Friday, April 2, 2010

Feeling good: the perception of what is “pleasant” to the touch

Something strokes your skin and you shiver with pleasure. Or is it displeasure? Whether it is pleasant or unpleasant, touch forms a cornerstone of social behavior in humans. Before we even opened our eyes as babies, we tried to make sense of our surroundings through our skins. We touch to learn, to show affection and feel pleasure.

It is important for us to understand how the touch of various materials influences our emotional responses, as the sense of touch is one of the major ways we, as humans, gather information about the world. Now, scientists have revealed that males and females have different perceptions of what is pleasant to the touch.

Previous investigations about pleasant touch suggested soft and smooth materials as pleasant; those that were stiff, rough, or coarse as unpleasant. However, these investigations did not have any numbers to back them up, nor did they consider the possibility of there being differences between males and females.

A research team led by Greg Essick of UNC Chapel Hill in North Carolina decided to fill in these gaps in the knowledge of tactile stimulation, or what they call “pleasantness-to-touch.” Their study, published online in Neuroscience & Biobehavioral Reviews on February 21, 2010, sought to make a quantitative assessment of people’s perceptions of pleasant touch. In other words, by using controlled experiments and gathering concrete data, the scientists can identify what and where females feel pleasantness differently than males.

In the experiment, a rotary tactile stimulator (pictured below) was used to control how the materials brush across the skin while a participant entered in their “pleasantness rating” on a scale of 100% unpleasant to 100% pleasant. “Pleasantness” of contact was noted as affective touch, or touch that evoked a positive emotional response to tactile stimulation.

There were 21 male and 22 female participants. After repeating the process several times, 16 stimulus trials per participant, the researchers obtained ratings of pleasantness of different textured materials stroked across the skin of multiple body sites at controlled velocities and forces of application.

Their data supports previous results that smooth stimuli are pleasant, and that they continue to be pleasant even with increased force. Conversely, rough stimuli start out neutral and become more unpleasant as the force is increased.

The most unexpected findings were that males found stimulation of the forehead, particularly for terry toweling and denim, unpleasant, whereas female participants found terry toweling and denim to be unpleasant on the hand and thigh. For materials that were more pleasant, gendered-responses were similar when tested on the hand, forearm, and thigh. Interestingly, male participants found stimulation of the calf more pleasant than female participants.

This was the first study to conclude, based on data, that there are differences between male and female responses to unpleasant materials. They believe this phenomenon most likely due to sex-dependent mechanical responses of the skin.

We all know that males and females have areas that are more sensitive than others, but who would have thought there are some pretty mundane differences in addition to the sexual ones that usually come to mind.

It is only a first step, but as we continue to learn about, and assign values to the different emotional responses to touch, we can begin to understand the psychology of why people are attracted by some things and repulsed by others.

1 comment:

  1. I think that this article is great. I didn't notice how I've read all of it. Didn't have to force myself to continue reading and it flows very nice too. Author's tone stays the same and no breaks between the paragraphs. Thanks Hannah.