According to Pervin (1975), a projective technique ‘is an instrument that is considered especially sensitive to covert or unconscious aspects of behavior, permits or encourages a wide variety of subject responses, is highly multidimensional, and evokes unusually rich or profuse response data with a minimum of subject awareness concerning the purpose of the test’ (p. 33).

In Projective techniques subjects are asked to interpret or fill in visual stimuli, complete sentences, or report what associations particular words bring to mind. Because of the leeway provided by the tests, subjects project their own personalities onto the stimulus, often revealing personal conflicts, motivations, coping styles, and other characteristics.

Major techniques and their classification

The projective techniques are classified by the nature of the response evoked from the subject as follows:

1. Association techniques

The subject is instructed to respond to the stimulus with the first word, image, or percept that occurs to him.

a. Word association 
A series of disconnected words are orally presented, one at a time. Subject is instructed to respond with the first word that occurs to him. Subject’s association and reaction time to each word are recorded. Interpretation involves analysis of the content of the associations, in terms of their relevance to particular motives or conflict areas such as dominance or aggression, or the subject’s responses may be compared with the typical performance of psychiatric and normal groups on the same list of words.

b. Rorschach (Rorschach 1921) and other inkblot techniques
It consists of ten symmetrical inkblots. The cards are presented individually and in a set order. Subject is instructed to report what the figures resemble or suggest to him. Responses to each card are recorded verbatim and reaction times are noted. Then an inquiry is conducted where the subject identifies the characteristics of the stimuli which affected his associations. Various aspects of responses are scored ex: location, relative size of the blot area, use of color and shading, presence of movement etc.

Holtzman Inkblot Technique (Holtzman et al. 1961), introduced desirable psychometric properties to the basic Rorschach approach.

2. Construction techniques

They require the subject to create or construct a more elaborate product, typically a complete art form, such as a story or picture.

a. Thematic Apperception Test (Murray 1943)
It consists of cards containing black-and-white pictures of vague scenes. Subject is required to compose a story to fit each picture, describing what the people are thinking and feeling, what led up to the scene depicted, and what the outcome will be. Scoring is based on the content of behavior and experiences described in the story. The basic assumption is psychological isomorphy between dispositions attributed to the part of the major character in the story and those that exist in the storyteller.

b. The Blacky Pictures test (Blum 1949)
It is intended to investigate 11 specific psychoanalytic variables, including oral eroticism, oedipal intensity, and castration anxiety. The test consists of 12 cartoons concerned with experiences in the life of a dog named Blacky, including his relationships with Mama, Papa, and Tippy, a sibling. The procedure involves story construction in response to the pictures but adds indications of preference and a series of direct questions for each picture. While administration is highly standardized, scoring and interpretation are not.

3. Completion techniques

Subject is presented some type of incomplete product, and asked to complete it in any manner he wishes.
Sentence-completion tests (Ex: Rotter & Wilierman 1947)

The device consists of thirty to one hundred brief sentence stems which the subject is instructed to complete with the first words that come to mind. Sometimes it is emphasized that the completions should reveal subject’s own feelings.The technique is considered most efficient in assessing the content of personality (attitudes, motives, and conflicts) at a more conscious or manifest level than such instruments as the
Rorschach or TAT.

Other examples of completion tests are story-completion and argument-completion tests and the Rosenzweig Picture-Frustration Study (Rosenzweig 1949).

4. Choice or ordering techniques

They require the respondent to choose the item or arrangement (or even hypothetical response) that fits some specified criterion, such as meaningfulness, relevance, or attractiveness from a number of alternatives.

a. The Szondi Test
The test materials consist of 48 photographs of individuals drawn from eight psychiatric diagnostic categories. The subject’s expressions of preference for the different photographs are elicited. While recommendation of repeated administrations and highly objective scoring system make it useful, empirical verification attempts have been negative (Borstelmann & Klopfer 1953).

b. TomkinsHorn Picture Arrangement Test
This device consists of 25 plates. Each contains three line drawings that depict the same figure involved in different but related activities. Subject is asked to indicate the order in which these activities took place and to provide a sentence indicating what is going on in the picture. Rare response patterns are used to estimate certain tendencies such as hypochondriasis or avoidance of people and for distinguishing normal from abnormal subjects. Existence of a highly objective scoring procedure and demonstration of distinct differences in the performances of normal and disturbed subjects make it useful. Cons include delimited data collection.

5. Expressive techniques

They place emphasis upon the manner and style in which the product is created. They are often considered to be therapeutic as well as diagnostic devices, since the subject is presumed to relieve his difficulties in the process of revealing them.

a. Play
These approaches present the subject with an array of toys which he is encouraged to use in some manner. Among the objects frequently selected are dolls representing adults and children of both sexes and various age levels. The examiner is responsible for recording as much of the subject’s behavior as possible, including choice and arrangement of toys, accompanying comments, and expressive behavior. The examiner recognizes important motives and conflicts when he sees them.

b. Drawing and painting
Attention has centered chiefly on procedures using drawings of the human figure, the most publicized of which have been those of Buck (1948) and Machover (1949). When the test is administered individually, the examiner usually notes the subject’s comments, the sequence of parts drawn, and other procedural details. Scoring of human-figure-drawing tests is essentially qualitative, being concerned with such stylistic features as the figure’s stance, size, and position on the page, disproportions, shading, and erasures.

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A projective test is a personality test designed to let a person respond to ambiguous stimuli, presumably revealing hidden emotions and internal conflicts projected by the person into the test. The five types of techniques when classified by nature of response are association techniques, construction techniques, completion techniques, choice or ordering techniques and expressive techniques.

Sources:
http://www.encyclopedia.com/doc/1G2-3045000995.html
http://en.wikipedia.org/wiki/Projective_test
Gale Encyclopedia of Psychology
Encyclopedia of Applied Psychology (Click for eBook)