What Factors Slow Down the Development of the Human Nervous System?

[Christophe]

I have some questions :
1> Would you please tell me what slows down the development of human nervous system ?
2> A situation: A very cute two year old baby was playing with his toys: I let him see a pink ball, ten times. Then let him see a blue ball. I tried to observe his actions and his eyes but found nothing the same as what my book says that his attention should be differernt from the previous times.
I tried again twenty times but indifferent either. How could I explain this situation ?
Thank you

-Christophe

 

[DocToxyn]

To your first question...it's a little broad, do you mean "slow down" as in simply delay development and then it catches up later or are you looking for a permanent alteration in function? Some things that come to mind are certain nutritional deficits leading to general developmental problems, i.e. hypothyroidism, any number of genetic syndromes, hypoxia during birth, toxicant exposure...

Your second question, I assume, is looking to test some aspect of visual recognition memory (?). I'm not sure how your book describes the performance of the task but the one I'm familiar with shows pictures to infants and measures their residence time on each image and small group of images is shown repetitively and then novel pictures are mixed in. The childs point of attention is captured by cameras and later analyzed for looking times which should be longer for the novel stimulus than the previously viewed (and recognized) images.

What the exact difference in fixation time typically is, I'm not sure and probably varies depending on how the task is performed, age of child, etc. Also it's not just a measure of how long they look, but how often as well and then a percentage of time looking at the novel stimulus is calculated. One paper I have using this task saw fixation to novelty for 67% percent of the looking time in the control group, not that far of from 50% and probably hard for you to judge just by eye. This might explain why you didn't observe the expected response, also if the room in which you did the test was distracting, other toys, people, etc, that may have clouded the results. The environments in which these test are performed are highly controlled and try their best to eliminate any potential distractions to the subject.