Howard Gardner was asked for his views on stupidity. He decided to begin by describing various connotations of the word ‘intelligent’ and then distinguished among three forms of stupidity. The following are his thoughts on the matter.
I begin with the recognition that intelligence can be defined in three separate ways:
1) Intelligence as a property of all animals.
Unless grossly impaired, all human beings have certain problem-solving capacities—as do monkeys, dogs, mice, and even invertebrates. This was the sense of intelligence as it was studied by Jean Piaget in the middle of the 20th century. (He wrote many books about human intelligence).
2) Intelligence as individual difference.
On any dimension, some human beings will be 'smarter' than others. This is the sense of intelligence that was first studied systematically by Alfred Binet over a century ago, when he created the first intelligence (or IQ) tests.
This is the sense of intelligence which I have challenged in my own research and writing. Whereas Binet (and, for that matter, Piaget) thought that they were investigating all of intelligence, I believe that they were largely investigating only two forms of intelligence—linguistic and logical-mathematical intelligence. My research has indicated that human beings have several more forms of intelligence, including musical intelligence, bodily intelligence, interpersonal intelligence, intrapersonal intelligence, spatial intelligence, the emotional intelligence studied by Daniel Goleman, etc. An individual's' strength in one form of intelligence—say, musical—has little predictive value with respect to other forms of intelligence—say linguistic or interpersonal intelligence.
3) Intelligence as the way that a person approaches problems or projects.
You can have two persons who have equally strong linguistic intelligence. They would perform equally well on a test of language comprehension or language production. But one person may constantly put his foot in his mouth, interrupt other people, say ill-considered things, write foolish letters or not write at all, choose never to learn a foreign language. The other person, with the same test performance data, may consider very carefully before he speaks, compose letters with great care, listen carefully to others, apply himself to the study of foreign languages.
So, given these three senses of intelligence, what can be said about stupidity?
With respect to the first sense, we cannot speak about stupidity of a particular person or a particular animal. What we can say is that birds are less smart than human beings in certain respects (e.g. less able to fix a broken machine) but smarter with respect to other capacities (for example, navigating their way through unfamiliar space).
With respect to the second sense, we no longer say that A is stupider than B. Instead we say that with respect to two forms of intelligence, A is smarter than B; with respect to three other forms of intelligence, B is smarter than A; and with respect to still other forms of intelligence, they are equally smart, or equally stupid.
With respect to the third sense, I would say that the first person is using his linguistic intelligence stupidly, while the second person is using his linguistic intelligence very cleverly, very smartly.
Summary: My analysis indicates that the word 'stupid' should not be used as a general characterization of a person, or of any other animal. We need to take into account which forms of intelligence are being discussed, and whether—given a certain degree of that intelligence—the person is using it cleverly or foolishly. I suspect that is the meaning of 'stupid' is the one that people usually have in mind.
But people may differ a lot in what they consider to be a smart use of a capacity. For example, to use an instance from the political scene in France today, some people may feel that Marine Le Pen is her linguistic intelligence cleverly, while others may feel that Marine Le Pen is using her linguistic intelligence stupidly. At issue here is the Value System of the person who employs the words 'smart' and 'stupid.'