“I believe that the brain has evolved over millions of years to be responsive to different kinds of content in the world. Language content, musical content, spatial content, numerical content, etc.”
-- Howard Gardner

Gardner (2006) defines intelligence as "a computational capacity -a capacity to process certain kind of information- that originates in human biology and human psychology" (p. 6). It "entails the ability to solve problems, or fashion products, that are of consequence in a particular cultural setting or community" (Gardner 2006, P. 6). The intelligence types represent problem solving skills universal to the human species (Gardner 2006). His qualitative way of measuring intelligence is a response to the classic quantitative meassuring methods (psychometric) where a numberic value is assigned to questions to meassure intelligence (like IQ tests).

In 1999 he wrote the book "Intelligence reframed" in which he considers new candidate intelligences including naturalistic, existential, spiritual and moral. There has been some controversy about these last types, which is why only the first seven types are considered by many other authors and educators.

The decision to not add spiritual intelligence to the theory is first due to it's religious nature. Second, he didn't believe that an intelligence should be limited to a phenomenological experience. When talking about the moral intelligence, Gardner establishes morals as "a subspecies of a cultural value system. " For him adhering to moral values is a result of a personal decision and not an exercise of intelligence (Gardner 2000). In Intelligence Reframed, he concludes that neither he nor anyone else have succesfully "captured the essence of the moral domains as an instance of human intelligence" (Gardner 2000).
Types of intelligences
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Implications of the multiple intelligences theory in the education field.
Many studies exist on the effect of implementing the MI theory in the classroom. Gardner (2006) mentions the project SUMIT (Schools using multimple intelligence theory) in which the research team studied a set of 40 schools that have been using MI theory for at least three years. Improvement on standardized tests as well as in classroom performances by students with learning disabilities were found in 78% percent of those schools. Another area of improvement was student discipline. At least 5/8 of these results have been attributed to the implementation of the MI theory.
Studies like SUMIT, prove that we can improve learners' performance by implementing multiple intelligences theory in our lessons and classrooms. With MI, both teachers and students start to understand how they are intelligent. This way students can start managing their own learning and teachers can create opportunities to promote the development of different types of intelligences.
As mentioned before, human beings have the capacity for all types of intelligence. Therefore, educators shouldn't typecast students into one intellectual profile or another (Garner 2006). As educators we can't think that because a student has developed a certain type of intelligence, then they will or won't develop other types. The idea is to give opportunities and understanding for the students to express themselves in different ways and approach understanding and problems from different angles.