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ROLE OF COGNITIVE EFFORT
381
imagery of high hypnotizable participants was more vivid,
M
= 5.50,
SE
= 0.19, than that of lows,
M
= 4.67,
SE
= 0.20. There were no other
significant effects for vividness.
The analysis of absorption also yielded a significant main effect for
hypnotizability,
F
(1, 44) = 10.14,
p
< .01,
h
2
= .19. As hypothesized, the
imagery of highs was more absorbing,
M
= 5.15,
SE
= 0.19, than that of
lows,
M
= 4.26,
SE
= 0.20. The two other significant effects both
involved suggestion wording: a main effect,
F
(1, 44) = 7.29,
p
= .01,
h
2
=
.14, and a suggestion wording by gender interaction,
F
(1, 44) = 4.45,
p
=
.04,
h
2
= .09. The effortful suggestion wording generally produced
higher absorption,
M
= 4.91,
SE
= .15, than the effortless wording,
M
=
4.51,
SE
= 0.16; however, this difference was stronger for males (4.80
vs. 4.09) than for females (5.01 vs. 4.92).
The analysis of subjective effort again yielded a significant main
effect for hypnotizability,
F
(1, 44) = 9.70,
p
< .01,
h
2
= .18. As hypothe-
sized, the imagery of highs was experienced as less effortful,
M
= 3.02,
SE
= 0.22, than that of lows,
M
= 4.01,
SE
= 0.23. There were no other
significant effects.
The analysis of subjective control yielded three significant effects,
all involving suggestion wording: a main effect,
F
(1, 44) = 13.74,
p
< .01,
h
2
= .24, a suggestion wording by hypnotizability interaction,
F
(1, 44) =
4.34,
p
= .04,
h
2
= .09, and a suggestion wording by gender interaction,
F
(1, 44) = 6.53,
p
= .01,
h
2
= .13. The effortful suggestion wording gener-
ally produced higher subjective control,
M
= 4.24,
SE
= 0.19, than the
effortless wording,
M
= 3.56,
SE
= 0.19; however, this difference was
stronger for highs (4.32 vs. 3.27) than for lows (4.15 vs. 3.85), and for
females (4.33 vs. 3.19) than for males (4.14 vs. 3.93).
In summary, high hypnotizable participants experienced their imag-
ery as more vivid, more absorbing, and less effortful than lows did, sup-
porting our first prediction. Having confirmed these differences, we can
proceed to investigate whether the richer experience of highs is the
result of expending a higher level of underlying cognitive effort.
In comparison to the effects of hypnotizability, the effects of sugges-
tion wording were somewhat sporadic. Relative to the effortless sug-
gestion wording, the effortful wording yielded higher absorption, but
mainly for men, and higher subjective control, but more so for high
hypnotizables and for women. Surprisingly, suggestion wording had
no significant impact on subjective ratings of effort, inconsistent with
our second prediction. However, one of our main themes is that sub-
jective effort may be a poor index of actual cognitive effort; therefore,
let us now turn to the objective index of cognitive effort.
Heart-Rate Change
For each participant, the heart-rate increase for effortless suggestion
wording was obtained by averaging the three heart-rate changes from
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