Psychology

The most developed theory to explain sex differences in humans, evolutionary psychology claims that males and females faced different demands from their environments in primeval times, their respective reproductive statuses being the key elements of their lives.  Thus, males and females developed differing strategies so as to ensure their success in reproduction and survival.  In evolutionary psychological terms, the differences between men and women are based on differing parental investment (Denisiuk, 2004). 
   
The investment of women in reproduction outweighs the investment of men, hence females develop traits to help them improve their chances to reproduce offsprings that would survive (Denisiuk).  These traits must including a loving attitude, which helps the female in her effort to raise physically and mentally healthy children with a supportive mate.  Hence, women are believed to be more romantic, giving and caring than males.  The male sex, on the contrary, happens to be less concerned with reproduction (Denisiuk).  Males are also less concerned about kind and loving gestures such as serving food to their loved ones, unlike women, who must breastfeed as well.  However, men are expected to act as breadwinners for their mates and children, which requires them to express loyalty and compassion in their relationships.
   
Wang (2007) notes that the human mind is a collection of specialized mechanisms or computational algorithms to solve particular problems recurrent in hominid evolution (406).  These algorithms and mechanisms are applied by Homo sapiens or the wise man, gifted with the faculty of reason (Wang, 407).  Thus, females as rational beings are not only more emotionally expressive than males but also able to inhibit their emotional expression better than males.  This helps them to control their sexual desires before males who are not their sexual partners or spouses.  It also helps them to inhibit their aggression before their infants, thereby giving them an evolutionary advantage (Leigh, 2003). 
   
As a matter of fact, both men and women are rational when it comes to the question of survival through reproduction.  They prefer mates with symmetrical facial features, for example, unblemished and clear skins, as such features are indicative of good health.  Healthy people have good genes.  But, women also prefer males with masculine features, for example, facial hair and muscular bodies.  Such features are indicative of adequate testosterone required for fertility.  Moreover, women prefer older men who are intelligent and have high social standing.  They show preference for wealthy men, too, for the reason that they would like their mates to have sufficient power and resources to take care of their offspring.  After all, women search for mates to spend their entire lives with.  Males, on the other hand, are chiefly interested in impregnating mates to have offsprings.  For this reason, they may or may not become emotionally attached to their mates.  Young females with full breasts and hips in addition to small waists are preferred as these features are indicative of adequate estrogen for successful reproduction (Denisiuk).
   
Also according to evolutionary psychologists, males and females have different reactions to sexual infidelity (Denisiuk).  If a woman strays, her mate would experience sexual jealousy for the reason of uncertainty in paternity of their children (Denisiuk).  Women experience sexual jealousy if their mates are interested in other females for the reason that their mates commitments to their children would be reduced if this happens (Denisiuk).  Another difference between males and females is, of course, the fact that fertility of females declines with age but remains unchanged for males (Walsh, 2009).  Hence, Turner  McAndrew (2006) explain that young women tend to be choosier when it comes to mate selection (198).  Older females, on the other hand, may opt to invest in children who may or may not survive (Turner  McAndrew, 198).  As evolutionary psychologists assume that decisions about parental investment are largely unconscious, older women that choose to invest in children who may or may not survive may feel guided by the emotional state of love (Turner  McAndrew, 198).  Even men may feel that they are guided by such emotional states as they make parental investment decisions (Turner  McAndrew, 198).  In other words, the unconscious need to reproduce may or may not enter the conscious mind through the process of parental investment decision-making.
   
Lastly, Wang notes that parental investment decision-making is based on the concept of utility maximization studied by economists (408).  In this framework, the expected utility of a choice option is calculated as the sum of expected values of the options outcomes weighted by corresponding probabilities of the outcomes (Wang, 408).  As parental investment decisions depend primarily on women who must choose between several men who court them, it is essential for females to estimate discrepancy between their expectations and actual investments made by their partners in the future (Wang, 408).  A male produces enough sperm to inseminate thousands of women through his lifetime (Kenyon, 2006).  A female, on the contrary, cannot produce as many children (Kenyon).  Hence, women desire great investment from their mates.  In fact, female expectations in this regard may exceed average investment made by males.  It is for this reason that a woman should estimate discrepancy between her expectations and actual investment made by her mate in the future as she makes her parental investment decision in the present based on the concept of utility maximization (Wang, 408). 
   
Thus, parental investment decisions are rational, regardless of what males and females are consciously feeling or thinking as they go through the decision-making process.  Given that the two sexes have different types of investments to make in their children, men and women tend to think and act differently toward love and relationships.  Still, the two sexes share the need to survive through their children.  This need may be expressed through love in relationships.