Whenever you survey people about how many sexual partners they have had in their lifetime, you undoubtedly find a lot of variability. Some people report having one or two partners ever, while others report hundreds or perhaps thousands. How do we account for this incredible range in sexual history? A recent study published in Social Cognitive and Affective Neuroscience suggests that it may have something to do with how our brains are “wired” to respond to sexual stimuli.

In this study, researchers recruited 62 men and women from college psychology courses. Participants ranged in age from 18-40 and most were single and heterosexual. All participants began by completing a survey that inquired about how many people they have had sexual intercourse with in the past year. “Sexual intercourse” was defined as “having a penis in the vagina or butt” for purposes of this study.

Afterward, participants were hooked up to an electroencephalographic (EEG) device--basically, participants wore a cap covered with electrodes that was designed to record brain activity patterns. While wearing this device, participants were shown a series of 225 images. Some of the images were sexual in nature and ranged from mildly erotic (e.g., kissing) to sexually explicit (e.g., penetrative intercourse). Participants were also shown a series of other images that were non-sexual and varied in terms of whether they were pleasant (e.g., people skydiving), unpleasant (e.g., mutilated bodies), or neutral (e.g., portraits). The pleasant and unpleasant non-sexual images varied in intensity as well.

In analyzing participants’ response to the images, researchers focused on one specific type of brain activity pattern, known as late positive potential (LPP). LPP signals the extent to which a stimulus evokes a strong reaction and is motivating.

The researchers found that the strength of participants' LPP responses to erotic and sexual images depended upon how many sex partners they had in the last year. For participants with fewer sexual partners (0-1), they showed a lower LPP to mild sexual stimuli and a higher LPP to explicit sexual stimuli. By contrast, for participants with more sexual partners (2+), they showed about equally high LPPs for both mild and explicit sexual stimuli. In other words, people with fewer sexual partners had a brain response that was proportional to the intensity of the stimulus—the more sexually intense the image, the more intense the brain response. However, for people with more sexual partners, the brain’s response to sexual images was pretty much the same (i.e., equally high) regardless of how intense it was.

What these results tell us is that people’s brains seem to respond to sexual imagery in very different ways. For some people, the brain appears to be highly sensitive to all sexual cues, whether they are mild or intense. However, for others, the threshold for sexual arousal is set much higher, meaning that it takes a strong cue to elicit a strong response. Because these differences in brain sensitivity were related to previous number of sex partners, these findings raise the provocative possibility that the way our brains are “wired” to respond to sexual cues could potentially be a key factor in explaining why some people pursue more sexual partners than others.

Want to learn more about Sex and Psychology ? Click here for previous articles or follow the blog on Facebook (facebook.com/psychologyofsex), Twitter (@JustinLehmiller), or Reddit (reddit.com/r/psychologyofsex) to receive updates.

To learn more about this research, see: Prause, N., Steele, V. R., Staley, C., & Sabatinelli, D. (in press). Late positive potential to explicit sexual images associated with the number of sexual intercourse partners. Social Cognitive and Affective Neuroscience.

Image Source: iStockphoto

You Might Also Like: