how intelligence is deployed, since intelligence depends on the person, task, and situation.

The Ethics of Intelligence: Use for Good or Evil

The ability to adapt can lead to destructive outcomes. This is seen in dictators who were widely considered unintelligent but who increased their power through manipulation. Intelligent behavior depends on what is considered adaptive within the context of power and social structures. Dictators such as Hitler, Stalin, and Mao and modern figures such as Donald Trump and JD Vance use intelligence for personal and destructive purposes. Intelligence can be used for both good and evil, and it is important to consider how we use intelligence to improve the world rather than destroy it.

► The question is not only who is intelligent, but especially how that intelligence is used to create a better future or to cause harm.

Relationship with the progress-focused approach

There is a relationship between Robert Sternberg's ideas and the three theoretical pillars of the progress-focused approach: 1) the mindset theory, 2) the self-determination theory and 3) the science of wisdom.

• Mindset theory: Carol Dweck's mindset theory emphasizes that intelligence is not static, but can be developed through effort, persistence, effective strategies, and support. Sternberg's view that intelligence is dynamic and context-dependent is consistent with this. Both approaches emphasize that intelligence is not fixed, but can be influenced by one's attitudes and interactions with the environment.
• Self-Determination Theory: Deci and Ryan's self-determination theory posits that people are optimally motivated when their basic psychological needs for autonomy, competence, and relatedness are met. Sternberg's emphasis on the role of attitudes and choices in the expression of intelligence reflects the importance of autonomous motivation. When individuals feel autonomous, competent, and related, they are more willing and able to use their intelligence effectively.
• Science of wisdom: The science of wisdom focuses on morally grounded excellence in social-cognitive processing. Sternberg integrates wisdom into his concept of intelligence by emphasizing that intelligence is not only about cognitive abilities, but also about their ethical use for achieving a common good. This is consistent with the characteristics of wisdom, such as moral grounding and excellence in social-cognitive processing.

► By integrating these insights, we can approach intelligence as a developable and context-dependent capacity that, when supported by the right mindset, motivation and wisdom, can contribute to personal growth and societal improvement.