Description of Test
The test consists of a series of pictures of recognisable objects or scenes, each with an essential detail omitted from the picture. (The pictures are shown in a table below.) The twin is asked to click on the relevant part of the picture on screen, to identify the part that is missing. There is a time limit of 20 seconds for each picture (shown pictorially by a moving time bar on screen). If 20 seconds passes before the twin has clicked on the picture, this is treated as an incorrect response (zero score), and then the twin is shown a prompt asking them to continue with the next picture.
In order to determine whether a given click corresponds to a correct or an incorrect response, each picture is divided into a rectangular grid. Each cell of the grid is numbered. When a twin clicks on the picture, the relevant grid number is recorded as the item response. The grid is depicted in the table of items below; the correct grid number(s) for each item are also shown in the table.
There are 30 main picture items, plus one initial 'practice' item which contributes to the branching but not to the test score. A twin taking the test may be presented with fewer than 30 items, because of the branching and discontinue rules, which are described below.
Test Rules
- Scoring
For each question, a correct response is given a score of 1, and an incorrect response is given a score of 0. Correct and incorrect responses are based on grid numbers corresponding to where each picture was clicked (see table of items below). The maximum total score for the test is 30 (not including the practice item). - Branching rules
- Start with the practice item p1, and proceed to item 5.
- If both the practice item and item 5 are correct, give credit for items 1-4 (as though they had been answered correctly, gaining a score of 1 for each item), then proceed upwards from item 6.
- If either the practice item or item 5 is incorrect (scoring 0),
attempt the lower items (1-4) in reverse order. Then:
- If any two successive items are correct (e.g. 4 and 3), then give credit for any of items 1-4 not yet attempted; then proceed upwards from item 6. Note that if either the practice item or item 5 is correct, while the other is incorrect, and this is followed by a correct answer for item 4, then this results in an upward branch to item 6 (the practice item and item 4 are treated as successive items for this rule, as are item 5 and item 4).
- If no two successive items are correct, the test ends after item 1 has been attempted.
- Discontinue rules
Discontinue the test after five scores of zero in any five consecutive items. This rule applied throughout the test after five or more items had been attempted. - Timeout rule
A timeout of 20 seconds applies to each item. After 20 seconds with no response, the item is forfeited with zero score, and a "next item" screen appears. On resuming the test, the twin is taken to the next item in sequence as described above.
Item Variables
The item variables relating to the Picture Completion test, as listed in the table below, were generated automatically by programs on the web server during the course of the test. Note that the dataset only includes data for completed tests. If a twin started the test but left it unfinished, then the data for the test were not used.
In most cases the values of these variables have been left unaltered, although some have been recoded during data cleaning as follows. See the web data cleaning page for further details.
- For timed out items, the item response variable is recoded from missing to -1, and the item answer time is recoded from 20 to missing (item scores are 0)
- For items skipped due to the discontinue rule, the item response variable is recoded from missing to -2, and the item score is recoded from missing to 0.
- For items skipped and credited due to upward branching, the item response variable is recoded from missing to -3 (the item score is already recorded as 1 on the web server).
- For items that crashed or malfunctioned in any way, the item response variable is recoded from missing to -4, and the item score is recoded from missing to 0.
- For twins identified as random responders in this test, the status flag is recoded from 2 to 4, the data flag is recoded from 1 to 0, and all item variables are recoded to missing (test data deleted)
The test start and end dates and times, and item answer and download times, and item orders, have not been retained in the dataset.
