Sexual arousal though they are generally considered secondary in role to the other three. Erotic stimuli which can result in sexual arousal can include conversation, reading, films or images, or a smell or setting, any of which can generate erotic thoughts and memories in a person. Given the right context, these may lead to the person desiring physical contact, including kissing, cuddling, and petting of an erogenous zone. This may in turn make the person desire direct sexual stimulation of the breasts, nipples, buttocks and/or genitals, and further sexual activity. Erotic stimuli may originate from a source unrelated to the object of
Sexual arousal characterized by vasocongestion of the genital tissues, including internal and external areas (e.g., vaginal walls, clitoris, and labia). There are a variety of methods used to assess genital sexual arousal in women. Vaginal photoplethysmography (VPG) can measure changes in vaginal blood volume or phasic changes in vasocongestion associated with each heartbeat. Clitoral photoplethysmography functions in a similar way to VPG, but measures changes in clitoral blood volume, rather than vaginal vasocongestion. Thermography provides a direct measure of genital sexual arousal by measuring changes in temperature associated with increased blood flow to the external genital tissues. Similarly, labial thermistor clips measure