M ain A n alyses

Target acts produced at first action

In 2 X 3 (age x condition) ANOVAs on the proportion of children’s first acts coded in the category of Target Act, these did not reveal a main effect of age, F (1, 54) = 0.05, p > 0.8,or a main effect of condition, F (2, 54) = 1.35, p > 0.2. Neither was there a significant age x condition interaction, F (2, 54) = 0.16, p > 0.8.

Target acts produced at first and second actions combined

In 2 X 3 (age x condition) ANOVAs on the proportion of children’s first and second actions combined coded in the category of Target Act, these did not yield a main effect of age, F (1, 54) = 0.68, p > 0.4, or a main effect of condition, F (2, 54) = 0.30, p > 0.7. The age x condition interaction was not significant, F (2, 54) = 1.06, p >0.3.

Table 5.1. Means of the proportion of 17- and 39-month-old children’s first actions and combination of first and second actions falling into each of the

Condition Action / age Failed-Attempt (neutral) Mean (SD) Failed-Attempt ( accidentally fa ile d ) Mean (SD) Failed-Attempt ( intentionally fa ile d ) Mean (SD) TA-1®‘ 17-month-old .32 (.14) .24 (.16) .34 (.19) 39-month-old .38 (.29) .22 (.22) .30 (.33) FA-l'^ 17-month-old .06 (.10) .10 (.11) .08 (.10) 39-month-old .30 (.22) .30 (.22) .36 (.26) O A l " 17-month-old .54 (.16) .60 (.23) .58 (.22) 39-month-old .32 (.23) .46 (.19) .34 (.27) NO-1'^ 17-month-old .00 (.00) .00 (.00) .00 (.00) 39-month-old .00 (.00) .00 (.00) .00 (.00) TA (UN)-1'' 17-month-old .02 (.06) .06 (.10) .04 (.08) 39-month-old .00 (.00) .02 (.06) .00 (.00) TA (F)-l'‘ 17-month-old .06 (.10) .00 (.00) .00 (.00) 39-month-old .00 (.00) .00 (.00) .00 (.00) Total 17-month-old 1.00 1.00 1.00 39-month-old 1.00 1.00 1.00

Note. TA-1*‘ = target act produced at first other act produced at first action; N0-1*‘ = target act produced at first action; TA (F)- the object set of box and stick.

action; FA-1*‘ = failed act produced at first action; 0A-1*‘ = = no act produced at first action; TA (UN)-1*‘ = unfinished

Table 5.1. (Continued)

Condition Failed-Attempt Failed-Attempt Failed-Attempt

(neutral) (A ccidentally fa iled ) ( intentionally fa ile d )

Action / age M e a n ( S D ) M e a n ( S D ) M e a n ( S D ) T A -r‘+2"‘* 17-month-old .38 (.15) .42 (.15) .46 (.27) 39-month-old .46 (.30) .30 (.24) .34 (.34) FA-1"‘ + 2““ 17-month-old .10 (.14) .12 (.14) .22 (.20) 39-month-old .50 (.33) .48 (.23) .54 (.33) OT-1®* + 2"“ 17-month-old .78 (.20) .80 (.16) .84 (.13) 39-month-old .38 (.22) .54 (.21) .48 (.29) NO-1®* + 2“** 17-month-old .06 (.13) .00 (.00) .00 (.00) 39-month-old .24 (.28) .10 (.19) .16 (.35) TA (UN)-1®* + 2"“ 17-month-old .06 (.13) .12 (.14) .06 (.10) 39-month-old .00 (.00) .02 (.06) .00 (.00) TA(F)-1®* + 2““ 17-month-old .08 (.10) .02 (.06) .00 (.00) 39-month-old .00 (.00) .00 (.00) .00 (.00) REPEAT 17-month-old .54 (.28) .52 (.21) .42 (.24) 39-month-old .42 (.22) .56 (.26) .48 (.29) Total 17-month-old 2.00 2.00 2.00 39-month-old 2.00 2.00 2.00 TA-20 sec 17-month-old .44 (.13) .50 (.17) .54 (.28) 39-month-old iT< A 1 SI . /^nd ^ _ .52 (.30) .32 (.29) _____ l . T - ’ A .38 (.35)1 S t . , - » n d J

act produced at first and second actions combined; 0A-1*‘ + 2“** = other act produced at first and second actions combined; N0-1*‘+ 2"^ = no act produced at first and second actions combined; TA (UN)-l*‘+2”‘' = unfinished target act produced at first and second actions combined; TA (F)-l*‘ + 2“'* use of a finger to activate the beeper in the object set of box and stick at first and second actions combined; Repeat = a scoring category repeatedly scored at first and second actions; TA-20 sec = target act produced during 20 seconds of the response period.

