Dysphoric milk ejection reflex sense of depression and this feeling can range from mild homesickness or wistfulness to more intense feelings of hopelessness and self-loathing. Similarly, anxiety may range from restlessness to more intense panic and dread. Anger, the least likely of the three, may range from tension and agitation to more intense feelings of hostility and aggression. The mechanism is not clear. In a mother with D-MER, dopamine may fall inappropriately with milk release, causing the negative feelings. Among the hormones involved in milk production and release are oxytocin, prolactin, and dopamine. Oxytocin, released in pulsatile "spikes" from the posterior pituitary in response
Psychological refractory period caffeine intake have also been investigated. PRP is a product of the psychological refractory period paradigm, a paradigm in which two different stimuli are presented in rapid succession, each requiring a fast response. Stimulus onset asynchrony, the time that lapses between the presentations of the two stimuli, acts as the "independent variable" in this paradigm, and the reaction time to the second stimulus acts as the "dependent variable". An example of a PRP paradigm might be that there is a task 1 which requires participants to push the keyboard-letter 'n' with the right index finger when a square frame was