Task 1

Task 1 - Coloured Squares

Outline

This task presents participants with an array of stimuli (differently coloured squares), followed by a probe stimulus (a single coloured square). Participants have to indicate whether the probe stimulus appeared in the array.
The difficulty of the task is adaptive, so that as participants answer correctly the task gets harder (more stimuli in the array), and as they answer incorrectly the task gets easier (fewer stimuli in the array). This uses a staircase approach to adapting the diffculty (i.e. N correct/incorrect answers makes the task harder/easier; where N is specified in the config file by staircaseUp/staircaseDown)

Config

This section lists all of the config options available to change and what they do. These do no have default values, so will need to be set to something for the experiment to work.
For more general information about config files (e.g. their structure) see the Config info page

run

Flag to include/exclude task from overall experiment

practice

Note

Not currently used

Flag to include/exclude practice trials

fixationDuration

Duration (ms) the fixation screen is displayed for

fixationPostTrial

Duration (ms) of blank screen after the fixation screen

stimulusDuration

Duration (ms) the stimulus is displayed for

stimulusPostTrial

Duration (ms) of blank screen after stimulus

nTrialReps

Number of times the trials should be repeated.
By default there are two types of trials ('Probe present in array' and 'Probe absent in array'; distrubuted 50:50), so this value should be half of the total number of trials you want to include.

stimDims

Array contianing the dimensions of the stimuli in pixels: [w, h].

radius

Distance in pixels of the centre of each the stimuli from the centre of the screen

radiusJitter

Array of 2 integers indicating the bounds of jitter for the radius. 1st value is the lower bound and second is the upper bound. e.g. if radius is set to 100 and radiusJitter is set to [-10, 10] then the acutal value of radius will be somewhere on a uniform distribution between 90 and 110.

angleJitter

Array of 2 integers indicating the bounds of jitter for the angle. 1st value is the lower bound and second is the upper bound. e.g. if the angle is set at 45 degrees and angleJitter is set to [-2, 2] then the actual angle will be somewhere on a uniform distribution between 43 and 47.

colours

An array of potential colours for the stimuli. There should be at least 1 + (the value of the maxValue option) stimuli in the array.
e.g. If maxValue: 8 then there should be 9 items in the array.

Please see the Specifying colours page for more info on how colours can be specified in this array.

nPositions

Integer indicating the number of different potential positions available for stimuli to appear in. Also determines the spacing angle between the stimuli (e.g. 8 positions = 45 degree spacing, 10 positions = 36 degree spacing, 12 positions = 30 degree spacing).
These positions are arranged in a circle around the centre of the screen. They are equally spaced and the distance from the centre is defined by the radius parameter (see below).

startValue

The starting number of stimuli

minValue

Minimum number of stimuli

maxValue

Maximum number of stimuli

staircaseUp

Number of correct answers to move up the staircase (i.e. increase the diffculty)

staircaseDown

Number of incorrect answers to move down the staircase (i.e. decrease the diffculty)

Data

Data for task 1 are recorded in rows where the column Screen == probe and the column Task == 1 Columns of interest include:

• novel_probe: Was the probe presented novel (i.e. not in the memory array)? [true or false]
• expected_response: The expected correct response [0: yes or 1: no]
• response: The participants actual response [0: yes or 1: no]
• accuracy: Was the response given correct [true or false]
• RT: Reaction time of the response [in ms]
• Probe_colour: Colour of the probe stimulus
• nItems: The number of targets present on screen