How do you decide when to buy something in the store vs. online?

The answer is somewhat complicated, a blend of the subjective and the scientific.

"I think that the more familiar and predictable a product, the safer you are buying it from a reputable online retailer," said Philip Graves, a consumer psychologist and author of "Consumer.ology: The Truth About Consumers and the Psychology of Shopping."

For example, Graves said, if he knew which model of well-known watch he wanted to buy, he would purchase it online due to brand consistency. But if he hadn't already decided on a purchase, he would go to a store.

Things can be purchased without ever seeing them in person, such as electronics — if you read the reviews. But the reviews can tell you only how a product works, not how much you will like it.

"The more subjective the experience you will have from a product, the more likely it is that you would benefit from buying it in a store," Graves said.

"I once bought a bed online, based on the description. That was a huge mistake. I don't think anyone can adequately describe to someone else how they will feel lying on a particular bed."

Shopping, however, comes down to much more than making the purchase.

When shopping online, the amount of time spent deliberating over a purchase increases because consumers have access to more information. For some, this can be overwhelming. So if this is the case (and if time is a factor), then going to a store may be a better choice, Graves said.

But for others, a store visit may make them buy more items than anticipated.

"In a store, you have access to a wider variety of ways to influence people: Music, scents, lighting, fixtures and sales assistants are all sources of influence that make us more likely to buy," Graves said.

Researchers have noticed that many people do both online and in-store shopping for some purchases.

"If we interview customers walking out of a store, a remarkable percentage of them have done some pre-shopping online," said Paco Underhill, author of "What Women Want: The Science of Female Shopping." "For many of us, that's viewed as being smart."

These hybrid shoppers are researching the item and checking price, size and details before going into the store to make sure they want to buy it, Underhill said. Or they're shopping the other way around: looking at the item in the store before going online to see if they can find a better price.

More than just a purchase

Still, a large part of shopping isn't actually making the purchase. It's the thrill of shopping, and this can be had whether online or in person, he said.

"That's something that's moved from going to the mall to going online," Underhill said.

There are people who log onto eBay or Gilt.com "who will spend hours and hours and hours and get nothing," he said. "They said that the reason why they're there is because they're tired of reruns of 'Friends.' "

In a 2013 study of online vs. in-store shopping by WD Partners, a strategy design and architectural firm based in Ohio, many shoppers said the experience of shopping in a store can't be replaced by its online counterpart.

Seventy-nine percent of shoppers reported instant gratification as a top factor in influencing their decision to shop in the stores. The study found 75 percent of consumers like to touch the items and experience a human connection.

"Shopping in the stores is much more emotional — you're with your friends, you're listening to music; it's much more human," said Lee Peterson, executive vice president of creative services for WD Partners.

Age was a factor in who favored the experience of shopping in-store, Peterson said.

"The younger responders liked the online reviews, the online endless aisle, the ability to get anything you want."