Most of the terms given below are explained in the text, but it is hoped that this alphabetical list with brief definitions will prove helpful. It is a difficult task to make the definitions scientific and at the same time brief, simple, and clear.

Abnormal.

Having mental or physical characteristics widely different from those commonly found in ordinary people.

Acquired nature.

Those aspects of habit, skill, knowledge, ideas, and ideals that come from experience and are due to experience.

Action.

Muscular contractions usually producing motion of the body or of some part of the body.

Adaptation.

Adjustment to one’s surroundings.

Adaptive.

Readily changing one’s responses and acquiring such new responses as enable one to meet successfully new situations; also having tendencies or characteristics which enable one to be readily adjustable.

After-images.

Images that follow immediately after stimulation of a sense organ, and resulting from this stimulation.

Association.

Binding together ideas through experiencing them together.

Attention.

Relative clearness of perceptions and ideas.

Attitude.

The tendency toward a particular type of response in action or a particular idea or association in thought.

Bond.

The connection established in the nervous system which makes a certain response follow a certain stimulus or a certain idea follow another idea or perception.

Capacity.

The possibility of learning, achieving, etc.

Color blindness.

Inability to experience certain colors, usually red and green.

Complementary color.

Complementary colors are those which, mixed in the right proportion, produce gray.

Congenital.

Inborn.

Connection.

The nerve-path through which a stimulus produces a response or through which one idea produces or evokes another.

Conscious.

Having consciousness, or accompanying consciousness or producing consciousness.

Consciousness.

The mental states—perceptions, ideas, feelings—which one has at any moment.

Low level of consciousness.

Conscious processes not so clear as others existing at the same time.

High level of consciousness.

Conscious processes that are clear as compared to others existing at the same time.

Contrast.

The enhancing or strengthening of a sensation by another of opposite quality.

Correlation.

The relation that exists between two functions, characteristics, or attributes that enables us, finding one, to predict the presence of the other.

Development.

The appearance, or growth, or strengthening of a characteristic.

Emotion.

The pleasure-pain aspect of experience plus sensations from characteristic bodily reactions.

Environment.

The objects and forces about us which affect us through our senses.

Environmental instincts.

Instincts which have originated, at least in part, from the periodic changes in man’s environment.

Eugenics.

The science of race improvement through selective breeding or proper marriages or in some cases through the prevention of marriage.

Experience.

What we learn of the world through sensation and perception.

Fatigue.

Inability to work produced by work and which only rest will cure.

Feeble-minded.

Having important mental traits only poorly developed or not at all.

Feeling.

The pleasure-pain aspect of experience or of ideational states.

Function.

The use of a thing or process, also any mental process or combination of processes considered as a unit.

Genetic.

Having reference to origin and development.

Habits.

Definite responses to definite stimuli depending upon bonds established by use after birth.

Heredity.

Transmission of characteristics from parent to offspring.

Human nature.

The characteristics and tendencies which we have as human beings, with particular reference to mind and action.

Ideals.

Definite tendencies to act in definite ways. Ideas of definite types of action with tendency toward the actions; ideas of definite conditions, forms, and states together with a desire to experience or possess them.

Ideas.

Revived perceptions.

Images.

Revived sensations, simpler than ideas.

Imitation.

Acting as we see others act.

Impulse.

Tendency to action.

Individualistic instincts.

Those instincts which more immediately serve individual survival.

Individual differences.

The mental and physical differences between people.

Inherited nature.

Those aspects of one’s nature due directly to heredity.

Instincts.

Definite responses produced by definite stimuli through hereditary connections in the nervous system.

Intellectual habits.

Definite fixed connections between ideas; definite ways of meeting typical thought situations.

Intensity.

The amount or strength of a sensation or image, how far it is from nothing.

Interest.

The aspect given to experience or thinking by attention and pleasure.

Learning.

Establishing new bonds or connections in the nervous system; acquiring habits; gaining knowledge.

Memory.

The retention of experience; retained and reproduced experience.

Mental set.

Mental attitude or disposition.

Mind.

The sum total of one’s conscious states from birth to death.

Nerve-path.

The route traversed by a nerve-stimulus or excitation.

Original nature.

All those aspects of mind and body directly inherited.

Perceive.

To be aware of a thing through sensation.

Perception.

Awareness of a thing through sensation or a fusion of sensations.

Plasticity.

Modifiability, making easy the formation of new bonds or nerve-connections.

Presupposition.

A theory or hypothesis on which an argument or a system of arguments or principles is based.

Primary.

First, original, elementary, perceptive experience as distinguished from ideational experience.

Reaction.

The action immediately following a stimulus and produced by it.

Reasoning.

Thinking to a purpose; trying to meet a new situation.

Reflex.

A very simple act brought about by a stimulus through an hereditary nerve-path.

Response.

The act following a stimulus and produced by it.

Retention.

Memory; modification of the nervous system making possible the revival of experience.

Science.

Knowledge classified and systematized.

Sensation.

Primary experience; consciousness directly due to the stimulation of a sense organ.

Sense.

To sense is to have sensation, to perceive. A sense is a sense organ or the ability to have sensation through a sense organ.

Sense organ.

A modified nerve-end with accompanying apparatus or mechanism making possible a certain form of stimulation.

Sensitive.

Capable of giving rise to sensation, or transmitting a nerve-current.

Sensitivity.

Property of, or capacity for being sensitive.

Sensory.

Relating to a sense organ or to sensation.

Situation.

The total environmental influences of any one moment.

Socialistic instincts.

The instincts related more directly to the survival of a social group.

Stimulation.

The setting up of a nerve process in a sense organ or in a nerve tract.

Stimulus.

That which produces stimulation.

Subnormal.

Having characteristics considerably below the normal.

Tendency.

Probability of a nerve-current taking a certain direction due to nerve-organization.

Thinking.

The passing of images and ideas.

Thought.

Thinking; an idea or group of ideas.

Training.

Establishing nerve connection or bonds.

Vividness.

Clearness of sensations, perceptions, images, and ideas.