Dot Task

Dot Task

This is how the stimuli appear on screen:             

The stimuli are 150 static pictures with the arrays of yellow and blue dots varying between 5 and 21 dots of each colour and ratios of the arrays in the two colours between 1:3 and  6:7. The presentation order is the same for all participants (please see attached stimuli list arranged in presentation order with the ratios between the arrays of yellow and blue dots). The stimulus flashes on the screen for 400 ms, maximum response time is 8 sec. If no answer is given during this time the answer is recorded as wrong and a message appears on the screen to encourage pressing the space bar to see the next trial. The message disappeared after 20 sec. and the next trial is displayed only after press of the space-bar. There is a practice trial, with two items and an option to repeat the practice. The task is divided in blocks of 50 trials.  At the end of each block is possible to take a break and resume the test later (come-back button). The test records accuracy and reaction time on correct trials. The measure of the task is the Weber Fraction.

Stimuli and parameters for this task have been provided by the author of the task , Justin Halberda. The task and the method to calculate the Weber fraction are described in the paper:

Halberda, J., Mazzocco, M., & Feigenson, L. (2008). Individual differences in nonverbal estimation ability predict maths achievement. Nature, 455,665-668.

1.      The test should not be allowed to restart (if refresh is pressed on the web browser).

2.      a “come back later” option is shown  between successive items.

3.      No discontinue or branching rules

4.      All pictures to have a fixed size, independent of the browser window size

5.      Each item is to have a fixed timeout for response: 10 seconds.  If a child times out on an item, this will be coded separately in the item response (e.g. 1=blue, 2= yellow, 3=timed out).

Item no.	Yellow dots	Blue dots	Correct response	Image
1	16	5	Y
2	17	13	Y
3	14	18	B
4	7	5	Y
5	13	16	B
6	14	17	B
7	18	21	B
8	19	6	Y
9	16	13	Y
10	6	15	B
11	17	13	Y
12	12	19	B
13	20	17	Y
14	6	17	B
15	16	5	Y
16	15	19	B
17	9	11	B
18	13	10	Y
19	20	6	Y
20	17	14	Y
21	11	15	B
22	14	17	B
23	9	11	B
24	19	10	Y
25	15	13	Y
26	9	11	B
27	20	17	Y
28	5	14	B
29	7	16	B
30	19	15	Y
31	11	13	B
32	9	20	B
33	19	16	Y
34	17	12	Y
35	20	17	Y
36	11	13	B
37	10	13	B
38	7	13	B
39	21	8	Y
40	15	8	Y
41	11	9	Y
42	8	19	B
43	13	11	Y
44	21	9	Y
45	14	17	B
46	15	11	Y
47	13	15	B
48	5	9	B
49	9	11	B
50	20	17	Y
51	14	18	B
52	14	17	B
53	13	17	B
54	20	14	Y
55	17	11	Y
56	13	15	B
57	13	15	B
58	13	15	B
59	14	10	Y
60	17	21	B
61	15	19	B
62	11	9	Y
63	18	14	Y
64	10	13	B
65	13	15	B
66	17	13	Y
67	17	9	Y
68	17	14	Y
69	9	13	B
70	7	13	B
71	17	20	B
72	20	17	Y
73	5	7	B
74	19	14	Y
75	13	15	B
76	13	15	B
77	16	9	Y
78	10	7	Y
79	17	14	Y
80	16	21	B
81	13	16	B
82	8	13	B
83	21	15	Y
84	18	13	Y
85	15	13	Y
86	16	21	B
87	11	14	B
88	14	19	B
89	7	5	Y
90	20	17	Y
91	13	17	B
92	19	16	Y
93	14	17	B
94	21	17	Y
95	18	14	Y
96	19	16	Y
97	17	21	B
98	14	17	B
99	13	15	B
100	17	14	Y
101	18	11	Y
102	11	8	Y
103	17	21	B
104	14	17	B
105	6	11	B
106	19	15	Y
107	20	17	Y
108	11	17	B
109	11	13	B
110	8	14	B
111	21	17	Y
112	21	13	Y
113	14	17	B
114	16	19	B
115	20	12	Y
116	7	5	Y
117	17	14	Y
118	14	19	B
119	13	21	B
120	12	8	Y
121	19	16	Y
122	17	14	Y
123	11	14	B
124	11	13	B
125	8	11	B
126	18	14	Y
127	19	16	Y
128	10	17	B
129	13	11	Y
130	16	11	Y
131	11	15	B
132	11	13	B
133	16	19	B
134	14	11	Y
135	11	13	B
136	17	20	B
137	17	20	B
138	17	12	Y
139	19	15	Y
140	11	14	B
141	14	18	B
142	19	14	Y
143	14	11	Y
144	8	11	B
145	10	14	B
146	16	21	B
147	21	15	Y
148	20	17	Y
149	18	14	Y
150	14	18	B