Every demo below is a working Lens study. Each one opens in its own tab too, which is easier on a phone. Change /en at the end of a link to /fa or /ar to see Persian or Arabic, laid out right to left.

Survey pages

Text, country, choice and slider questions. Missing answers are pointed out under the question, and horizontal choices stack on phones. Open in a new tab

Reaction-time tasks

Stimulus onset and response times are recorded with the browser’s high-resolution clock.

Stroop. Open in a new tab

Go/No-Go, with letters or icons. Open in a new tab

Two-choice task (2-alternative forced choice). A star appears on the left or right: blue means answer on the same side, yellow the opposite side. Open in a new tab

N-back. Open in a new tab

Balloon Analogue Risk Task (BART). Open in a new tab

Economic games

Dictator game. Participants split tokens by dragging them between the two sides. Open in a new tab

Ultimatum game, against pre-recorded opponents. This one adds + and − buttons next to dragging, which helps on small screens. Open in a new tab

Dice allocation. Each round there are two dice, a blue one and an orange one. Participants decide privately which is theirs and which is the other person’s, roll both, then give each die to a person and get the points on theirs. The private choice isn’t recorded, so self-serving choices show up only over many rounds: honest players keep the higher die about half the time. Based on a Cut prototype from 2018. Open in a new tab

Live two-player ultimatum game. Participants are paired as they arrive, first come, first served. If no one else arrives within the time the study sets, a computer partner plays instead, following one of Cut’s original strategies. A debrief after the game says which it was. To play both sides yourself, open the game in two windows; to meet the computer partner, open it once and wait about 20 seconds.

Old designs

Lens 1 (release v1.0) still runs every earlier study unchanged: 2-alternative forced choice, task switching, simplified task switching, and every classic task in one study, adapted from the instrument we used to study the Ramadan fast (Rad, Ansarinia & Shafir, 2023).

How a study is written

A study is one JSON file: a list of pages, shown in order, each with its own settings. This one is a welcome page followed by ten balloons of BART:

{
  "studyId": "my-study",
  "redirectTo": "https://app.prolific.com/submissions/complete?cc=XXXX",
  "views": [
    { "id": "welcome", "type": "text2", "instruction": true,
      "text": "Welcome! This takes about 10 minutes." },
    { "id": "bart", "type": "bart2", "reward": 5, "maxPumps": 20,
      "safePumps": 1, "trials": 10 }
  ]
}

Once published, it runs at https://lens.cut.social/#/my-study/en. The responses come back the same way: one record per participant, with each page’s settings next to the answers, so the data describes itself.

You don’t have to write the file by hand. The study builder gives every page a form, previews it as participants will see it, flags problems as you type, and keeps the text for each language in the study file. The Lens README lists every page type and option.