Does Tryptophan in turkey cause sleepiness?

Many people believe tryptophan in turkey may cause sleepiness or tiredness on the thanksgiving day.  But that is not the case.

Turkey contains high amounts of tryptophan, but the amount of tryptophan in turkey is typical of most poultry, according to wikipedia.  If turkey induces sleepiness, it must be something else. 

Tryptophan, often misspelled as triptophan, is an essential amino acid in human diet that is needed for biosynthesis of proteins. Humans can't make tryptophan and it must come from foods.

Tryptophan is involved in synthesis of serotonin ( neurotransmitter), niacin (a vitamin), and auxin (a phytohormone).

So tryptophan is an important amino acid. Foods found high in tryptophan include chocolate, oats, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, sunflower seeds, pumpkin seeds, spirulina, and peanuts.

Tryptophan is also available as a dietary supplement. It is believed that the dietary supplements may serve as a safe and effective sleep aid because it leads to the production of melatonin - a sleep inducing hormone.