Psychology Dictionary -- I


In Psychoanalytical theory, the part of the personality which contains our primitive impulses such as sex, anger, and hunger.

Ideal Self

Humanistic term representing the characteristics, behaviors, emotions, and thoughts to which a person aspires.


Misperception of reality (e.g., the illusion of a lake in the middle of a desert).


Utilizing the mind to create a mental representation of a sensory experience.

Inappropriate Affect

Expressing contradictory behavior when describing or experiencing an emotion (e.g., smiling when discussing something sad; laughing when talking about the death of a loved one).

Independent Samples

Sample data that is independent or not related to each other.

Independent Variable

The variable in an experiment that is manipulated or compared.

Inductive Reasoning

Decision making process in which ideas are processed from the specific to the general.

Industrial/Organizational Psychology

The area or specialty in psychology focused on the application of psychological principles in the work force.

Inferential Statistics

The branch of statistics that focuses on describing in numerical format what might be happening or what might happen (estimation) in the future (probability). Inferential statistics required the testing of only a sample of the population. (Example: 100 students rather than all students).


Substances such as spray paint, freon, and glue that produce an intoxicating effect when inhaled.


Occurring without learning, inborn.


A legal term representing the inability to know right from wrong or the inability to understand the consequences of one’s actions.


The understanding of a relationship between current thoughts, feelings, and/or behaviors and where these originated or how they are maintained.


A behavior we are born with and therefore does not need to be learned.


The degree to which one can adapt to one’s environment.

Intelligence Quotient [IQ]

The scores achieved on psychological tests aimed at quantifying intellectual ability.

Interaction Effects

When the effect of one variable on another is contingent on a third variable, this contingency is called an interaction effect.

Internal Consistency

An estimate of how reliable a test is when items on the test are compared to each other. See split-half and odd-even reliability.

Internal Locus of Control

The belief that an individual has more control over life circumstances than the environment does.

Internal Validity

A measure of the trustworthiness of a sample of data. Internal validity looks at the subject, testing, and environment in which the data collection took place.

Interquartile Range

The difference between the scores (or estimated scores) at the 75th percentile and the 25th percentile. Used more than the range because it eliminates extreme scores.

Interval Estimation

Estimating the population statistic based on a range around a sample statistic.

Interval Scale

Any scale of measurement possessing magnitude and equal intervals, but not an absolute zero.


A subjective personality and mental health assessment typically consisting of questions and answers.

Intrinsic Motivation

The motivation or desire to do something based on the enjoyment of the behavior itself rather than relying on or requiring external reinforcement.


The process of examining one’s own consciousness.


The tendency to focus energy inward resulting in decreased social interaction.