Romantic Love + Reward / Motivation Systems

This fMRI study found that when people thought of or looked at their beloved, brain areas in the dopaminergic reward pathways (specifically the ventral tegmental area [VTA] and the caudate nucleus) were active. PubMed+2PMC+2
The authors concluded that “romantic love” functions as a motivation system, distinct from just sexual drive, and shares biobehavioural similarity with mammalian attraction systems. PubMed
Key takeaway: Early-stage intense romantic love engages the brain’s reward/motivation circuitry — which can create elevated emotional states, strong attachment, reduced impartiality.

This review describes how attraction, lust, attachment involve distinct but interlinked brain circuits and neurotransmitters: dopamine, norepinephrine, cortisol, serotonin, with key nuclei like the nucleus accumbens and VTA. PMC+1
Example: The nucleus accumbens (a core reward node) is engaged when one experiences romantic attachment.
Key takeaway: The brain chemical state in love overlaps with reward/addiction pathways — meaning people in that state might be less critically vigilant.

2. Trust / Trustworthiness + Brain Mechanisms

The study used fMRI to show that brain signals in the posterior cingulate cortex (PCC), dorsolateral prefrontal cortex (DLPFC) and intraparietal sulcus (IPS) represent impressions of honesty/trustworthiness. Nature
They found that stronger connectivity between the ventromedial prefrontal cortex (VMPFC) and temporoparietal junction (TPJ) during honesty encoding predicted higher trust later. Nature
Key takeaway: The brain forms internal representations of whether someone is trustworthy, and these representations influence future trusting behavior. Thus, trust is not just a social/emotional phenomenon but neuro-cognitive.

This study examined brain responses to trust violations (i.e., when someone fails your trust). They found differential activations when participants experienced trust being broken. IAAP Journals
Such breaches of trust engage brain areas associated with social cognition, emotional regulation, and possibly error/violation monitoring.
Key takeaway: When trust is violated, the brain reacts in ways analogous to error or conflict detection — meaning relational betrayal is processed neurologically, not just emotionally.

Putting it together:

When someone enters a relationship rapidly, evokes emotional attachment early, they may be leveraging the reward/motivation circuits in your brain (as per the romantic-love research) to build influence and reduce your inner vigilance.
Meanwhile, if they present themselves as honest/trustworthy (asset-questions, “I’m vulnerable”, “we’re partners”), they’re engaging your brain’s trust-systems (similar to the honesty/trustworthiness study). Your brain builds a “trust map” of them.
Once trust is established, the manipulator can exploit it (money/resource asks). The neuroscience of trust violation shows that when the trust is broken, the brain processes it as a fundamental error/conflict, which explains why you feel shock, guilt, confusion.
In short: reward system + trust system = vulnerability window. When someone taps both, the risk of exploitation is high.