A method of inducing a Pavlovian association of a scent with sleep initiation, the method comprising: detecting, by a control circuit using at least a physiological sensor, at least a physiological parameter of a user; determining, by the control circuit and as a function of the detected at least a physiological parameter, that the user is entering a hypnagogic state in which the user's entry into a sleep cycle is imminent, wherein the determining comprises: determining that the detected at least a physiological parameter indicates that the user is in a state of pre-sleep relaxation; determining, using a machine-learning algorithm, a pattern associated with the detected at least a physiological parameter; calculating an average time from detection of indication of pre-sleep relaxation to detection of entry into a sleep state associated with the user as a function of the pattern; predicting a user's time of entry into the sleep cycle as the average time after the determined indication of pre-sleep relaxation; and estimating the time of entry into the hypnagogic state as a time point between the indication of pre-sleep relaxation and the predicted time of entry into the sleep cycle; and triggering, by the control circuit and using a scent diffuser controlled by a logic circuit of the control circuit, a release of a scent at the estimated time of entry into the hypnagogic state. detecting, by a control circuit using at least a physiological sensor, at least a physiological parameter of a user; determining, by the control circuit and as a function of the detected at least a physiological parameter, that the user is entering a hypnagogic state in which the user's entry into a sleep cycle is imminent, wherein the determining comprises: determining that the detected at least a physiological parameter indicates that the user is in a state of pre-sleep relaxation; determining, using a machine-learning algorithm, a pattern associated with the detected at least a physiological parameter; calculating an average time from detection of indication of pre-sleep relaxation to detection of entry into a sleep state associated with the user as a function of the pattern; predicting a user's time of entry into the sleep cycle as the average time after the determined indication of pre-sleep relaxation; and estimating the time of entry into the hypnagogic state as a time point between the indication of pre-sleep relaxation and the predicted time of entry into the sleep cycle; and determining that the detected at least a physiological parameter indicates that the user is in a state of pre-sleep relaxation; determining, using a machine-learning algorithm, a pattern associated with the detected at least a physiological parameter; calculating an average time from detection of indication of pre-sleep relaxation to detection of entry into a sleep state associated with the user as a function of the pattern; predicting a user's time of entry into the sleep cycle as the average time after the determined indication of pre-sleep relaxation; and estimating the time of entry into the hypnagogic state as a time point between the indication of pre-sleep relaxation and the predicted time of entry into the sleep cycle; and triggering, by the control circuit and using a scent diffuser controlled by a logic circuit of the control circuit, a release of a scent at the estimated time of entry into the hypnagogic state.