Introduction

Spatial orientation occurs when attention is drawn to a specific location. Attention can be drawn to a location due to the appearance of a stimulus. In the Posner task, this drawing of attention to a location is called cueing.

The basic phenomenon in the Posner task is that we are quicker to detect objects at places that have been cued before, that is, where previously a salient stimulus was presented (Posner, 1980). An example of this can be a flash at a location, which makes your eyes almost automatically make an eye-movement (i.e., saccade) to that location.

Researchers distinguish between valid and invalid cues. Valid cues inform a participant about the location where something task-relevant will happen (e.g., a flash at the location where a to-be detected stimulus will appear); invalid cues occur at a location where nothing relevant will happen.

Further, there are informative cues and uninformative cues. For example, if the location of a cue is random, it is uninformative. In some experiments (like in the example below), a cue can have 75% validity (in 3 out of 4 times, it occurs at the location where the to-be detected stimulus will appear).

Valid cues have a relatively strong effect on detection, as can be experienced in the example below. The larger the information content of the cue (in the example 75%), the stronger the effect of responding to an invalid cue.

About this implementation

  • In this implementation, there are 100 trials.

  • 75% of the trials have a valid cue (X and GO signal appear in same box)

  • 25% of the trials have an invalid cue (X and GO signal appear in different boxes)

  • The time between the onset of the X cue and the GO signal is 150 milliseconds (i.e., a fraction of a second)

  • Note, at the end of the experiment, you can show your response times and copy and paste them to a local file for your own data analysis.

Run the demo

In this example, you will need to respond to a green circle with the word "go" in it. When it appears in the left yellow box, you press the key "A" on your keyboard. When it appears in the right yellow box, you press the key "L" on your keyboard. In 75% of trials, the "go" circle will be preceded by an "X". You should never respond to the X itself, but wait for the GO signal.

Click here to run a demo of the Posner task

Data output file

In PsyToolkit, the data output file is simply a textfile. The save line of the PsyToolkit experiment script determines what is being saved in the data output file. Typically, for each experimental trial, you would have exactly one line in your text file, and each number/word on that line gives you the information you need for your data analysis, such as the condition, response speed, and whether an error was made.

Meaning of the columns in the output datafile. You need this information for your data analysis.

Colum Meaning

1

cue position (cueleft, cueright)

2

target position (targetleft, targetright)

3

cue validity (cued, uncued)

4

cue validity as number (1=cued, 0=uncued)

5

Response time (ms)

6

Status (1=correct, 2=wrong, 3=timeout)

PsyToolkit code

Click to expand the PsyToolkit script code (part of zip file below) 
# every line starting with # is comment

options
  bitmapdir stimuli    # the folder that contains the stimuli bitmaps

# the following section defines the bitmaps.  the default format for
# bitmaps is "png" if you use png files, you do not need to use the
# extension.

bitmaps
  cuesignal # this refers to the file cuesignal.png
  gosignal
  fixpoint1 # small
  fixpoint2 # medium
  fixpoint3 # large
  box
  instruction
  afterwords
  mistakefeedback

fonts
  arial 20

# the table section contains 8 rows, one for each of the four
# conditions the stuff in quotation marks is human readable
# information

table cueingtable
  "cueleft  targetleft  valid      cued 1"  -200 -200  1
  "cueleft  targetleft  valid      cued 1"  -200 -200  1
  "cueleft  targetleft  valid      cued 1"  -200 -200  1
  "cueright targetright valid      cued 1"   200  200  2
  "cueright targetright valid      cued 1"   200  200  2
  "cueright targetright valid      cued 1"   200  200  2
  "cueleft  targetright invalid  uncued 0"  -200  200  2
  "cueright targetleft  invalid  uncued 0"   200 -200  1

# the task describes exactly one trial. On each each trial, one of the
# rows of the cue table is chosen at random

task cueingtask
  table cueingtable
  keys a l
  delay 500 # time between trials
  show bitmap fixpoint1
  show bitmap box -200 0
  show bitmap box  200 0
  delay 75
  show bitmap fixpoint2
  delay 75
  show bitmap fixpoint3
  delay 75
  clear 4 5
  show bitmap fixpoint2
  delay 75
  clear 6
  show bitmap fixpoint1
  delay 200
  show bitmap cuesignal @2 0 # now show the cue
  delay 75
  clear -1
  delay 75
  show bitmap gosignal @3 0 # show target (go) 700 ms later
  readkey @4 1500
  clear -1
  if STATUS != CORRECT
    show bitmap mistakefeedback 0 200
    delay 2000
    clear -1
  fi
  save @1 RT STATUS # this saves the data to an output file

block cueingblock
  message instruction
  tasklist
    cueingtask 100 # do the task 100 times
  end
  bitmap afterwords
  wait_for_key
  feedback
    text align left
    set &RTvalid   mean c6 ; select c7 == 1 && c5 == 1
    set &RTinvalid mean c6 ; select c7 == 1 && c5 == 0
    text -300 0 "Response time (ms)"
    text -300 50 &RTvalid    ; prefix "Valid cue conditions: "   ; postfix " ms"
    text -300 100 &RTinvalid ; prefix "Invalid cue conditions: " ; postfix " ms"
    text -300 250 "Press space bar to continue"
  end

Download

If you have a PsyToolkit account, you can upload the zipfile directly to your PsyToolkit account. Watch a video on how to do that. If you want to upload the zipfile into your PsyToolkit account, make sure the file is not automatically uncompressed (some browsers, especially Mac Safari, by default uncompress zip files). Read here how to easily deal with this.

Further reading

  • Chun, M. M. (2000). Contextual cueing of visual attention. Trends in Cognitive Sciences, 4, 170-178.

  • Posner, M.I. (1980). Orienting of attention. Quarterly Journal of Experimental Psychology, 3, 3-25.