Some studies have demonstrated an improved selective attention of Internet Addicts compared with normal people. However, most of these studies were done based on the single-task experimental paradigm, in which participants were required to perform only a visual search task. This single-task paradigm has neglected the inseparable relationship between the visual working memory and selective attention. In the present study, we employed a dual-task paradigm that required the participants to perform a visual search task while keeping an object in working memory. The purpose of this study was to exam the differences of attentional capture between Internet Addicts and normal people.

In our experiments, participants were instructed to remember a color object as the target item, and then to seek the target among five distractors. Experiment 1 used a single distractor under three conditions: (1) the distractor matched with the target item in color; (2) the distractor differed from the target item in color; (3) the distractor had no color. There were 16 participants in the Internet addition group (13 male, 18~22 years old, M = 19.25, SD = 0.86) and 24 participants in the control group (18 male, 18~20 years old, M = 18.96, SD = 0.84). Experiment 2 used multiple distractors under two conditions: (1) three (out of five) distractors matched with the target item in color and shape (matching trials); (2) all five distractors differed from the target item in color and shape (control trials). The proportion (20% or 80%) of matching trials was varied across different experimental groups to induce different levels of inhibition motivation. There were 31 participants (21 male, 18~22 years old, M = 19.35, SD = 1.05) in the Internet addition group and 32 participants (22 male, 18~20 years old, M = 19.56, SD = 1.05) in the control group.

Repeated-measures ANOVA was used to analyze the RTs. In both experiments, participants in the Internet addition group responded faster than those in the control group. There was no evidence for a speed-accuracy trade-off in both groups. When there was only one distractor in the search task (Experiment 1), the distractor would capture the attention of participants in the control group under all conditions, but would not capture the attention of participants in the Internet addition group. When there were multiple distractors in the search task (Experiment 2), the attentional capture effects differed by the level of inhibition motivation. At a low level of inhibition motivation, search RTs were shorter in matching trials than in control trials for both groups, demonstrating a classical memory-based attention capture effect induced by memory-matching distractors. This effect was smaller in the Internet addition group. At a high level of inhibition motivation, search RTs were shorter in matching trials than in control trials, suggesting that there was a memory-based attention inhibition affected by top-down control. There was no difference in the attention inhibition effect between the two groups.