How might happiness be used as a dependent and independent variable in a study? Give examples for each.
If happiness is your dependent variable, it means that you are measuring your subject group’s happiness based on the alteration of a different variable. For instance, you might be looking at the effects of looking at silly cat pictures on happiness, or whether divorcees report more or less happiness than married people.
If happiness were to be your independent variable, it would mean that you are looking at the effect of happiness on some other measurable attribute--for example, the effect of happiness on creative productivity among artists, or the effect of happiness on lifespan among women.
If happiness is your dependent variable you are measuring the effect of another variable on happiness, while if happiness is your independent variable, you are measuring happiness’s effect on something else.
An important consideration is that whether happiness is your independent or dependent variable, you will need to find some way of measuring happiness, a difficult state to quantify. You could consider using some type of self-reported survey or interview to measure happiness, or using the subjective reports of others, or even looking at the brain states of your subjects!
If you are asking why psychologists would view happiness as something people have control over, the answer is obvious. Given a choice, most people would voluntarily choose to be happy over being sad. I say most people, because there are always extenuating circumstances that are clearly out of a persons control, such as mental instability or physical disease. Given good health and stable mental health, everyone wants to be happy, not sad. As people grow and mature from children to adulthood, one of the driving motivators is to figure out what makes you happy. For example, I have three sons, age 25, 21, and 15. The oldest sons idea of happiness is going to his favorite rock concert, while son number twos idea is working out in a gymn. Most people, at some point, figure out what they like to do and center their lives around that. It should also be pointed out that our lives are not works of perfection. There will be days where we experience events that make us sad. But this is not the norm; the sun will come up tomorrow, there will be another chance, and we need not fixate on the negatives in life that inevitably show up from time to time.
An independent variable is a variable that we believe contributes to, causes, or explains something else. So to use happiness as an independent variable, we might look at whether happier people donate more to charity, or if being happy is linked to lower rates of mental illness.
A dependent variable is a variable that we believe is caused or explained by something else. So to use happiness as a dependent variable, we might look at whether increased income leads to increased happiness, or whether more educated people are happier.
We could also use happiness as both independent and dependent variables: For example, we might want to know if being happy this year is closely correlated with being happy five years from now, and thus use this year's happiness as an independent variable and later happiness as a dependent variable.
Of course, for any particular study, we'd have to ask how happiness is being measured; various methods involving surveys or even brain scans can be used, but each comes with drawbacks.
Happiness, as many people say, is only a state of mind. We also know that happiness eludes us when we try hard to pursue it. A lot of research has shown that it is better not to pursue happiness but to make choices in our day-to-day lives that bring us happiness. By engaging in an activity such as doing embroidery or baking or playing badminton or reading, if one can experience the flow, then one generally tends to be happy.
Let us take the example of a group of people seated in a restaurant and deciding what food to order. Imagine that each one of them ordered an item from the menu that made him/her happy without giving thought to its price, popularity, number of calories etc. Here we have a case where happiness is being used as a dependent variable.
Let us look at another example. We have a college graduate looking for a job. The only criterion for him is the pay packet. Nothing else matters to him - will the job be interesting, will he be happy doing it, what are his future growth prospects - he is not interested in any of these except the pay. Needless to say, he will not be happy doing this kind of job after a while. So here we have a case where happiness is being used as an independent variable.