Most mammals are equipped with at least two olfactory systems, the main olfactory system and the accessory olfactory system. The latter is frequently called the vomeronasal system, because it originates in the vomeronasal organ, a mucosal pocket enclosed within a capsule partially formed by the vomer bone. The following brief introduction to the fascinating world of this organ is essentially based on the excellent reviews by Doving and Trotier (1998) and by Halpern and Martinez- Marcos (2003).

There is one vomeronasal organ on each side of the base of the nasal septum. In rodents, each organ consists of an elongated tube communicating with the floor of the nasal cavity through a narrow duct (Figure 3.3). This duct constitutes the only connection with the outside world. In some other mammals, like carnivores or ungulates, there is an additional connection between the vomeronasal organ and the outside, the nasopalatine canal (sometimes called the incisive canal) connecting the vomeronasal organ with the mouth. In cats, for (more…)

I decided to use vocalizations as an example of the ways in which potential sexual incentive stimuli need to be analyzed before any conclusion as to their incentive properties can be drawn. We should be able to learn a few lessons from this. Several of these lessons are applicable to any sexual incentive stimulus, while some are limited to those incentive stimuli that are emitted in response to the presence of a conspecific. First, however, we need to discuss the analysis of sexual incentive stimuli from an epistemological point of view. This discussion will appear in the following paragraph.

Odor, or body shape, are stimuli emitted whether there is any potential partner present or not. They are not, therefore, responses to the presence of a potential mate but context-independent characteristics of the subject. At difference, vocalizations are, according to abundant data mentioned above, emitted in response to the presence of an individual of the opposite sex. They are also emitted in other situations, like aggressive (more…)

No stimulus can affect an organism’s behavior if it is not captured by its sense organs. In the case of the human, this basic fact does not constitute any immediate problem, because most of us are well aware of our own sensory capabilities. Many other animals, though, have sensory capacities that are quite different from our own. Everyone knows, or believes to know, that dogs or rats can perceive odors with a sensitivity far beyond ours. Here we have an example of different sensory threshold, which is a quantitative difference. There are also qualitative differences in sensory capacity, even among mammals. Some species may have receptors sensitive to light that others do not see, or to sounds that others do not hear or to tastes that others do not feel. What is perhaps still more disturbing is the existence of entirely different sense organs or sensory receptors. The electric organ of some fishes could be an example of this. The nocturnal fish Gnathonemus petersii detects objects and recognizes the surrounding world through the use of receptors sensitive to changes in the self- (more…)

Desire is a term popular in the literature on human sexual behavior. Due to some undoubtedly unfounded prejudice against fashionable terms, I strongly dislike it. Its precise meaning is unclear and it is extremely difficult to use it in a comparative perspective. Proposing that a female rat desires to engage in copulatory activity is extremely repulsive. I have elsewhere argued, with convincing arguments, that the word ‘desire’ needs to be replaced with the word ‘motivation’ in any scientific text (Agmo et al., 2004). Motivation is a well established concept in the behavioral sciences and it can easily be integrated into a large body of theoretical constructions, where clear definitions are possible. The replacement of desire by motivation allows me, for example, to apply an incentive motivational analysis to the problems of approach to a mate and to the visceral reactions produced by incentive stimuli. Erection or vaginal lubrication can, for example, be analyzed and understood as visceral responses to sexual incentive stimuli. (more…)

Throughout history there have been many descriptions of human copulatory behavior. Most of them belong to the fine arts, some to pornography and a few to the medical sciences. Descriptions satisfying some minimum requirements of objectivity and accuracy are more rare. Without discrediting the early pioneers in sex research, I will start my analysis of copulatory behavior with the extraordinary data collected by Alfred Kinsey and colleagues and published in two landmark books (Kinsey et al., 1948, 1953). Those interested in research on human sexuality prior to the Kinsey studies can find an excellent summary in a charming book (Bullough, 1994). However, there is one extremely interesting text preceding the Kinsey era that I cannot avoid mentioning. In 1926, the Dutch gynecologist, Theodoor Henrik van de Velde, published an account of human sexual behavior (van de Velde, 1965; I have had access only to a reprint of the 1926 edition. All following citations refer to the 1965 reprint), including plenty of advice as to how to increase the pleasure derived from (more…)