What do "track" and "screen" mean in this context?

Question

The first study showed infants a toy car that moved down an inclined track, disappeared behind a screen, and then reemerged at the other end, still on the track. The researchers created a "possible event" where a toy mouse was placed behind the tracks but was hidden by the screen as the car rolled by. Then, researchers created an "impossible event." In this situation, the toy mouse was placed on the tracks but was secretly removed after the screen was lowered so that the car seemed to go through the mouse.

Source: http://en.wikipedia.org/wiki/Object_permanence#Contradicting_evidence

In addition to those words, can someone explain the bolded parts?

Answer 1

Track here means "(miniature|toy) roadway|tramway|railway". Screen is something that obstructs the view, like a small panel that can be placed between the viewer and an object.

This online dictionary has the definitions above: http://www.merriam-webster.com/

EDIT: The infant was shown a car moving down an inclined track, then passing out of view behind a screen, and then emerging from behind the screen.

Then a toy mouse was placed on the track in the car's path. The mouse was like a pedestrian standing in the roadway, as it were. The mouse was apparently as big as the car. The two were not "to scale".

Then a screen was placed in front of the toy mouse, obstructing the infant's view of the mouse. When the infant could no longer see the mouse, it was removed from the track.

Then the car was allowed to roll down the track, behind the screen, and then emerge again from behind the screen. The discerning infant might think the car had driven "through the mouse" in order to emerge from behind the screen.