Target acts produced during 20 seconds o f response period

As in the preceding analyses, there was no main effect of age and main effect of condition on the proportion of children’s acts produced in the 20-second response period coded in the category of Target Act, F (1, 54) = 1.62, p > 0.2, and F (2, 54) = 0.37, p > 0.2, respectively. Also, there was no significant age x condition interaction, F (2, 54) = 1.51, p > 0.3.

Failed acts produced at first action

There was a main effect of age on the proportion of children’s first actions coded in the category of Failed Act, F (1, 54) = 26.75, p < 0.001. There was no main effect of condition, F (2, 54) = 0.25, p > 0.7, and no significant age x condition interaction, F (2, 54) = 0.25, p > 0.7. Figure 5.1 shows that collapsing over

conditions, the 39-month-olds were more likely to reproduce the demonstrated failed attempts as their first acts than the 17-month-olds.

I

Age group

□ 17-month-old

O 39-month-old FA (neutral) FA (by accident) FA (by intention)

Experimental condition

Note. FA = Failed-Attempt.

Figure 5.1. Means and 95% Cl of the proportion of 17- and 39-month-old children’s first actions coded in the category of Failed Action (FA-1®‘) as a function of age.

Failed acts produced at first and second actions combined

There was a main effect of age on the proportion of children’s first and second actions combined coded in the category of Failed Act, F (1, 54) = 33.31, p < 0.001. There was no main effect of condition, F (2, 54) = 0.73, p > 0.7, and no significant age X condition interaction, F (2, 54) = 0.14, p > 0.8. The results were the same as the analyses of such acts produced as the children’s first acts. Figure 5.2 shows that collapsing over conditions, the 39-month-olds were more likely to reproduce the demonstrated failed attempts as their first and second actions combined than the 17- month-olds.

5.3.2. Su bsidiary analyses

Other acts produced at first action

There was a main effect of age on the proportion of children’s first acts coded in the category of Other Act, F (1, 54) = 12.35, p < 0.001. There was no main effect of condition, F (2, 54) = 1.08, p > 0.3, and no significant age x condition interaction, F (2, 54) = 0.29, p > 0.7. Figure 5.3 shows that collapsing over conditions, the 17- month-olds were more likely to produce other acts as their first acts than the 39- month-olds.

Object parts children first touched

Table 5.2 displays the means of the proportion of object parts that children first touched across the five sets of objects. The data are presented according to whether the children touched the same parts of the object sets as the experimenter, or different parts of the object sets from the experimenter, or touched more than one part at a time, or did not touch the object sets at all. In 2 x 3 (age x condition) ANOVAs on the proportion of first-touched object parts which were the same as those the experimenter first touched, these yielded a main effect of age, F (1, 54) = 7.31, p < 0.009. There was no main effect of condition, F (2, 54) = 0.63, p > 0.6, and no significant age x condition interaction, F (2, 54) = 0.80, p > 0.4. Collapsing over conditions, the 39-month-olds started by taking hold of the same parts of the objects as the experimenter more frequently than the 17-month-olds.

• f i

Age group

□ 17-month-old

O 39-month-old FA (neutral) FA (by accident) FA (by intention)

Experimental condition

Note. FA = Failed-Attempt.

Figure 5.2. Means and 95% Cl of the proportion of 17- and 39-month-old children’s first and second actions combined coded in the category of Failed Act (FA-1^^ + 2“**) as a function of age.

• f i

Age group

□ 17-month-old

O 39-month-old FA (neutral) FA (by accident) FA (by intention)

Experimental condition

Note. FA = Failed Attempt.

Figure 5.3. Means and 95% Cl of the proportion of 17- and 39-month-old

children’s first actions coded in the scoring category of Other Action (OA-l*‘) as a function of age.