Final answer:
The avoidant attachment style is marked by individuals being less invested in relationships and more likely to engage in one-night stands.
Step-by-step explanation:
The adult attachment style marked by individuals being less invested in relationships and more likely to engage in one-night stands is avoidant.
With avoidant attachment, the person tends to be unresponsive to their partner, do not use their partner as a secure base, and do not mind if their partner leaves. They may also have a dismissive attitude towards relationships and prefer independence over emotional intimacy. This attachment style is often associated with a caregiver who was insensitive and inattentive to the individual's needs during their childhood.