Subliminal Perception

Perception of a stimulus presented below the threshold for conscious recognition is called subliminal perception. Subliminal means below the normal limen or threshold or limit. An experiment done on the college students can be taken as an illustration for subliminal perception. A set of college students was shown a cartoon character flashed on a screen. The cartoon was paired with photographs of faces expressing joy or disgust. The faces were flashed at a speed that made them undetectable. Since the students have not previously seen the cartoon character, they were forming a first impression. Apparently, the students chose more negative terms to describe the cartoon character that had been paired with a disgusted face.

Many firms have tried subliminal method of advertisements. In one such attempt, the words “Eat popcorn and Drink Coca-cola” were flashed in theatre screens for 1/3000 second every 5 seconds during movies. In the period of 6 weeks the messages ran, the firm claimed an increase of 57.5 percent in popcorn sales and an 18.1 percent increase in Coca-cola sales. However well-controlled experiments have shown that subliminal stimuli are basically weak stimuli. More over, subliminal advertisements have proved largely ineffective. Even so, advertisers still use subliminal messages

SIGNAL DETECTION THEORY in Psychology.

Signal Detection theorystates that the perception of sensory stimuli involves the interaction of physical, biological and psychological factors. The intensity of the signal, the degree to which the signal can be distinguished form background noise and the psychological factors like motivation, expectations and learning together will determine the perception.

The intensity of the stimuli is just one of the factors that determine whether people will perceive sensory stimuli or a difference between two signals. Another is the degree to which the signal can be distinguished from background noise. It is easier to hear a friend in a quiet room than in one where people are clinking silverware and glasses and engaging in competining conversations. The quality of a person's bilogical sensory system is still another factor. Here we are concenred with the sharpness or acuteness of the individual's sensory system. We consider whether sensory capacity is fully developed in diminished because of illness or advanced years.

Signal detection theory also considers psychological factors such as motivation, expectations and learning. One psychological factor in signal detection is focusing or narrowing of attention to signals the person deems important.

Signal detection theory emphasizes the psychological aspects of detecting and responding to signals. The relationship between a physical stimulus and sensory response is more than mechanical or mathematical. Training, learning, motivation and many other psychological states such as fatigue or alertness influences the detection of signals to a large extent.

Psychology as a Science

Psychology, like other sciences, seeks to describe, explain, predict and control the events it studies. Psychology thus seeks to describe, explain, predict, and control behaviour and mental processes.
Psychological theories are based on assumptions about behaviour and mental processes, contain statements about the principles and laws that may govern them and allow us to derive explanations and predictions. Many psychological theories combine statements about behaviour (such as eating or aggression), mental processes (such as attitudes and mental images), and anatomical structures or biological processes. For instance, many of our responses to drugs such as alcohol and marijuana can be measured as overt behaviour, and they are presumed to reflect the biochemical actions of these drugs and our (mental) expectations about their effects.
A satisfactory psychological theory allows us to predict behaviour and mental processes. For instance, a satisfactory theory of hunger will allow us to predict when people will or will not eat. A broadly satisfying comprehensive theory should have a wide range of applicability. A broad theory of hunger might apply to human beings and lower animals, to normal-weight and over-weight people, and to people who have been deprived of food for differing lengths of time. If our observations cannot be adequately explained by, or predicted from a given theory, we should consider revising or replacing that theory.
In psychology, many theories have been found to be incapable of explaining or predicting new observations. As a result, they have been discarded or revised. For example, the theory that hunger results from stomach contractions may be partially correct for normal-weight individuals, but it is inadequate as an explanation for feelings of hunger among the overweight. Contemporary theories focus also on biological variables and situational variables.
The notion of controlling behaviour and mental processes is controversial. Some people erroneously think that psychologists seek ways to make people do their bidding--like puppets on strings. This is not so. Psychologists are committed to a belief in the dignity of human beings, and human dignity demands that people be free to make their own decisions and choose their own behaviour. Psychologists are learning more all the time about the various influences on human behaviour, but they implement this knowledge only upon request and in order to help an individual or organization.