Two-Month-Old Infants Show a Decrease in Heart Rate When Placed

question 110

Multiple Choice

Two-month-old infants show a decrease in heart rate when placed on the deep side of a visual cliff apparatus, but no change in heart rate when placed on the shallow side.What does this difference in heart rate indicate about the infant's perception of depth?

• A)They cannot yet detect the difference between the two sides.
• B)They can detect the difference between the two sides and are afraid of the deep side.
• C)They can detect the difference between the two sides, but they do not yet fear the deep side.
• D)They cannot detect the difference between the two sides but are more interested in the shallow side.

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Definitions:

Early Gastrula

A stage in embryonic development following blastula, characterized by the formation of the primitive gut and the establishment of germ layers.

Late Blastula

A stage in embryonic development characterized by a spherical layer of cells (the blastoderm) surrounding a fluid-filled cavity (the blastocoel).

Morula

A solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.

Primitive Streak

Dynamic, constantly changing structure that forms at the midline of the blastodisc in birds, mammals, and some other vertebrates. It is active in gastrulation as cells migrate to a narrow furrow at its center, the primitive groove, and sink into the interior of the embryo. The anterior end of the primitive streak is Hensen’s node.