Table 1 Results of the content validity indexes for the SAS questionnaire

Daily life disturbance (q1-q5)

Missing planned work due to smartphone use

1

1

1

1

Having a hard time concentrating in class, while doing assignments, or while working due to smartphone use

0.8

0.8

0.8

0.8

Experiencing lightheadedness or blurred vision due to excessive smartphone use

0.8

1

1

1

Feeling pain in the wrists or at the back of the neck while using a smartphone

1

1

1

1

Feeling tired and lacking adequate sleep due to excessive smartphone use

1

1

1

1

Positive anticipation (q6-q13)

Feeling calm or cozy while using a smartphone

0.8

1

1

1

Feeling pleasant or excited while using a smartphone

0.8

1

1

1

Feeling confident while using a smartphone

0.8

1

0.6

1

Being able to get rid of stress with a smartphone

0.8

1

0.8

1

There is nothing more fun to do than using my smartphone.

0.8

1

1

1

My life would be empty without my smartphone.

0.8

1

1

1

Feeling most liberal while using a smartphone

0.6

0.8

1

1

Using a smartphone is the most fun thing to do.

1

1

1

1

Withdrawal (q14-q19)

Won’t be able to stand not having a smartphone

0.8

1

0.8

1

Feeling impatient and fretful when I am not holding my smartphone

0.8

1

1

1

Having my smartphone in my mind even when I am not using it

0.8

0.8

0.8

1

I will never give up using my smartphone even when my daily life is already greatly affected by it.

1

0.8

1

0.8

Getting irritated when bothered while using my smartphone

0.6

1

0.8

1

Bringing my smartphone to the toilet even when I am in a hurry to get there

0.8

0.8

0.8

1

Cyberspace oriented relationship (q20-q26)

Feeling great meeting more people via smartphone use

0.6

0.8

0.8

1

Feeling that my relationships with my smartphone buddies are more intimate than my relationships with my real-life friends

0.6

0.8

0.8

1

Not being able to use my smartphone would be as painful as losing a friend.

0.8

1

1

1

Feeling that my smartphone buddies understand me better than my real-life friends

0.8

1

0.8

1

Constantly checking my smartphone so as not to miss conversations between other people on Telegram or Instagram

1

1

1

1

Checking SNS (Social Networking Service) sites like Telegram or Instagram right after waking up

1

1

1

1

Preferring talking with my smartphone buddies to hanging out with my real-life friends or with the other members of my family

1

0.8

1

1

Overuse (q27-q30)

Preferring searching from my smartphone to asking other people

0.8

1

0.8

1

My fully charged battery does not last for one whole day.

0.8

1

1

1

Using my smartphone longer than I had intended

0.8

0.8

0.8

1

Feeling the urge to use my smartphone again right after I stopped using it

1

1

0.8

1

Tolerance (q31-q33)

Having tried time and again to shorten my smartphone use time, but failing all the time

1

1

1

1

Always thinking that I should shorten my smartphone use time

1

1

1

1

The people around me tell me that I use my smartphone too much.

1

1

1

1