Introduction

Visual search is about how we search and find objects using our vision. Research on searching for items in a search display goes back to the work of Anne Treisman in the late 1970s. One of the important ideas of searching for features with specific items (e.g., searching for a green round bottle among a large collection of bottles) is that this cannot be done in parallel; hence, the more items there are to search through, the longer it takes.

Searching for specific combinations of features in items (e.g., the ROUND GREEN bottle amongst bottles of all sorts of colors and shapes) is known as conjunctive search. The increase in conjunctive search time due to the numbers present is known as the search slope.

This Scholarpedia page has good background information. It is curated by well know visual search researcher Jeremy Wolfe.

About this implementation

  • Note, 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 need to respond to the letter T, but only if it is in it’s regular upright position and only if it is orange. You respond with the space bar (and do not do anything if no T is present). There are 50 search displays, and the task takes around 5 minutes to complete. In each display, there are 5, 10, 15, or 20 items. Search time increases with large numbers of items on the screen.

Click here to run a demo of the visual search 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

blockname

2

the stimulus display number (that is, the line number of the display as defined in the table)

3

distractor present? 1=yes, 0=no

4

number of distractors

5

status (1=correct, 2=error, 3=too slow)

6

the response time (ms)

PsyToolkit code

Click to expand the PsyToolkit script code (part of zip file below) 
options
  bitmapdir stimuli

bitmaps
  aims
  target
  distractor1
  distractor2
  empty
  mask1
  mask2
  fixpoint
  frame
  therewasnone
  toolate

fonts
  arial 20

table general # this table is created with search.r
  include search_table.txt

task search
  table general
  keys space
  show bitmap fixpoint # 1
  delay 100
  clear 1
  delay 400
    show bitmap @4 @5 @6 # 2
    show bitmap @7 @8 @9 # 3
    show bitmap @10 @11 @12 # 4
    show bitmap @13 @14 @15 # 5
    show bitmap @16 @17 @18 # 6
    show bitmap @19 @20 @21 # 7
    show bitmap @22 @23 @24 # 8
    show bitmap @25 @26 @27 # 9
    show bitmap @28 @29 @30 # 10
    show bitmap @31 @32 @33 # 11
    show bitmap @34 @35 @36 # 12
    show bitmap @37 @38 @39 # 13
    show bitmap @40 @41 @42 # 14
    show bitmap @43 @44 @45 # 15
    show bitmap @46 @47 @48 # 16
    show bitmap @49 @50 @51 # 17
    show bitmap @52 @53 @54 # 18
    show bitmap @55 @56 @57 # 19
    show bitmap @58 @59 @60 # 20
    show bitmap @61 @62 @63 # 21
  readkey 1 4000
  set &x 0 # this means, there was no error
  if STATUS == CORRECT # means space pressed, might be incorrect though
    if @2 == 0 # there was none
      show bitmap therewasnone 0 200 # 22
      delay 2000
      clear 22
      delay 500
      show bitmap mask1 # 23
      delay 100
      show bitmap mask2 # 24
      delay 100
      clear range 1 24
      set &x 1
    fi
  fi
  if STATUS == TIMEOUT # means space pressed, might be incorrect though
    if @2 == 1 # there was one, now show it on yellow background
      show bitmap toolate 0 200 # 22
      show bitmap frame  @5 @6  # 23
      show bitmap target @5 @6  # 24
      delay 2000
      clear 22
      delay 500
      show bitmap mask1 # 25
      delay 100
      show bitmap mask2 # 26
      delay 100
      clear range 1 26
      set &x 1
    fi
  fi
  if &x == 0
    show bitmap mask1 # 22
    delay 100
    show bitmap mask2 # 23
    delay 100
    clear range 1 23
  fi
  delay 1000
  save BLOCKNAME @1 @2 @3 STATUS RT

#----------------------------------------------------------------------
# blocks
# ----------------------------------------------------------------------

message aims

block block1
  tasklist
    search 50 all_before_repeat
  end
  feedback
    set &RTfive    mean c6 ; select c3 == 1 && c5 ==1 && c4 == 5  
    set &RTten     mean c6 ; select c3 == 1 && c5 ==1 && c4 == 10 
    set &RTfifteen mean c6 ; select c3 == 1 && c5 ==1 && c4 == 15 
    set &RTtwenty  mean c6 ; select c3 == 1 && c5 ==1 && c4 == 20 
    text 0 0 "Search time (ms)"
    text 0  50 &RTfive    ; prefix "With  5 items: " ; postfix " ms"
    text 0 100 &RTten     ; prefix "With 10 items: " ; postfix " ms"
    text 0 150 &RTfifteen ; prefix "With 15 items: " ; postfix " ms"
    text 0 200 &RTtwenty  ; prefix "With 20 items: " ; postfix " ms"
    text 0 250 "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

  • Treisman, A. (1977). Focussed attention in the perception and retrieval of multidimensional stimuli. Perception and Psychophysics, 9, 40-50.

  • Treisman, A., & Gelade, G. (1980). A feature integration theory of attention. Cognitive Psychology, 12, 97-136.