In mammalian species, the organ in the uterus containing blood vessels that unites the fetus and mother, providing the fetus with oxygen and nutrients from maternal circulation while also removing waste products. Made by trophoblastic tissue and extra embryonic mesoderm. See Amnion (or amniotic sac), Chorion, Dizygotic twins, Mesoderm, Monozygotic twins, Nicotine, Ontogenetic adaptation, Pulsatility index (PI)
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Pitch
A property of sound that varies with variation in the frequency of vibration. It is also the ability to identify any pitch heard or produce any pitch referred to by name, which is referred to as perfect pitch. Thus, the term is used for both a stimulus parameter (i.e., synonymous with frequency), and as an …
Pincer grasp (or grip)
Grasping(small) objects between thumb and index finger. By 8-9 months, infantsdemonstrate an inferior pincer grasp (thumb adducted so as to secure objectagainst extended index finger) and by 10-12 months the superior pincer grasp(complete opposition of thumb pad and index finger pad). The latter tends toco-occur with the first age of appearance of pointing with the …
Pineal gland
Sometimes referred to as the ‘third eye’, it haslong been associated with the claim made by René Descartes (1596-1650) that the gland was the‘seat of the soul’. It is a smallendocrine gland located in the epithalamus whose primary function is to producemelatonin and serotonin (a precursor of melatonin). The pineal gland is richly innervated byadrenergic …
Piaget’s stage theory
According to Piaget’s theory, development occurs through a series of major periods or stages that contain their own sub-stages and in which psychological activity differs qualitatively from one period to the next. The main principle that makes the stage progression necessary and non-arbitrary is that the major achievement of one period sets the necessary starting …
Pictorial depth cues
Any visual Information in two dimensions about relative distance that can be depicted in a picture or photograph and from which three-dimensional inferences can be drawn. This form of depth perception derives from monocular cues. Many studies have been carried out on when infants first respond to pictorial depth cues based on visual preference (with …
Pia mater
In short, it is the innermost layer of the meninges, a delicate fibrous tissue entirely covering the central nervous system. The other two layers are the dura mater (outer layer) and the arachnoid mater (inner layer). When it becomes infected or irritated, the consequence is meningitis. Cerebrospinal fluid fills the subarachnoid space overlying the pia mater, …
Phylogeny
The historical paths taken by evolving groups of animals and plants over geological time. Often used interchangeably with biological evolution, the two terms need to be distinguished from each other. The distinction is between providing a descriptive evolutionary history of a species (phylogeny) and attempting to explain the processes (phyletic gradualism or punctuated equilibrium) and …
Physical knowledge
Knowledge about the physical properties of objects. Often used interchangeably with biological knowledge, the two terms should be distinguished from each other. See Balance scale task, Biological knowledge, Core concepts, Data-driven processes, Intuitive theory of something
Phylogenetic skills
Those abilities in infants designated by Myrtle McGraw (1899-1988) to have a long evolutionary history (e.g., locomotion) and which are therefore much less susceptible to experience than ontogenetic skills. Attempting the distinguish between the two was rather unfortunate as it assumes that evolutionary influences have less of an effect on the development of ontogenetic skills, when in …