Your second critique about how subjects might have done more poorly because they were distracted due to a valued item being not in their possession – hmmm…I don’t know if I buy it. I mean – the lucky charm wasn’t lost (it was just in the other room), so I don’t think any significant distraction would take place. Interesting comment though!

The second study – pressing the thumbs – why not have a third condition in which the thumbs were pressed, but the participants were not told of this. Perhaps not explicitly necessary to the study (assuming a scientific audience who knows superstitions themselves have no power), but worth emphasizing the point that it’s the participants’ beliefs that drive the improvement in performance.

The third and fourth studies – the lucky charm kept away – I’m not convinced at all that the participants whose charms were kept away weren’t simply distracted by having a valued item out of their control. Why not ask half the students to bring something of value, stating that it should not be a lucky charm, or ask all the students to bring two items: a lucky charm and a non-lucky item of sentimental value. Including conditions where only the non-lucky item was kept beyond their control would tell whether or not it was the loss of the lucky item or simply being distracted with a lost item that caused participants to perform more poorly.

Interesting study regardless, and I look forward to looking it over fully later. Off to work for me!