Variables | Explanation | Values |
---|---|---|
jpcstat1/2 | Test status: outcome of test | 0=not started, 1=started but not finished, 2=successfully completed, 4=random responses |
jpcdata1/2 | Data flag: is test data present in the dataset? | 0=no, 1=yes |
jpcstdt1/2 | Start date of the test [not in dataset] | Date values |
jpcsttm1/2 | Start time of the test [not in dataset] | Time values |
jpcendd1/2 | End date of the test [not in dataset] | Date values |
jpcendt1/2 | End time of the test [not in dataset] | Time values |
jpcsess1/2 | Number of sessions (at the computer) used by the twin to complete the test. | Integer values of 1 or above |
jpctime1/2 | Time taken to complete the test, in seconds | Integer values (number of seconds) |
jpc01a1/2 through to
jpc30a1/2 (items 1-30), and jpcp1a1/2 (practice item) |
Item response (see table of items below for details) | Integer, representing the number of the grid square clicked. Alternatively, -1=timed out, -2=discontinued, -3=credited due to upward branching, -4=item crashed. |
jpc01s1/2 through to
jpc30s1/2 (items 1-30), and jpcp1s1/2 (practice item) |
Item score (see table of items below for details) | 0=incorrect, 1=correct |
jpc01at1/2 through to
jpc30at1/2 (items 1-30), and jpcp1at1/2 (practice item) |
Answer time: length of time (in seconds) taken by the twin to respond to this item [not in dataset] | Integer values (number of seconds) |
jpc01dt1/2 through to
jpc30dt1/2 (items 1-30), and jpcp1dt1/2 (practice item) |
Download time: length of time (in seconds) between the end of the previous item and the start of this item; time needed to download files for this item [not in dataset] | Integer values (number of seconds) |
jpc01o1/2 through to
jpc30o1/2 (items 1-30), and jpcp1o1/2 (practice item) |
Order or sequence of this item in the test; dependent on the branching path taken by the twin through this test [not in dataset] | Integer values of 1 or above |
Test Items
The numbering of the items, shown in the table below, equates to the numbering used in the item variables. Note that this is not the same as the order in which items were presented to twins in the test (see branching rules above).
item | picture | correct response (missing part) | correct grid number(s) |
---|---|---|---|
(grid) | (the picture is for item 4, but this same grid was used for all items) | (numbers below, in this column, refer to this grid) | |
p1 (practice item) | lead tip of pencil | 73, 74 | |
1 | ear of fox | 27-29, 40 | |
2 | lid flap of box | 14-18, 26-30, 38-42, 50-54, 62-66 | |
3 | whiskers on one side of cat's face | 31, 32 | |
4 | finger nail of little finger | 32 | |
5 | leg of elephant | 75-77, 87-89, 99-101 | |
6 | strap of watch | 92 | |
7 | bottom door hinge | 52, 64, 76, 88, 100 | |
8 | reflection of doll in girl's hand | 40, 52, 64 | |
9 | number 11 on face of clock | 29 | |
10 | handle on second drawer from top | 44, 45 | |
11 | holes in belt | 61-62, 73-74, 86-91 | |
12 | veins in part of the top leaf | 16-17, 27-29 | |
13 | second-bottom step | 56, 66-69, 78-79 | |
14 | eye lashes on one eye | 55, 56 | |
15 | dot on top of right-hand die (there should be 6 dots) | 33 | |
16 | plug hole in bath | 52-55, 64-66 | |
17 | filament of bulb | 30-32, 42-44, 54-56, 66-68 | |
18 | hole in top of whistle | 40-42, 52-56, 67-68 | |
19 | black keys on piano keyboard | 63-70 | |
20 | hinge where scissor blades meet | 66-68 | |
21 | eye brow | 40-42, 53 | |
22 | red liquid in thermometer bulb | 103 | |
23 | slat near top-left of lattice | 7, 17-19, 29-30, 39-41, 50-52, 62-63, 73-74 | |
24 | pith dividing segments in part of orange | 43-45, 55-57 | |
25 | gill of fish | 52-53, 64-65 | |
26 | labels on cans, on top-right shelf | 45-48 | |
27 | cable attached to phone hand set (on either side) | 50-52, 57-58, 62-64, 69-70, 75-76, 81-82 | |
28 | spoke of umbrella | 30, 43, 55-56, 67-68 | |
29 | shadow of tree | 62-64, 73-77, 86-88 | |
30 | eye hole for lace of shoe | 42 |