Today you build two scientific arguments. You will generate your own data at the bench, read a pattern out of it, and then write a claim, the evidence behind it, and the reasoning that joins the two.
- CClaim — blue
- EEvidence — yellow
- RReasoning — green
Five jobs. Pick one each.
- Driver
- works the bench. Changes one thing at a time and says each change out loud.
- Recorder
- fills the tables as the numbers appear. Nothing goes in later from memory.
- Grapher
- owns the graph of your three doses. Axes and labels before any points.
- Skeptic
- asks one question of every sentence the group writes: is that a claim, evidence or reasoning?
- Reporter
- reads your finished argument to the class.
Your typing is kept in this browser on this device. Reloading will not lose it.
Part A — Spot the argument
Eight minutes. Warm-up only.
- Pick a highlighter.
- Click a sentence to colour it. Click it again to clear it.
- Some sentences are background — they set the scene and do no C, E or R work. Mark those with the grey pen.
- Press Check my labels.
Paragraph 1
An SSRI does not start working on the day the patient takes the first tablet. The drug reaches the serotonin pump and blocks it within hours of that first dose. Patients are nevertheless told to allow four to six weeks before judging whether it is helping. The gap between those two facts cannot be the drug arriving late, because it is already sitting on its target. It is the neuron answering back — rising serotonin makes the cell slow its own firing, and that brake only fades over weeks.
Paragraph 2
Dopamine neurons in the midbrain send their axons to the striatum. In the bench model, a drug that reverses the dopamine pump raises the background level to about eleven times resting. The reward bursts in that same run rise only about a third above the new background, against nearly four times above it in a normal synapse. Flooding the gap therefore makes a reward harder to notice, not easier. A receiving cell can only register a change from the level it has been sitting in, so lifting the floor and the ceiling together shrinks the difference it has to work with. Each run covers a twenty-second window.
Part B — Your three doses
Thirty minutes. Your group has three doses of its own. No other group has the same three.
Step 1 — Claim your group
Step 2 — Twelve readings: four days at each of your three doses
- Pick the small dose. Set the day slider to 1 and press Record this reading.
- Repeat at days 7, 14 and 28. Four rows for that dose.
- Now the middle dose, then the big dose. Same four days each. Twelve rows in all.
| Which dose | — |
|---|---|
| Pumps still working | — |
| Day | 1 |
| How fast the neuron is firing | — |
| Brake still left | — |
| Serotonin in the gap | — |
| Dose | Day | Firing | Brake | Gap |
|---|
Step 3 — Three numbers off your own table
- How much higher the big dose got: the big dose’s day 28 ÷ the small dose’s day 28. One decimal place.
- How far along the small dose was halfway through: its day 14 ÷ its day 28, as a percentage. Nearest whole number.
- The same for the big dose: its day 14 ÷ its day 28, as a percentage.
Step 4 — Your three curves on one set of axes
- Check your twelve points against the graph below.
- Copy it onto your board, axes labelled.
- Answer the two questions underneath. They are the evidence for Part C.
| Dose | Pumps still working | Day 1 | Day 28 | Day 14 as % of day 28 |
|---|
- Which of your three doses ended highest? Which was furthest along by day 14?
- So does more drug get there faster, or slower?
Part C — Build argument 1
Fifteen minutes. Use your own three doses from Part B as your evidence.
Marisa, 26. Day 4 on an SSRI. She feels sick, she is sleeping badly, and her mood has not shifted. She asks whether a higher dose would make it work sooner.
The question to answer: would a higher dose make it work sooner?
CClaim
Answer the question in one sentence. Take a position.
Stuck? “A higher dose would…” · “No, because…”
EEvidence
Give the numbers from your own three doses that support your claim. Say which dose each came from.
Stuck? “Our big dose reached __ by day 28 while our small dose reached only __…” · “By day 14 our small dose was __ % of the way to its finish, but our big dose was only __ %…”
RReasoning
Explain why those numbers lead to your claim. Name the thing in the synapse that is doing it.
Stuck? “This happens because…” · “Since the dose sets __ but the __ sets __…”
Argument 1, as one paragraph
Read it aloud. If a listener could ask “how do you know?” and you have already answered it, you are done.
Part D — Four setups at the dopamine bench
Twenty minutes. Press each setup, let it run, read the row it writes.
- Press each of the four setups in turn and let the twenty seconds play out.
- Each run writes its own row into the table. Copy the table to your board.
- Then match each setup to the step the drug is working on, and press Check.
| Setup | Background | Peak | Burst ÷ background | Reward signal |
|---|---|---|---|---|
| 1. Normal | — | — | — | — |
| 2. Cocaine | — | — | — | — |
| 3. Amphetamine type | — | — | — | — |
| 4. Nicotine | — | — | — | — |
Which step is each drug working on?
Answer from your numbers, not from the name on the button.
On the board:
- Three of these four raise the background. Only one of them leaves the bursts standing out as far as normal. Which?
- Rank the four by peak dopamine. Now rank them by burst ÷ background. Say in one sentence why the two orders disagree.
Part E — Build argument 2
Twenty minutes. You need your Normal row from Part D.
Tyler, 24. Used a stimulant heavily for two years, stopped six weeks ago. Past withdrawal, not craving. Says nothing is fun — food, music, his daughter’s birthday.
The question to answer: his dopamine is normal, so where has the problem moved to?
Step 1 — Run his setup and compare it with Normal
| Reading | Normal | Tyler | Same? |
|---|---|---|---|
| Background | — | — | — |
| Peak during a reward | — | — | — |
| Burst ÷ background | — | — | — |
| Receptors left | — | — | — |
| Reward signal | — | — | — |
Step 2 — One number off that table
Tyler’s reward signal as a percentage of the normal reward signal. Nearest whole number.
Step 3 — The argument
CClaim
In one sentence, where has the problem moved to?
Stuck? “The problem is no longer… it is…”
EEvidence
Give the rows that are normal and the row that is not. Numbers, both columns.
Stuck? “At the bench his background was __ and normal was __, but his reward signal was __ against __…”
RReasoning
Explain why the same dopamine can produce a smaller signal.
Stuck? “A message is only as big as what receives it, so…”
Argument 2, as one paragraph
Step 4 — What this bench cannot tell you
Tyler’s next question is how long. Nothing you measured today answers it. On the board, write what you would have to measure to give him a timeline.
Before you leave
- Both arguments on the board, each with its three parts in the three colours.
- Your twelve readings and your summary table.
- Your graph, with all three doses on it, axes labelled.
- One sentence: name the part of each argument your group found hardest to write, and why.
The two benches are teaching models. The numbers are chosen to be readable and to behave the way the real system behaves; they are not clinical values. This page covers how the drugs act on pumps and receptors only — there is no dose, route or product information on it. Your typing is saved in this browser only.