Experimental psychologists utilize experimental techniques to analyze behavioral and mental processes. They typically study such concerns as learning, memory, sensation, and perception. Comparative psychologists are experimental psychologists who focus on behavior in different species. Physiological psychologists investigate the biological substrates of behavior. Clinical psychologists focus on individuals with psychological disorders. They are involved in diagnosis and treatment. Some engage in research and others train future clinicians. This category represents the largest group of psychologists. Counseling psychologists are similar to clinicians but tend to deal with individuals whose problems are less severe. School psychologists help children in a school setting. These children may have academic, emotional, or behavioral problems or may require special education programs. Educational psychologists may also work in a school setting. They typically focus on test and curriculum development. Developmental psychologists are interested in how people change across the life span. They often focus on the extent to which development is shaped by nature, or genetics, and nurture, or environment. Child psychologists are developmental psychologists who emphasize the early periods of development. Personality psychologists study the psychological characteristics that make each of us unique. Social psychologists are interested in the ways in which people are affected by group or social influences. They study topics such as persuasion, attitudes, and conformity. Environmental psychologists focus on how the physical environment influences behavior. They study such matters as noise pollution and overcrowding. Industrial/organizational psychologists study people in the workplace. They focus on issues such as performance appraisal, motivation, and leadership. Health psychologists look at the relationship between psychological factors and physical health. For example, they study how stress affects health. Consumer psychologists are interested in understanding consumer behavior. They explore why people buy certain products or certain brands.