The Shape of Randomness

If I give a task to mark 100 random dots on a paper, which of the following two patterns do you likely to come up with?

Studies have found that there is a tendency for people to identify uniform patterns when asked about randomness. In the above picture, the one on the right was generated by a random program.

Now another: Two students were asked to toss coins 20 times and record. Following is what they came up with. If one of them made up his experiment, who could that be?

1) THTTHTTHHTTTTTHTTHTH
2) THHTTHTHTTHHTHTTHTH

Clusters in randomness

It is difficult for most people to imagine that long clusters of Ts in the first case come randomly. After all, shouldn’t the equal probabilities of occurrence of heads and tails suggest an even distribution, like in the second case?