Biology IA · C · Interaction and interdependence · topic 16 of 25

Practice and reaction time · IB Biology IA idea: guide, sample graph and step-by-step plan

simple kit, so make the analysis count

Does a simple reaction test get better with practice? You're going to turn a falling ruler into numbers and see whether the nervous system learns.

Difficulty●○○ Gentle
KitMetre rule (a 30 cm ruler is too short for slow catches), a helper, a table, a spreadsheet
TimeAbout 10 hours
FitsSL and HL
  • ✓ you like sport, gaming or the brain
  • ✓ you can recruit willing volunteers
  • ✓ you want a quick, low-cost set-up

The big idea

← this is your RQ hook!

When the ruler drops, the time you take to catch it is your reaction time. Free fall gives t = √(2d/g), so the distance d is converted into time. With practice the pathway from eye to hand may get faster, or just more predictable. Your job: separate real improvement from anticipation, by varying the release delay, and use enough volunteers that the pattern is not just one person. The experiment is simple, so the analysis and the ethics must be careful.

Make it yours: pick one twist

Copying a classic won't show your choices. Pick one of these (or invent your own) and your IA becomes yours.

Swipe for more twists →

Dominant vs non-dominant hand

Repeat the practice series with each hand.

→ A second variable inside each volunteer; a paired comparison between hands.
Rest between blocks

Compare practice in one block with practice split over several days.

→ Tests spaced practice. Needs more time and agreement from volunteers.
Auditory cue

Replace sight of the ruler with a sound to start the catch (a helper clap).

→ A different sense; your analysis compares two kinds of cue.
Distraction

Add a simple, safe task such as counting backwards while catching.

→ Tests attention. Keep it mild, and only with volunteers who agree.
Compare age or experience groups

Compare gamers or athletes with non-gamers, with their consent.

→ Between-groups comparison, with more thought on sampling and fairness.
Change the context

Link to driving, sport or esports.

→ Gives your trial range a purpose; the experiment stays the same.

Your Biology IA research question: run the check

write it FIRST, then check it

Write your own question first. Then make sure it ticks every box:

  • Names the independent variable (trial number or number of attempts) and the range, say 1 to 30.
  • Names the dependent variable (reaction time calculated from d, with the formula and the units).
  • Says how many volunteers, how they were chosen, and what you did to avoid anticipation.
  • Says what stays fixed (hand, ruler, helper, position, time of day) and how you check each.
  • Is narrow enough for about 10 hours, and states honestly what a small sample can and cannot show.

Get your RQ checked · S$29

The set-up

One way to set it up. Draw your own version, with your real positions, for the Method section.

dt = √(2d / g)g = 9.81 m s⁻²helper: vary the delaybefore each dropread d where your thumbstops the rulerzero mark level withthe top of the thumbsame hand, same ruler,same helper each time

How your Biology IA could be laid out

The usual order for a topic like this, what each part needs to show, and roughly how much of your 3,000 words it takes. The words are all yours.

Research question and context~250
Your question, why reaction time matters (driving, sport, esports), and what you expect to happen with practice.
Background biology~450
The pathway from eye to brain to hand (a learned reaction, not a reflex), the nervous system, and ideas about learning and anticipation; the free-fall formula; what your graph should look like if your prediction holds (cite your source).
Variablestable
Independent, dependent and controlled variables, with how each is set, measured or kept constant, and why.
Method~450
The volunteers and how you recruited them, the exact test procedure, the random delay, how many attempts and breaks, and enough detail to copy.
Safety, ethics, environment~120
Informed consent, the right to stop and withdraw data, anonymous codes, parental or school consent for under-18s as your school requires, no drugs, caffeine or sleep deprivation, and a ruler dropped onto a soft surface away from faces.
Raw datatable
One clear table: volunteer code, trial, distance d, units and uncertainties in the headers.
Processing~250
Converting d to time, the uncertainty of the time, the mean and spread for each trial or block, and one worked example of each calculation.
Graphs and analysis~400
The graph you choose and why, SE error bars, and a paired test (paired t-test, or Wilcoxon signed-rank) on each volunteer's first and last blocks, with its conditions checked. Each volunteer is one replicate, not each catch.
Conclusion~400
Answer the question with numbers and uncertainties, link to the biology, compare with published reaction times and state limits.
Evaluation~550, the biggest part!
Weaknesses ranked by effect on your result (small sample, anticipation, fatigue), and improvements linked to each.
Referencesnot counted
Every source for the biology and the formula.

