BABINSKI REFLEX--the tendency for an infant to fan his toes when the sole of his foot is gently stroked.

CEPHALOCAUDAL--progressive development from head to trunk.

CHROMOSOMES--carriers of hereditary material.

CRITICAL PERIOD--a period of time during which an organism is most susceptible to the acquisition of certain responses.

CROSS-CULTURAL STUDY--a special type of cross-sectional study in which one compares groups from different societies.

CROSS-SECTIONAL STUDY--one in which comparisons are made between different groups of differing ages or backgrounds.

DARWINIAN REFLEX--the tendency for an infant to grasp hard when anything touches his palm.

DNA (DEOXYRIBONUCLEIC ACID)--a large, complex protein molecule that is the basic hereditary material.

DOMINANT GENE--a gene whose hereditary characteristics are always expressed and are therefore evident as a trait in the individual. Seerecessive gene.

FRATERNAL TWINS--twins developed from two separate fertilized eggs and hence are twins who are no more similar genetically than ordinary siblings.

GENE--a determiner of a trait. A segment of a DNA molecule.

GUILT--the realization that one has violated legal, moral, ethical, or religious laws; a self-initiated, but involuntary, form of punishment.

IDENTICAL TWINS--twins that develop from a single egg, hence they have identical heredities.


IMPRINTING-- a special type of learning that is species-specific and is characterized by the very rapid development of a response to a stimulus at some critical period of maturation.

INSTINCTIVE complex, unlearned pattern of behavior that persists beyond the duration of the original stimulus.

LONGITUDINAL STUDY--one in which the same individuals are followed through various stages in their development.

MORO REFLEX--the startle reflex in infants, initiated by a sharp noise and characterized by bringing the legs and arms forward as if to embrace someone or something.

OEDIPAL PERIOD--that period of life occurring around the age of five,characterized by the attachment of a boy for his mother. According to psychoanalytic theory, the critical period for sexual development.

PROXIMODISTAL--progressive development from central to peripheral parts.

RECESSIVE GENE--a gene whose hereditary characteristics are not expressed when it is paired with a dominant gene.

REFLEX--an unlearned behavioral pattern largely under the control of a specific stimulus.

SEX ROLES--a full range of attitudes and social roles that a culture or society expects and considers to be appropriate for one sex or the other.

STAGE--a period or step in a process of development.

STAGE THEORY--the view that an individual must reach a certain state of readiness before he is able to benefit from reaming experience(s).

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