Researchers examined the mental activity of 114 volunteers while they tweeted on phones, tablets and laptops, using a technique called steady-state topography.
They found markedly higher responses than the norm in the three areas which correspond to emotional arousal, feelings of personal relevance, and memory.
Emotional arousal is linked to sites in the back right half of the brain, and the study used activity at the right parieto-temporal site to assess the intensity of emotions elicited by the service, the Guardian reported.
"The way that messages are delivered drives a strong emotional response," said Heather Armstrong, chief executive of market research firm Neuro Insight, which carried out the study.
"It's very short and sharp, it's very immediate, and it's appearing in your own context," said Armstrong.
Twitter scores quite so highly because "people are seeing stuff in a context which is immensely personally relevant," said Armstrong.