Review of Sodastream and the psychology of the taste test

The review of Sodastream

A few days ago I was kidnapped by my bride of 26 years and forced to spend 3 days in Ashland, Oregon celebrating our anniversary. Ashland is a beautiful village best known for the Oregon Shakespeare Festival. The leaves were turning the flaming colors of autumn, and the temperatures were unseasonably warm.

Sodastream Revolution Deluxe Home Soda Maker


As if this wasn’t enough, my wife, Geri, got me a Sodastream home soda maker. This innovative device allows you to make sodas of all flavors at home. You even get to pick the amount of carbonation you fancy. The company makes loads of flavor choices, or you can easily squeeze your own fruit juices into the effervescent water.

Geri and I had lots of fun trying different combinations of flavors and amounts of carbonation (the machine came with 12 sample packs each making 1 quart). We were not scientific about how we got to our taste conclusions, and that was OK because we were playing with a new soda making machine, not doing drug trials.

But, what if we truly wanted to test the taste preferences of soda drinking consumers? If so, we would need to do a “blind test”.

A blind test

A blind test is when the test subject doesn’t know what brand they are tasting. If you were to test preferences on say, Coke or Pepsi, the test taster may already have a preference for one or the other before you invited them to participate. The fact that we have preferences before an experiment is called, bias. Part of setting up a taste test is to lower the amount of bias.

So, if we are going to test Coke versus Pepsi, we would place the drinks in unmarked glasses and ask the test subject to try both and tell us their opinion. This however lets lots of other forms of bias wiggle into our simple test.

What if the first thing we taste or the last thing we taste influences how we judge the drinks in our experiment? In fact we know, from other experiments, that this does influence a subject's preferences, so we have to randomize which soda is tested first or last.

At one point in our own home test, Geri tasted one sample and said, “It’s not bad, but it will be too sweet for you.” Wow, this is a clear example of research contamination. Her statement would most likely influence how I would judge that soda sample, even if I really tried not to be influenced by her words.

Another form of research contamination is when the person conducting the experiment is aware of the samples or the goal of the experiment. This is called experimental bias.

Double blind

To reduce bias in an experiment, it is best to have both the subject and the person conducting the trial "blinded", unaware, to the facts of the taste test.

Even if the person conducting the trial honestly tries to keep her opinions to herself, bias will most-likely sneak in. She many not say anything, but just the way she hands the glass to the tester, the minute social subtleties, will give clues to the subject. We humans pick up on social cues even when we are not consciously aware of them.

Blinding in research is important but very hard to do. For example, the color or temperature of the soda will influence the test subject. The psychological bias of what we expect from a soda will influence how we taste it.  Manufacturers know this so soda is colorized to elicit the correct feeling from the drinker, even though the coloring in the drink does not influence the taste of the drink. But it does influence your perceived taste of the drink.

Perceived value influences taste

Research has shown that wine tastes better in a expense glass versus a cheap glass. But the glass does not affect the taste of the wine. It is just that the drinker feels differently about the wine… and that feeling affects the taste of the wine.

Ben Hayden, Ph.D - TEDTalk Rochester, NY


Ben Hayden, Ph.D., an Assistant Professor of Brain and Cognitive Sciences at the University of Rochester, has conducted lots of tests on the psychology of consumer preference. He wrote in Psychology Today:

Wine is a multi-billion dollar industry part of the modern world. There are stores devoted just to selling wine, magazines devoted to it, wineries are a major tourist destination, and so on. And yet, weirdly, we know that much of this is a psychological artifact.

We are quite bad at tasting the differences between different wines. Even experts are easily fooled. You put a misleading label on a bottle of wine and the experts’ opinions can change dramatically. You can even warm up white wine and color it red (with food coloring) and many judges will think it is a red wine.

This is not just true for wine. Most people can’t taste the difference between Coke and Pepsi (even though most people think they can – I’ve done the experiments).

All this being said

Geri and I are enjoying the Sodastream home soda maker. I like the diet cola and the diet ginger ale, while Geri seems to be enjoying an ongoing taste test. Isn’t life wonderful when you get to drink the soda flavor of your choice?

The moral of the story

When it comes to being human, it is often forgotten that we don’t know what we don’t know. We people types are influenced by psychological bias. Our job is to watch for our own psychological biases in our life. So hopefully, when we notice this bias, we can logically make better choices.