Reflexes

For this research project, you will need the permission of parents of a young infant (one to four months old) and an older infant (six to twelve months old) to examine their infant's reflex repertoire. In order to test the two infants, you will need to clear this project through the human subjects review board at your school and get a signed informed consent form from the baby's parents. You may work in groups of 2 to 4 to make it easier to locate and gain access to the appropriately aged infants. Be certain to indicate age by months because your results will vary if you use a 2-month vs. a 4-month baby or a 6-month vs. an 11-month baby.

For each infant, perform the stimulation necessary to elicit the reflexive behavior. Note which of the reflexes are present (P) or absent (A) for each infant. You may mark these responses in the chart below. After performing the demonstration with each infant, answer the questions.

Infant 1 Infant 2

Reflex Simulation and reflex Sex__Age_ Sex_ Age_

Placing Backs of infant’s feet are P/A P/A

drawn against a flat

surface’s edge:

Baby withdraws foot

Hold baby under arms P/A P/A

Walking with bare feet touching

flat surface: Baby makes

steplike motions that

appear like coordinated

walking

Stroke palm of infant’s

hand: Baby makes strong P/A P/A

Darwinian fist; if both fists are

(grasping) closed around a stick, the

Infant could be raised to

standing position.

Baby is laid down on

back: Infant turns head to

one side and extends arms

Tonic and legs on preferred side P/A P/A

neck and flexes opposite limbs

Make a sudden, loud

Moro noise near infant:

(startle) Infant extends legs, arms, P/A P/A

and fingers, arches back,

and draws back head.

Stroke sole of baby’s foot:

Babinski Infant’s toes fan out and P/A P/A

foot twists in.

Stroke baby’s cheek with

Rooting one’s finger:

Baby’s head turns, mouth P/A P/A

opens, and sucking

movements begin.

Questions

1. How many of the reflexive behaviors were exhibited by the younger infants? By the older infants?

2. Which reflexes dropped out early?

3. What responses seem to replace each of the reflexive behaviors in the older infants?

4. What might be the adaptive value of each reflex in the newborn's repertoire?

Chapter 6