What your Biology IA graph could look like

error bars on EVERY point ✓

Made-up data, to show you the form of a strong graph, not the answer. Your volunteers might improve fast, slowly or not at all. example only

051015202530180200220240260280Trial number (attempt)Mean reaction time t / ms (bars: SE of n volunteers)levelling-off curveno change with practicemean of volunteers, with error barsdoes the curve level off?where, and why?ILLUSTRATIVE · MADE-UP DATA
  • Trial number has no uncertainty, because you set it exactly. Say that, instead of putting a bar on it.
  • Each point is a mean across several volunteers, so the bars show how people differ. A single volunteer is a case study, not a trend.
  • The y-axis does not start at zero, so say so. The change is small compared with the whole reaction time.
  • A flat line is drawn too. A strong conclusion says whether the first and last attempts differ by more than the spread.
  • Another graph to consider: plot each volunteer's own first-five average against last-five average as a paired comparison. Same volunteers, so a paired test, with its conditions checked.

Which uncertainty matters most?

rank them: don't just list them

Rank by the effect on your result (mean reaction time, assumed 220 ms), not on raw readings. The ruler reading is small. The spread between people matters most, and only more volunteers will shrink it.

Spread between volunteers (SD 25 ms, n = 8)4%Ruler reading (±0.5 cm at d = 24 cm)1%Judging thumb position (±0.3 cm)0.6%biggest effect: discuss this first!% uncertainty in mean timeILLUSTRATIVE · MADE-UP NUMBERS

Your game plan

don't skip the trial run! it saves you weeks

Tick steps off as you go. We'll remember on this device.

0 of 10 done

  1. Read and predictFind out how reaction time is made up and what is known about practice effects. Write down your prediction before you start.
  2. Plan the ethics firstDecide how you will ask for consent, how volunteers can stop, and how data are kept anonymous. Get your teacher's agreement before recruiting.
  3. Trial run (1 lesson)Try the test with a couple of people. Is the release delay unpredictable? Can you read d to the nearest 0.5 cm? Is the ruler held straight? Fix the problems now.
  4. Decide range, volunteers and breaksChoose how many attempts and volunteers, how the delay is varied, and when volunteers rest. Write down why for each choice.
  5. Fix the set-upSame table height, same arm position, same ruler, same helper. Write down how each is kept the same.
  6. Collect the dataRecord d straight into your table with the volunteer code. Randomise the delay. Note when someone tires or loses focus.
  7. ProcessConvert d to t with its uncertainty. Calculate the mean and spread per trial or block across volunteers.
  8. Graph and analysePlot with error bars. Choose a comparison that suits repeated measures on the same people, and check the conditions of any test.
  9. EvaluateWhich weakness mattered most? Use your own spread to rank them. Make every improvement specific.
  10. Write, then checkWrite in the order of the layout. Run the checklist below before your teacher's draft.

Biology you'll need

Traps to avoid in this Biology IA

  • A predictable release rhythm: volunteers anticipate and the time reflects timing, not reaction.
  • One volunteer, or three, called 'a trend'. State the limits of a small sample.
  • Treating all trials as independent when they come from the same people.
  • Fatigue after many attempts hiding or imitating a practice effect.
  • Different helpers or ruler grip between volunteers, changing the start of the fall.
  • Mixing up distance and time: a smaller reading means a faster reaction, not a slower one.
  • Volunteers who are not told they can stop, or data that can be traced to a person.

More Biology IA ideas like this

Make sure it's yours

This guide shows how a topic like this is usually approached. It is not an IA. Your question, choices, data, analysis and words must be your own: change something, tell your teacher where the idea came from, and follow your school's rules on outside help.

Get your RQ checked · S$29