Hockenbury Discovering Psychology 5th txtbk

The Chemical and Body Senses107IN FOCUSDo Pheromones Influence Human Behavior?Many animals communicate by releasing pheromones, chemicalsignals that provide information about social and sexual statusto other members of the same species (Dulac & Torello,2003). Pher omones may mark territories and serve as warningsignals to other members of the same species. Ants usepheromones to mark trails for other ants, as do snakes andsnails. Pheromones are also extremely important in regulatingsexual attraction, mating, and reproductive behavior in many animals(Wyatt, 2009). A lusty male cabbage moth, for example,can detect phero mones released from a sexually receptive femalecabbage moth that is several miles away.Do humans produce pheromones as other animals do? Thebest evidence for the existence of human pheromones comesfrom studies of the female menstrual cycle by University ofChicago biopsychologist Martha McClintock (1992). While still acollege student, McClintock (1971) set out to scientifically investigatethe folk notion that women who live in the same dormeventually develop synchronized men strual periods. McClintockwas able to show that the more time women spent together, themore likely their cycles were to be in sync.Later research showed that smelling an unknown chemicalsubstance in underarm sweat from female donors synchronizedthe recipients’ menstrual cycles with the donors’ cycles (Preti &others, 1986; Stern & McClintock, 1998).Since this finding, McClintock and her co-researchers havemade a number of discoveries in their quest to identify humanpheromones, which they prefer to call human chemosignals.Their search has narrowed to chemicals found in steroid compoundsthat are naturally produced by the human body andfound in sweat, arm pit hair, blood, and semen. In one study,Suma Jacob and McClintock (2000) found that exposure to themale or the female steroid helped women maintain a positivemood after spending two hours filling out a tedious, frustratingquestionnaire. Men’s moods, however, tended to deteriorate afterexposure to either steroid. PET scans of the women showedthat exposure to the steroid increased activity in several key brainareas involved in emotion and attention, including the prefrontalcortex, amygdala, and cerebellum (Jacob & others, 2001).The Scent of AttractionSome perfume manufacturersclaim that theirproducts contain humanpheromones that willmake you “irresistible” tomembers of the oppositesex. But is there any evidencethat pheromonesaffect human sexualattraction?No study as yet has shown that human chemosignals canfunction as an irresistible sexual signal (Brennan & Zufall, 2006).Rather than producing sexual attraction, McClintock (2001) believes,it’s more likely that human chemosignals affect mood andemotional states.Confirming this view, a later study by McClintock’s lab showedthat exposure to a chemical compound in the perspiration ofbreast-feeding mothers significantly increased sexual motivationin other, non-breast-feeding women (Spencer & others, 2004).The study’s authors speculate that the presence of breast- feedingwomen acts as a social signal—an indicator that the social andphysical environment is one in which pregnancy and breastfeedingwill be supported.Thus, rather than triggering specific behaviors, including sexualbehavior, human chemosignals may be social signals, subliminallyaffecting social interactions and relationships in ways thatwe don’t consciously recognize.sensations are first processed in the thalamus before being relayed to the higher braincenters in the cortex. Olfactory neurons are unique in another way, too. They are theonly neurons that directly link the brain and the outside world. The axons of the sensoryneurons that are located in your nose extend directly into your brain!As with the other senses, we experience sensory adaptation to odors whenexposed to them for a period of time. In general, we reach maximum adaptation toan odor in less than a minute. We continue to smell the odor, but we have becomeabout 70 percent less sensitive to it.Olfactory function tends to decline with age. About half of those aged 65 to 80have a significant loss of olfactory function, a number that increases to two-thirdsof people aged 80 and above (Rawson, 2006). At any age, air pollution, smoking,and exposure to some industrial chemicals can decrease the ability to smell. Loss ofolfactory function is also associated with several diseases—including Parkinson’sdisease, schizophrenia, and multiple sclerosis—and may be an early marker ofAlzheimer’s disease (Devanand & others, 2000).pheromonesChemical signals released by an animal thatcommunicate information and affect thebehavior of other animals of the samespecies.