I

Iconic memory

The brief persistence of a visual impression

Idiot savants

Individuals who demonstrate less than normal intelligence but are nevertheless endowed with far more than is usual of a particular ability

Implicit memory

Memory retrieved without conscious awareness

Indo-European

A language or group of languages spoken some thousands of years ago, from which many of the languages extant today derive (e.g.,English, French and Russian)

Inflectional suffix

A suffix that adds information to a word without changing its meaning or its grammatical category ( e.g.,the plural -s and the past tense -ed)

Innate knowledge

Knowledge one is assumed to have been born with

Insight

The grasping of the inner nature of a phenomenon, or the solution to a problem, by an intuitive process rather than, for example, by application of rules

Introspection

The practice of looking inside of one’s on experience, of attending to and becoming conscious of one’s own mental states

IQ 

Intelligence quotient, determined by dividing mental age ( as determined by a set of tests of mental function) by chronological age and multiplying by 100