The coin-flip bet.
In a bet where you lose 100 TL (Turkish lira) on tails and win X TL on heads, how big does X have to be before you say 'I'll play'?
Original study
- Kahneman, D., & Tversky, A. (1979). Prospect theory: An analysis of decision under risk. Econometrica, 47(2), 263–291. Source
- Tversky, A., & Kahneman, D. (1992). Advances in prospect theory: Cumulative representation of uncertainty. Journal of Risk and Uncertainty, 5(4), 297–323. Source
- Samuelson, P. A. (1963). Risk and uncertainty: A fallacy of large numbers. Scientia, 98, 108–113. Source
- Redelmeier, D. A., & Tversky, A. (1992). On the framing of multiple prospects. Psychological Science, 3(3), 191–193. Source
- Gächter, S., Johnson, E. J., & Herrmann, A. (2022). Individual-level loss aversion in riskless and risky choices. Theory and Decision, 92(3–4), 599–624. Source
- Brown, A. L., Imai, T., Vieider, F. M., & Camerer, C. F. (2024). Meta-analysis of empirical estimates of loss aversion. Journal of Economic Literature, 62(2), 485–516. Source
- Walasek, L., & Stewart, N. (2015). How to make loss aversion disappear and reverse: Tests of the decision by sampling origin of loss aversion. Journal of Experimental Psychology: General, 144(1), 7–11. Source
Our adaptation
An eight-gamble adaptation of Kahneman and Tversky's (1979) measurement of loss aversion with mixed gambles. In each gamble there is a 50% chance of losing 100 TL and a 50% chance of winning X TL (X = 50, 100, 150, 200, 250, 300, 400, 600); gambles are presented in a random order per participant and answered 'I'd play' or 'I wouldn't'. The last round asks about the 150, 200 and 300 TL gambles as bundles of 10, as in Samuelson's (1963) discussion.
Differences from the original study
- Money is hypothetical.
- The λ estimate is a simple approximation assuming linear utility and equal probability weighting.
- The range of gains offered can influence λ (Walasek and Stewart, 2015).
Measured variables
The columns of the open data file. List fields are expanded into numbered columns (for example rt_60, est_3); JSON columns contain only numbers and fixed stimulus names.
| Column | Type | Description |
|---|---|---|
accept | JSON | Decision on each single gamble: {"X": true = would play} (X = gain amount in TL). |
bundle | JSON | Decision on the bundles of 10: {"X": true = would play} (X = 150, 200, 300). |
lambda | number | Loss-aversion coefficient (λ), computed on the server from the accepted gambles (rule: if k gambles were accepted, the threshold is the smallest of the k largest gains; λ = threshold / 100). If no gamble was accepted, 7 is recorded (meaning λ > 6, a censored value). |
Columns present in every file (14)
row_id | string | Row code. Regenerated at random in every release; it does not identify a person and cannot be matched across releases or experiments. |
experiment | string | Short name of the experiment (URL slug). |
experiment_version | integer | Version of the answer format. For experiments whose format changed, only the current format is published. |
date | YYYY-MM-DD | YYYY-Www | YYYY-MM | Day the answer was given (Istanbul time). If fewer than 5 answers share the same day, language and device, it is coarsened to the ISO week, and to the month if that is still too few. |
date_precision | day | week | month | Precision of the date column. |
lang | tr | en | (boş) | Interface language. Language recording started in the first week of October 2026; for earlier answers it is known only in experiments whose stimuli depend on the language, and empty otherwise. |
device | desktop | mobile | tablet | (boş) | Device class reported by the browser (class only; browser details are neither stored here nor published). |
source | site | embed | Where the answer came from: the balabs site or the experiment embedded on another site. The embedding site is not published. |
mode | free | daily | challenge | race | session | (boş) | Play mode in scored experiments: free play, daily round, challenge, race room, experiment session. Empty for unscored experiments and for older answers that did not store it. |
color_vision | normal | rg | by | contrast | (boş) | In color-based experiments, the color vision mode the participant chose: normal, red-green, blue-yellow or high contrast. Stimuli are generated along different axes per mode, so compare within a mode. Empty for other experiments. |
first_play | 1 | Every row is a participant’s first play of this experiment (always 1). Replays are stored only as leaderboard scores and are not part of the open data. |
seen_before | yes | no | unsure | (boş) | Participant’s own report of whether they had seen this experiment or its known answer before (in experiments that ask). |
duration_s | number | Time from the start of the experiment to submitting the answer, in seconds (measured in the browser, 0.1 s). |
play_score | number | Leaderboard score of the first play (scored experiments; defined on the method card). Empty for unscored experiments. |
Exclusion criteria
The server expects a yes/no answer for all eight gambles; incomplete submissions are rejected. We recommend reporting non-monotonic choices (e.g. accepting 200 but rejecting 250) separately.
- Only each participant's first answer to this experiment; replays are not included.
- Simulated rows, bots, banned and sample accounts are not included.
- Answers before 3 October 2026 are not included (the first day the open data notice was live).
Scoring
This experiment has no leaderboard score. The crowd result is the λ distribution and the acceptance rate of the bundled gambles.
Version notes
- October 2026
The loss-aversion coefficient (λ) rule changed: if k bets were accepted, the threshold is the smallest of the k largest gains. The lambda column in the open data is recomputed from the choices with this rule for every row.
- October 2026
The interface language (lang) started being stored with each answer; for earlier answers it is known only in experiments whose stimuli depend on the language, and empty otherwise.