Participants affected by obesity (the level of body mass index (BMI) higher or equal to 30).

Not-hospitalized participants with a healthy weight

It is a 2-day paradigm. Participants will undergo an auditory fear conditioning task in 3 phases: (1) pre-conditioning habituation, (2) unconditioned stimulus (US) calibration, where USs will be delivered to set the individual stimulation intensity threshold, and (3) fear conditioning, in which participants will be exposed to the conditioned stimulus (CS) associated with the US with an 80% pairing rate. 24 hours later, the (1) implicit recognition of the CS and novel stimuli (NSs), and the (2) explicit recognition, through an alternative forced-choice task will be assessed. Also, (3) the perceptual discrimination (among the CS and NSs) will be tested.

Event-related skin conductance responses (SCRs) will be collected as an implicit index of defensive fear responses, while the accuracy in detecting and discriminating the CS from NSs as the explicit index. Psychological questionnaires about anxiety symptoms will be also administered.

The event-related skin conductance responses (SCRs) in the case of the CS will be measured. This will represent the implicit index.

Level of accuracy (in %) in recognizing and discriminating the CS from NS will be computed. This will represent the explicit index.