The spinning woman illusion. To me, she always seem to spin clockwise: from right to left; and I have to make a conscious effort to look at the figure sideways to it reverse the direction.

The link comes courtesy a New Scientist article that proposes:

...when people make decisions, their pupils dilate, a subtle cue that could be used to predict a person's intentions, or even converse with people with locked-in syndrome.

A useful clue in negotiations. It would be good to have a monitoring device that tracks, Blade runner-style, your opposition's pupils.

The title of the article is slightly misleading, though. It mentions wide eyes rather than dilated pupils. The "wide eyes" effect is a sign of interest from another person, rather than decision-making activity. That's why men prefer women who listen to them with eyes wide open. Maybe the reporter for the story, Ewen Callaway, who is male, got carried away by his imagination. Or maybe it's a plot to grab our attention. Or maybe it's a little bit of both.

tags: psychology, effect, science, detection