Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 22, 2012
Last Modified: January 27, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the Dictator Game, a socio-economic game about the allocation of monetary resources to study prosocial behavior. In the Dictator Game participants get the choice to allocate money in either a more pro-social or less pro-social manner without having to take a possible response/revenge of their opponent into account.
The implemented procedure is based on Brockelbank et al (2011).
Brocklebank, S., Lewis, G.J, & Bates, T.C. (2011). Personality accounts for stable preferences and expectations across a range of simple games. Personality and Individual Differences, 51, 881-886.
3 minutes
A participant (= Player B) gets to allocate money (resources) that is presented in a decision tree format to another Player A and herself.
The participant (Player B) has the choice to allocate the money in a more or less "prosocial" manner. If the participant consistently chooses the dedicated 'pro-social' option, Player A ends up with about $1300 more (hypothetical) money than the participant. By choosing consistently the non-social option, the participant ends up with about $1300 more (hypothetical) money than Player A.
1) Number of Games Run:
This script runs 6 dictator game trials (default).
to change the number of games played, edit
a) LISTS: list.leftA, list.leftB, list.rightA, list.rightB to reflect the desired number of trials/amounts
b) BLOCK: adjust the number of trials run under block.Dictator
2) Amounts:
The designated 'left' and 'right' amounts allocated are stored in list.leftA, list.leftB,
list.rightA and list.rightB. The default amounts provided in this script are the ones used by Brocklebank et al (2011).
Designated 'left' = amounts that Brocklebank et al (2011) report to be the 'left' amounts in table 1.
(in this particular script, the designated 'left' responses could be interpreted as the more "prosocial" choices)
The amounts can be easily adapted by each experimenter. Furthermore, by default the amounts are presented in a
sequential order for each participant. To change presentation to random, change list.trialOrder.
3) Within-participant control of response keys:
Presentation of designated 'left' amounts randomized without replacement within participants.
Of the 6 games (default), 3 randomly determined trials will display the designated 'left' choices on the left branch,
the remaining 3 will display them on the right branch.
!!!
=> values.responseBranch reflects the actual branch chosen by the participant.
=> 'response' reflects if participant chose the designated 'left or 'right' amounts
optional opponent pics -> see section Editable Stimuli
Instructions are not original to the task. They are provided by Millisecond.
They can be edited in file dictatorgame_instructions_inc.iqjs
File Name: dictatorgame_summary*.iqdat' (Inquisit Lab: one data file per participant)
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
Parameters Settings |
|
| showOpponentPic | 1 = a picture of an opponent is displayed on decision tree screen (fine tune picture under STIMULUS -> picture.opponent] 0 = no opponent picture is displayed (default) |
| showComputerTotal | 1 = show win status of Player A; 0 = do not show win status of player A (default) |
| showParticipantTotal | 1 = show win status of Player B; 0 = do not show win status of player B (default) |
| posttrialPause | Sets the posttrialpause (default = 1000ms) |
Performance Metrics |
|
| countLeft | Sums up all designated 'left' choices (more prosocial, altruistic choices) |
| countRight | Sums up all designated 'right' choices |
| totalComputer | The total amount Player A wins |
| totalParticipant | The total amount Player B wins |
| dTotal | The difference in monetary outcomes (positive favors participant, negative favors computer) |
File Name: dictatorgame_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockcode | The name the current block (built-in Inquisit variable) |
| blocknum | The number of the current block (built-in Inquisit variable) |
| trialcode | The name of the currently recorded trial (built-in Inquisit variable) |
| trialnum | The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file |
| gameCounter | Tracks the number of games played |
| branch | 0 = designated "left" amounts displayed on left 1 = designated "left" amounts displayed on right |
| leftAvalue-rightBvalue | Contain the designated 'left' and 'right' value amounts for player A and player B these amounts can appear on the left OR right of the decision tree |
| responseBranch | The actually selected response branch B1 (choice B on the left) or B2 (choice B on the right) if the participant selected a designated 'left' amount but the amount was presented on the right, ResponseBranch = B2 but response = left (designated 'left' amount) If a participant always selects the designated 'left' values, Response = left for all trials, but ResponseBranch will reflect the actual branch chosen. |
| response | The participant's response (choice of designated 'left/favoring others' vs. 'right' amount) |
| latency | The response latency (in ms) |
| countLeft | Sums up all designated 'left' choices |
| countRight | Sums up all designated 'right' choices |
| totalComputer | The total amount Player A wins |
| totalParticipant | The total amount Player B wins |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Design |
||
| pictureintro | 1 = a separate picture introduction of the co-player is displayed before decision tree screens come up (fine tune picture under STIMULUS -> picture.opponentPic] 0 = no separate picture introduction of the co-player | 0 |
| showOpponentPic | 1 = a picture of an opponent is displayed on decision tree screen (fine tune picture under STIMULUS -> picture.opponent] 0 = no opponent picture is displayed | 0 |
| showComputerTotal | 1 = show win status of Player A; 0 = do not show win status of player A | 0 |
| showParticipantTotal | 1 = show win status of Player B; 0 = do not show win status of player B | 0 |
Timing Parameters |
||
| posttrialPause | Sets the posttrialpause in ms | 1000 |