Charles Spearman, not Louis Thurstone, developed the concept of the g factor. The g factor refers to a person's general intelligence that can be reflected in an IQ score. General intelligence is believed to impact a person's performance on cognitive tasks. Louis Thurstone is credited with diverging from the idea of general intelligence and proposing 7 types of primary mental abilities, including verbal comprehension, reasoning, perceptual speed, numerical ability, word fluency, associative memory, and spatial visualization. Daniel Goleman proposed the idea of emotional intelligence, which is the ability to process and understand emotions. Howard Sternberg proposed three components of intelligence: analytical (e.g. problem-solving ability), practical (e.g ability to adapt to change), and creative (e.g. ability to deal with new situations). Howard Gardner identified the following 8 types of intelligence: visual-spatial, verbal-linguistic, bodily-kinesthetic, logical-mathematical, interpersonal, musical, intrapersonal, and naturalistic. Last, Alfred Binet developed the first reliable intelligence test when working with children.

The correct answer is "Hermann Ebbinghaus." He was the first known psychologist to conduct scientific studies on memory. His research began around 1878 and (as briefly explained in the question) involved studying how long an individual could recall nonsense, three-letter words after they were initially studied. Interestingly, Ebbinghaus used himself as his only subject. He repeated the list of meaningless words to himself, waited for a certain amount of time to elapse, and then attempted to recall the full list. He found that he forgot a large amount of the information within an hour and even more within a day; however, after that point, the amount forgotten decreased significantly—that is, if he remembered it for a certain length of time (e.g. about a day), then he would remember it for the relative “long haul.”

Maslow was responsible for the Maslow hierarchy of needs: an ordering of human needs from most pressing to least pressing, often presented as a pyramid. According to Maslow, needs can be grouped into the following categories, from lowest to highest: physiological needs; safety and security; love and belongingness; self-worth and self-esteem; and self-actualization (sometimes subdivided into knowledge and understanding, aesthetic needs, and then self-actualization). The idea is that an individual will focus on filling simpler, more “primitive” needs before moving onto the more abstract human need for growth and development. Physiological needs are things like food, shelter, and water. Safety and security refers to achieving a secure, low fear state in which one feels physically, financially, and emotionally safe and stable. Love and belongingness needs are next, and they are described as the human need for companionship and social relationships. The self-worth and self-esteem tier consists of people’s needs for positive feelings about themselves and their positions in society; it is essentially the desire to be valued as a contributing member of one’s community. Self-actualization is a somewhat abstract concept which is best summarized as “being the absolute best you can be." Maslow thought very few, if any, people ever actually achieved self-actualization. As for the other answer choices, Mary Ainsworth was responsible for attachment theory in small children; Carl Jung, for the concept of archetypes; B. F. Skinner, for operant conditioning.

"Alfred Binet" created the first practical intelligence test by assessing the diverse abilities of Parisian schoolchildren in the 19th century. Even in modern times, his work is still influential. For example, the Stanford-Binet intelligence measure is one of the most popular cognitive tests that is still used today.

"Mary Ainsworth" devised the "Strange Situation" paradigm in the 1970s. It was used to examine the attachment patterns between parent and child. This study identified four primary attachment styles: secure, avoidant, resistant, and disorganized. 

"Albert Bandura" is a psychologist who is best known for devising his social learning theory. This theory posits that learning is a cognitive process that takes place in a social context; furthermore, he theorized that  learning can occur through observation or direct instruction from peers. 

Erik Erikson created the eight stages of psychosocial development. While Kohlberg and Piaget also were interested in development, their research did not involve the psychosocial conflicts and were more focused on morality and theories of "knowing" respectively. Last, Adler founded individual psychology and Horney was a neo-Freudian.

John Watson studied classical conditioning through the Little Albert experiment. In this study Watson presented Albert with a white rat. At the same time he made a loud noise, creating a sense of fear in Albert. Watson then presented Albert with other white, furry objects. He found that Albert generalized his fear response from the white rat to other similar-looking objects. Ivan Pavlov is also known for studying classical conditioning. Edward Thorndike and B.F. Skinner both studied operant conditioning. Albert Bandura studied observational learning. Solomon Asch conducted the famous line studies that showed the power of conformity in groups. Stanley Milgram studied obedience by having research participants believe they were administering electrical shocks to confederates. 

A French philosopher, mathematician and scientist, Rene Descartes set the foundation for much of Western philosophy with his writings on dualism, which purports that the mind and body affect each other, as opposed to the previously agreed upon one-way relationship in which the mind affected the body. The other choices are incorrect. Plato was a Greek philosopher, considered to be an early psychologist, who first scientifically researched the abstract. John Locke was an enlightened Brit who coined ‘tabula rasa’ and first defined the self. Last, Aristotle was a Greek philosopher, considered to be an early psychologist who wrote “On the Soul” and first researched memory

Ivan Pavlov was the first to research classical conditioning using a dog's salivation response to being fed in conjunction with the ringing of a bell. Classical conditioning is sometimes referred to as Pavlovian conditioning. The other choices are incorrect. B.F. Skinner was a behaviorist who discovered operant conditioning. Clark Hull was a rigorous researcher whose claim to fame is creating modern hypnosis. Last, John Watson established the behaviorist school and is most famous for his conditioning experiment with patient Little Albert.