> They can transmit thoughts directly into your head... via a computer monitor.

> They call it a "a brain-to-brain interface", doesn't that imply one brain is wired directly to another electrically?

The actual paper summary is better:

> Two of the three subjects are "Senders" whose brain signals are decoded using real-time EEG data analysis to extract decisions about whether to rotate a block in a Tetris-like game before it is dropped to fill a line. The Senders' decisions are transmitted via the Internet to the brain of a third subject, the "Receiver," who cannot see the game screen. The decisions are delivered to the Receiver's brain via magnetic stimulation of the occipital cortex.

https://arxiv.org/abs/1809.08632

I don't think "a brain-to-brain interface" implies wiring the brains together at all. To me it means transmitting information that bypasses the traditional human communication channels - and this certainly does because it's read via the EEGs and then sent to the reciever via magnetic stimulation.

There is no information sent between people via the screen. The senders see the full game, and send their decision via magnetic stimulation to the receiver.

The "flashing lights" are ONLY seen by the senders, and used to stimulate the senders brains to send signals that can be read by the EEG. From the paper:

Senders focused their attention on a “Yes” LED light flashing at 17 Hz placed on the left side of their computer screen; to
convey a "Do Not Rotate" decision, they focused on the “No” LED light flashing at 15 Hz placed on the right side. These LEDs
are depicted as circles attached to the screens in Figure 1. The cursor position provided real-time visual feedback to the Senders.
The direction of movement of the cursor was determined by comparing the EEG power at 17 Hz versus 15 Hz, with a higher
power at 17 Hz over that at 15 Hz moving the cursor towards the left side near the “Yes” LED, and vice-versa for the "No"
LED

The decisions of the two Senders were sent to the Receiver’s computer through a TCP/IP network and were further translated
into two pulses of transcranial magentic stimulation (TMS) delivered sequentially to the occipital cortex of the Receiver. Each
TMS pulse lasted 1 ms. An eight-second delay was enforced between the two pulses to remain within the strictest safety
guidelines of TMS stimulation29. The intensity of the stimulation was set above or below the threshold at which the Receiver
could perceive a flash of light known as a phosphene: a “Yes” response was translated to an intensity above the threshold, and
“No” was translated to an intensity below the threshold. During each round of trials, the Receiver always received the decision
from one Sender first, then the other. The screen the Receiver saw also had visual prompts to remind them whose decision
the current TMS stimulation was conveying. Receivers made their decision based on whether a phosphene was perceived and
conveyed their decision (rotate or do not rotate) to the game using the same SSVEP-based procedure used by both Senders.
After the game state was updated, the trial moved into the second round and the above process was repeated.

So there was no physical light flash for the receiver - their brain was just stimulated so they would perceive one.