Dot-probe task performance split by levels of urges to be online and internet use groups (All the raw data are presented in Table 3.6) internet use groups (All the raw data are presented in Table 3.6)

Attentional bias as assessed with eye movement data (fixation duration-direction of initial fixation)

Fixation Duration

A 2 x 4 x 2 mixed-way ANOVA with image type (internet versus control) as a within factor and internet use group (problematic, high engagers, moderate and non-problematic internet users) and levels of urges to be online (internet users with higher levels of urges to be online, internet users with lower levels of urges to be online) as between factors was

Internet use group

Problematic internet users

High engagers internet users

Moderate internet users

Non-problematic internet users Levels of

urges to be online

High Low High Low High Low High Low

Percentages 70.6% 29.4% 64.3% 35.7% 45% 55% 23.5% 76.5%

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performed. There were significant interactions between image type and levels of urges to be online, F(1, 60) = 7.51, p = .008 ^Ƞp2 .11, and internet use group with levels of urges to be online, F(3, 60) = 3.46, p = .022 Ƞp² .15. The main effects of image, F(1, 60) = 1.44, p = .41, internet use group, F(3, 60) = 1.21, p = .31, levels of urges to be online group, F(1, 60)

= 0.14, p = .71 and the interactions between image type and internet use group, F(3, 60) = 0.21, p = .89 and image type, internet use group and levels of urges to be online group, F(3, 60) = 0.48, p = .70 were not significant.

In order to investigate the significant interaction between image type and levels of urges to be online a 2 x 2 mixed-way ANOVA was performed with image type (internet versus control) as a within factor and levels of urges to be online (internet users with higher levels of urges to be online, internet users with lower levels of urges to be online) as a between factor. There was a significant interaction between image type and levels of urges to be online, F(1, 66) = 9.31, p = .003; Ƞp² .12. However, the main effect of image type was not significant, F(1, 66) = 1.24, p = .27. The group of internet users with higher levels of urges to be online spent significantly more time fixating on the internet compared to the control images, t(33) = 2.46, p = .019, d = .86, 95% CI [15.55, 163.85]. The group of internet users with lower levels of urges to be online spent more time fixating on the control compared to the internet images and this difference approached significance, t(33) = -1.8, p = .078, d = .63, 95% CI [-88.55, 5.02]. Group comparisons revealed that internet users with higher levels of urges to be online spent significantly more time fixating on the internet images compared to internet users with lower levels urges to be online, t(66) = -2.51, p = .0015, d = .62, 95%

CI [30.74, 15.67]. Moreover, internet users with lower levels of urges to be online showed a tendency of fixating more on the control images compared to internet users with higher levels of urges to be online, t(66) = -1.76, p =.082, d = .43, 95% CI [-116.01, 7.19] (Figure 6).

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Figure 3.10 Mean gaze dwell time (in milliseconds) on internet and control images, shown separately for internet users with higher and lower levels of urges to be online. Error bars represent standard error of the means.

Furthermore, in order to investigate the significant interaction between internet use groups and levels of urges to be online a 2 x 2 mixed-way ANOVA was performed with image type (internet versus control) as a within factor and levels of urges to be online (internet users with higher levels of urges to be online, internet users with lower levels of urges to be online) as a between factor, for each internet users group (problematic, high engagers, moderate and non-problematic internet users). For the problematic internet users there was a significant effect of levels of urges to be online, F(1, 15) = 5.78, p = .03; Ƞp²

.28. The problematic internet users with higher levels of urges to be online fixated significantly longer on the internet images compared to problematic internet users with lower levels of urges to be online, t(15) =2.65, p =.018, d =1.37, 95% CI [88.99, 46.30]. Moreover, there was a trend for problematic internet users with higher levels of urges to be online to fixate more on the internet compared to control images, although this difference failed to reached significance, t(11) =1.82, p =.096. However, the main effect of image type, F(1, 15)

┌───── * ─────┐

*

153

= .29, p = .60, and the interaction with image type and levels of urges to be online group F(1, 15) = .29, p = .60, were not significant as well as the main effects and interactions for the high engagers, moderate and non-problematic internet users (Figure 3.11).

Figure 3.11 Mean gaze dwell time on internet images, shown separately for internet users with higher and lower levels of urges to be online for each internet use group (problematic, high engagers, moderate and non-problematic internet users) with CI error bars.

Direction of initial fixation

Overall, the results revealed no direction of initial fixation bias for internet users with higher levels of urges to be online, t(32) = -.06, p = .948, or for internet users with lower levels of urges to be online, t(33) = -1.04, p = .306.

Attentional bias as assessed with manual reaction times to probes

*

154

A 2 x 2 x 4 mixed-way ANOVA was performed with probe condition (probe in the same congruent versus different incongruent location with internet images) as a within factor and internet use groups (problematic, high engagers, moderate and non-problematic internet users) and levels of urges to be online (internet users with higher levels of urges to be online, internet users with lower levels of urges to be online) as between factors. The main effects probe condition, F(1, 59) = 2.03, p = .16, internet use group, F(3, 59) = 0.91, p = .44, levels of urges to be online group, F(1, 59) = 2.3, p = .13 and the interactions between probe condition and internet use group, F(3, 59) = 0.72, p = .55, probe condition and levels of urges to be online group, F(3, 59) = 0.58, p = .45, and probe condition, internet use group and levels of urges to be online group, F(3, 59) = 0.52, p = .67 were not significant.

3.4.8 Pleasantness rating task: stimulus valence measures

A 2 x 2 x 4 mixed-way ANOVA was conducted with image type (internet versus control) as a within factor and internet use groups (problematic, high engagers, moderate and non-problematic internet users) and levels of urges to be online (internet users with higher levels of urges to be online, internet users with lower levels of urges to be online) as between factors. There was a significant main effect of image type, F(1, 60) = 84.45, p = .001, Ƞp²

.58, and internet use group with image type interaction, F(3, 60) = 2.82, p = .046, Ƞp²

.12. Overall, the participants rated internet images as more pleasant than control images, t(67) = 9.4, p = .0001, d = 2.29, 95% CI [0.75, 1.15]. See section 3.4.3 for further analysis.

The main effects of internet use group, F(3, 60) = 1.04, p = .38, levels of urges to be online group, F(1, 60) = .63, p = .43 and the interactions between image type and levels of urges to be online group, F(3, 60) = 0.78, p = .38, image type, internet use group and levels of urges to be online group, F(3, 60) = 0.20, p = .99, and internet use group and levels of urges to be online group, F(3, 60) = 2.17, p = .101 were not significant.

3.4.9 Supplementary analysis for computer condition split by levels of urges