N-Back Task

Field	Value
Name	N-Back Task
Version	main (1.0)
URL / Repository	https://github.com/TaskBeacon/T000008-nback
Short Description	An N-Back task with 1-back and 2-back conditions.
Created By	zh1peng
Date Updated	2025/07/24
PsyFlow Version	0.1.0
PsychoPy Version	2025.1.1
Modality	Behavior/EEG
Language	Chinese
Voice Name	zh-CN-YunyangNeural

1. Task Overview

This task is a classic N-Back cognitive test. Participants are shown a sequence of digits and must determine if the current digit matches the one presented 'N' trials ago. The task includes two blocks: a 1-Back block and a 2-Back block.

2. Task Flow

Block-Level Flow

Step	Description
1. Instruction	For each block (1-Back then 2-Back), instructions are displayed. The first half of the blocks are 1-Back, the second half are 2-Back.
2. Trial Execution	The block runs for a set number of trials, as defined in config.yaml.
3. Block Break	After each block, a break screen is shown with the accuracy for the 'match' trials in that block.
4. Goodbye	After all blocks are complete, a "goodbye" message is displayed.

Trial-Level Flow

Step	Description
1. Digit Presentation	A digit is presented on the screen for the duration specified by probe_duration. The participant can respond during this time.
2. Inter-Trial Interval (ITI)	A blank screen is shown for the duration specified by iti_duration.

Controller Logic

Controller Element	Description
Condition Generator	generate_nback_conditions generates match_<digit> / nomatch_<digit> sequences with match-ratio and run-length constraints.
Block Mapping	First half of blocks run 1-back, second half run 2-back.
Runtime Context	Trial phases are emitted as nback_probe_response and inter_trial_interval via set_trial_context(...).

Other Logic

Function	Description
generate_nback_conditions	This function generates the sequence of trials for each block. It ensures a specific ratio of 'match' to 'non-match' trials, and controls for the number of consecutive 'match' trials.

Runtime Context Phases

Phase Label	Meaning
nback_probe_response	nback probe response stage in src/run_trial.py responder context.
inter_trial_interval	inter trial interval stage in src/run_trial.py responder context.

3. Configuration Summary

a. Subject Info

Field	Meaning
subject_id	Subject Identifier
subname	Subject Name
age	Age
gender	Gender

b. Window Settings

Parameter	Value
size	[1920, 1080]
units	deg
screen	1
bg_color	gray
fullscreen	True
monitor_width_cm	60
monitor_distance_cm	72

c. Stimuli

Name	Type	Description
stim_digit	text	The digit presented to the participant.
stim_iti	text	A blank stimulus for the inter-trial interval.
instruction_1back	textbox	Instructions for the 1-Back block.
instruction_2back	textbox	Instructions for the 2-Back block.
block_break	text	Feedback shown between blocks.
good_bye	textbox	Final message at the end of the task.

d. Timing

Phase	Duration
probe_duration	0.8
iti_duration	1.2

e. Triggers

Event	Code
exp_onset	98
exp_end	99
block_onset	100
block_end	101
match_onset	2
nomatch_onset	3
key_press	4
no_response	5

4. Methods (for academic publication)

Participants perform an N-Back task, a continuous performance paradigm used to measure working memory. The experiment is divided into two blocks: a 1-Back and a 2-Back condition. In each trial, a digit (1-9) is presented on the screen. Participants are instructed to press the spacebar if the current digit is identical to the digit presented N trials previously (a "match").

The task begins with a 1-Back block, followed by a 2-Back block. Each block consists of 20 trials. The sequence of stimuli is pseudo-randomly generated to contain approximately 30% match trials. A digit is displayed for 800ms, during which a response can be made. This is followed by a 1200ms inter-trial interval. Feedback on accuracy for match trials is provided at the end of each block.