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Independent and Dependent Variables: 25 Psychology Examples
The independent variable (IV) is what the researcher changes or compares. The dependent variable (DV) is what they measure to see if it changed. In "Does caffeine improve reaction time?", caffeine is the IV and reaction time is the DV. That's easy in a clean example. It gets harder in exam questions, correlational studies and real research designs, so below are 25 examples, a three-question test, and how to write the operational definitions instructors ask for.
The three-question test
- What did the researcher manipulate or group people by? That's the IV.
- What did they measure as the outcome? That's the DV.
- Can you put it in this sentence? "The effect of [IV] on [DV]." If it reads sensibly, you've got it right.
25 examples
Memory and cognition
| # | Study | IV | DV |
|---|---|---|---|
| 1 | Does background music affect recall of a word list? | Music vs silence | Number of words recalled |
| 2 | Does sleep deprivation slow reaction time? | Hours of sleep (4 vs 8) | Reaction time in milliseconds |
| 3 | Do students remember more after spaced or massed study? | Spaced vs massed practice | Test score out of 50 |
| 4 | Does handwriting notes improve recall compared with typing? | Handwriting vs typing | Score on a recall quiz |
| 5 | Does multitasking reduce reading comprehension? | Phone notifications on vs off | Comprehension score |
Social psychology
| # | Study | IV | DV |
|---|---|---|---|
| 6 | Does group size affect helping behaviour? | Number of bystanders (1, 3, 6) | Whether and how fast participant helps |
| 7 | Does a uniform increase obedience? | Researcher in uniform vs casual clothes | Percentage of participants who comply |
| 8 | Does anonymity increase online aggression? | Anonymous vs named accounts | Number of hostile comments |
| 9 | Do attractive people get lighter mock-trial sentences? | Defendant attractiveness (high vs low) | Recommended sentence in months |
| 10 | Does social media use affect self-esteem? | Time on social media (30 vs 120 minutes) | Rosenberg Self-Esteem Scale score |
Developmental and educational
| # | Study | IV | DV |
|---|---|---|---|
| 11 | Does praise for effort vs ability affect persistence in children? | Type of praise | Time spent on a hard puzzle |
| 12 | Does reading aloud to toddlers increase vocabulary? | Daily reading vs none | Words known at 24 months |
| 13 | Does class size affect test performance? | Small vs large classes | Standardized test score |
| 14 | Does screen time before bed affect sleep in teens? | Screens off 1 hour before bed vs no rule | Minutes to fall asleep |
Clinical and health
| # | Study | IV | DV |
|---|---|---|---|
| 15 | Does CBT reduce anxiety more than a waitlist? | CBT vs waitlist | Anxiety questionnaire score |
| 16 | Does exercise reduce symptoms of depression? | 30 minutes of exercise 3 times a week vs none | Depression scale score |
| 17 | Does mindfulness reduce exam stress? | Mindfulness training vs none | Self-reported stress (0 to 10) |
| 18 | Does a placebo pill reduce pain reports? | Placebo vs no pill | Pain rating |
Biological and perception
| # | Study | IV | DV |
|---|---|---|---|
| 19 | Does caffeine improve alertness? | Caffeine dose (0, 100, 200 mg) | Alertness test score |
| 20 | Does room temperature affect concentration? | Temperature (18°C vs 26°C) | Errors on an attention task |
| 21 | Does colour affect perceived taste? | Drink colour (red vs clear) | Sweetness rating |
| 22 | Does hunger affect food-related attention? | Fasting vs fed | Time looking at food images |
Correlational examples (no manipulation)
In correlational studies, researchers don't manipulate anything, so strictly there's no IV or DV. Many textbooks call them predictor and outcome (or criterion) variables.
| # | Study | Predictor | Outcome |
|---|---|---|---|
| 23 | Is hours of study related to GPA? | Hours of study per week | GPA |
| 24 | Is social support related to resilience? | Social support score | Resilience score |
| 25 | Is age related to reaction time? | Age | Reaction time |
Operational definitions
An operational definition says exactly how a variable is measured or manipulated. "Stress" is a concept; "score on the Perceived Stress Scale" is an operational definition.
| Concept | Weak | Operational definition |
|---|---|---|
| Memory | How well people remember | Number of words correctly recalled from a 20-word list after 5 minutes |
| Sleep deprivation | Being tired | Sleeping 4 hours or less the night before testing, confirmed by sleep diary |
| Aggression | Being mean | Number of hostile comments coded by two independent raters |
| Anxiety | Feeling nervous | Total score on the GAD-7 questionnaire |
Other variables you'll be asked about
| Variable | Meaning | Example (study 1: music and recall) |
|---|---|---|
| Extraneous variable | Anything other than the IV that could affect the DV | Time of day, noise outside the room |
| Confounding variable | An extraneous variable that changes with the IV | Music group tested in a noisier room |
| Control variable | Kept the same for all participants | Same word list, same timing, same instructions |
| Participant variable | Differences between people | Musical training, native language |
Common exam mistakes
| Mistake | Fix |
|---|---|
| Naming the topic, not the variable: "IV is music" | Name the levels: "music vs silence" |
| Vague DV: "memory" | Say how it was measured: "number of words recalled" |
| Calling a correlational predictor an IV | Use predictor and outcome when nothing is manipulated |
| Mixing up IV and DV in "effect of" questions | The IV comes after "effect of"; the DV comes after "on" |
Frequently asked questions
What's the easiest way to tell IV from DV?
The IV is the cause the researcher changes; the DV is the effect they measure. Use the sentence "The effect of [IV] on [DV]."
Can a study have more than one IV?
Yes. A factorial design has two or more IVs, for example music (on or off) and time of day (morning or evening).
Can a study have more than one DV?
Yes, such as measuring both recall and recognition. Each is analyzed separately or together with multivariate tests.
Is age an independent variable?
Age can't be manipulated, so in a strict sense it's a participant or quasi-independent variable. Many textbooks still list it as an IV in quasi-experiments.
What is an operational definition?
A precise statement of how a variable is measured or manipulated, so another researcher could repeat the study.
What's the difference between extraneous and confounding variables?
An extraneous variable could affect the DV. It becomes a confounding variable when it changes systematically with the IV.
Related guides and tools
- How to write an APA 7 psychology lab report
- How to write a research paper
- Free APA 7 citation generator
- Psychology assignment help
Sources: American Psychological Association, APA Dictionary of Psychology (entries for independent, dependent and confounding variables). Study examples are illustrative designs, not claims about published results.
