As the name suggests, this field explores how our biology influences our behaviour. While biological psychology is a broad field, many biological psychologists want to understand how the structure and function of the nervous system is related to behaviour (Figure IP.11). As such, they often combine the research strategies of both psychologists and physiologists to accomplish this goal (as discussed in Carlson, 2013).

The research interests of biological psychologists span a number of domains, including but not limited to, sensory and motor systems, sleep, drug use and abuse, ingestive behaviour, reproductive behaviour, neurodevelopment, plasticity of the nervous system, and biological correlates of psychological disorders. Given the broad areas of interest falling under the purview of biological psychology, it will probably come as no surprise that individuals from all sorts of backgrounds are involved in this research, including biologists, medical professionals, physiologists, and chemists. This interdisciplinary approach is often referred to as neuroscience, of which biological psychology is a component (Carlson, 2013).

While biopsychology typically focuses on the immediate causes of behaviour based in the physiology of a human, evolutionary psychology seeks to study the ultimate biological causes of behaviour. To the extent that it's impacted by genetics, a behavioral pattern will demonstrate adaption to its surroundings. These surroundings include the physical environment and, since interactions between organisms can be important to survival and reproduction, the social environment. The evolutionary psychology of humans has enjoyed a resurgence in recent decades. To be subject to evolution by natural selection, a behaviour must have a significant genetic cause. In general, we expect all human cultures to express a behaviour if it is caused genetically, since the genetic differences among human groups are small. The approach taken by most evolutionary psychologists is to predict the outcome of a behaviour in a particular situation based on evolutionary theory and then to make observations, or conduct experiments, to determine whether the results match the theory. It is important to recognize that these types of studies are not strong evidence that a behaviour is adaptive, since they lack information that the behaviour is in some part genetic and not entirely cultural (Endler, 1986). Demonstrating that a trait, especially in humans, is naturally selected is extraordinarily difficult; perhaps for this reason, some evolutionary psychologists are content to assume the behaviors they study have genetic determinants (Confer et al., 2010). One other drawback of evolutionary psychology is that the traits that we possess now evolved under environmental and social conditions far back in human history, and we have a poor understanding of what these conditions were. This makes predictions about what is adaptive for a behaviour difficult. Behavioural traits need not be adaptive under current conditions, only under the conditions of the past when they evolved, about which we can only hypothesize.

Scientists interested in the physiological aspects of sensory systems work within the area of sensation and perception.  As such, sensation and perception research is also quite interdisciplinary. Imagine walking between buildings as you move from one class to another. You are inundated with sights, sounds, touch sensations, and smells. You also experience the temperature of the air around you and maintain your balance as you make your way. These are all factors of interest to someone working in the domain of sensation and perception.

As described in a later chapter, our experience of our world is not as simple as the sum total of all of the sensory information put together. Rather, our experience of sensory information (our perception) is complex and is influenced by where we focus our attention, our previous experiences, and even our cultural backgrounds.

Developmental psychology is the scientific study of development across a lifespan. Developmental psychologists are interested in processes related to physical maturation. However, their focus is not limited to the physical changes associated with aging, as they also focus on changes in cognitive skills, moral reasoning, social behaviour, and other psychological attributes.

Early developmental psychologists focused primarily on changes that occurred through reaching adulthood, providing enormous insight into the differences in physical, cognitive, and social capacities that exist between very young children and adults. For instance, research by Jean Piaget demonstrated that very young children do not demonstrate object permanence (the understanding that physical things continue to exist, even if they are hidden from us). If you were to show an adult a toy, and then hide it behind a curtain, the adult knows that the toy still exists. However, very young infants act as if a hidden object no longer exists. The age at which object permanence is achieved is somewhat controversial (Munakata, McClelland, Johnson, and Siegler, 1997).

While Piaget was focused on cognitive changes during infancy and childhood as we move to adulthood, there is an increasing interest in extending research into the changes that occur much later in life. This may be reflective of changing population demographics of developed nations as a whole. As more and more people live longer lives, the number of people of advanced age will continue to increase. Indeed, it is estimated that there were just over 40 million people aged 65 or older living in the United States in 2010. However, by 2020, this number is expected to increase to about 55 million. By the year 2050, it is estimated that nearly 90 million people in this country will be 65 or older (Department of Health and Human Services, n.d.).

There are many interesting examples of social psychological research, and you will read about many of these in other chapters of this textbook. One of the most controversial psychological studies ever was conducted by Stanley Milgram, an American social psychologist most famous for his research on obedience. After the holocaust, Nazi war criminals were was accused of committing mass atrocities, and put on trial. Many people wondered how German soldiers were capable of torturing prisoners in concentration camps, and they were unsatisfied with the excuses given by soldiers that they were "simply following orders." At the time, most psychologists agreed that few people would be willing to inflict such extraordinary pain and suffering on others, simply because they were obeying orders. Milgram decided to conduct research to determine whether or not this was true. Milgram found that nearly two-thirds of his participants were willing to deliver what they believed to be lethal shocks to another person, simply because they were instructed to do so by an authority figure (in this case, a man dressed in a lab coat). This was in spite of the fact that participants received payment for simply showing up for the research study and could have chosen not to inflict pain or more serious consequences on another person by withdrawing from the study. No one was actually hurt or harmed in any way. Milgram’s experiment was a clever ruse that took advantage of research confederates, a term for those who pretend to be participants in a research study but who are actually working for the researcher and have clear, specific directions on how to behave during the research study (Hock, 2009). Milgram’s and others’ studies that involved deception and potential emotional harm to study participants catalyzed the development of ethical guidelines for conducting psychological research that discourage the use of deception of research subjects, unless it can be argued not to cause harm and, in general, requiring informed consent of participants.