I would like to know if Android devices make active or passive scan when looking for the AP to connect. I've already made a test using Wireshark and wifi sniffer and it seems that while an iPhone sends Probe Request frames to discover available APs (active scan), my Android device sometimes sends Probe Request frame, but most of the times it does not send Probe Request frames at all, but waits for the AP to send a Beacon frame (passive scan).
I've been looking for some official info/documentation concerning this topic, but haven't found anything useful yet. I would be very grateful if someone could provide me with the answer to this question.