Why babies laugh

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Across
  1. 3. – Involving repeated observations of the same subjects over a long period.
  2. 5. – Contrary to what intuition or common sense would suggest.
  3. 6. – Referring to the process where nerve fibers are coated with myelin for faster signaling (used metaphorically for neurological maturity in the text).
  4. 8. – Not having serious purpose or value; trivial.
  5. 12. – A rhythmic sequence or flow of sounds.
  6. 13. – The act of assessing or evaluating a situation or event.
  7. 15. – Relating to mental processes of perception, memory, and reasoning.
  8. 16. – Attributing one's own human feelings to another being.
  9. 17. – Things that evoke a response in an organism (plural of stimulus).
  10. 19. – Done without conscious control.
  11. 20. – Relating to the brain's limbic system, involved in emotion and memory.
Down
  1. 1. – Gentle and kindly; not harmful.
  2. 2. – The emotional bond between an infant and caregiver.
  3. 4. – Able to recognize fine distinctions; selective.
  4. 7. – Lacking social interaction or context.
  5. 9. – Showing complex awareness or advanced processing ability.
  6. 10. – Recognition that something is acceptable or worthwhile.
  7. 11. – The state of being out of place or inconsistent with expectations.
  8. 14. – The quality of an action being performed on purpose or with a goal.
  9. 18. – The developmental path or progression over time.