Does sunshine dull the mind?

From Maria Popova’s wonderful Brainpickings:

In Drunk Tank Pink: And Other Unexpected Forces That Shape How We Think, Feel, and Behave (public library | IndieBound), NYU professor Adam Alter, who studies behavioral economics, marketing, and the psychology of decision-making, opens one particularly pause-giving section with this unambiguous proclamation:

Sunshine dulls the mind to risk and thoughtfulness.

He goes on to substantiate the heading with a curious, counterintuitive study conducted by social psychologists in Sydney, Australia. The researchers found that rather than invigorating the mind, good weather blunts our cognitive function.

The study was essentially an ambush memory test administered to a sample of shoppers exiting a small store: The scientists had placed ten trinkets on the store counter — various plastic toys, Matchbox cars, a piggy bank — and asked the shoppers to recall as many as possible upon leaving the store, as well as to identify the ten items among a list of twenty. The experiment was replicated on multiple days, at various times of day, over the course of two months.

The researchers found that shoppers were able to recall three times as many items on cloudy days than on sunny ones.

Does sunshine dull the mind?