Attachment measures refer to the various procedures used to assess attachment in children and adults.
Researchers have developed various ways of assessing attachment in children. A variety of methods allow children to be classified into four attachment styles: secure, anxious-ambivalent, anxious-avoidant, and disorganized/disoriented, or assess disorders of attachment. These classifications are also referred to as Secure (Group B); Anxious/Resistant (Group C); Avoidant (Group A) and Disorganized (Group D). Each organized style is further broken down into several sub-categories. A child classified with the disorganized style will be given a "next best fit" organized classification as disorganized attachment is thought to represent a break-down of attachment strategy.
Attachment in adults is commonly measured using the Adult Attachment Interview and self-report questionnaires. Self-report questionnaires have identified two dimensions of attachment, one dimension dealing with anxiety about the relationship, and the other dimension dealing with avoidance in the relationship. These dimensions define four styles of adult attachment: secure, preoccupied, dismissive-avoidant, and fearful-avoidant.
Some methods are based on observation of infants and toddlers either in natural or 'arranged' situations. Other methods, suitable for older children, are based on asking children to complete Stem Stories, respond to pictures or to describe their relationships.
The Strange Situation procedure was formulated to observe attachment relationships between a caregiver and children between the age of nine and 18 months. It was developed by Mary Ainsworth, a developmental psychologist Originally it was devised to enable children to be classified into the attachment styles known as secure, anxious-avoidant and anxious-ambivalent. As research accumulated and atypical patterns of attachment became more apparent it was further developed by Main and Solomon in 1986 and 1990 to include the new category of disorganized/disoriented attachment.
In this procedure the child is observed playing for 20 minutes while caregivers and strangers enter and leave the room, recreating the flow of the familiar and unfamiliar presence in most children's lives. The situation varies in stressfulness and the child's responses are observed. The child experiences the following situations:
Two aspects of the child's behaviour are observed:
The Strange Situation is not designed for children older than about 18 months, and there is an ongoing effort to develop assessment methods that are suitable for older toddlers and preschoolers. The methods in development are intended as research measures, not as diagnostic techniques for individual children. As such, these techniques need to be "lean" enough to carry out fairly quickly. They also need to include ways of guarding against "coder drift", the tendency of evaluators to change their criteria as they assess more and more children over long periods of time. Effective training of evaluators is essential, as some items to be assessed are somewhat subjective (e.g., child is "suddenly aggressive toward mother for no reason"). 
A version of the Strange Situation procedure designed for an older age group of between 3 and 4 years by Cassidy, Marvin and the MacArthur Working group.
This method, devised by Waters and Deane in 1985, utilises Q-Sort methodology. It is based on a set period of observation of children aged 1 – 5 in a number of environments. It consists of nearly 100 items intended to cover the spectrum of attachment related behaviors including secure base and exploratory behaviors, affective response and social cognition. It can rate a child along a continuum from secure to insecure but does not classify the type of insecurity. The current version is Attachment Q-set Version 3.0, 1987.
This system, devised in 1988, analyses the reunion of child and parent after a 1 hour separation. It is aimed at 6 year olds and classifies their attachment status. 
The PAA was devised by P.Crittenden for the purpose of assessing patterns of attachment in 18-month to 5 year old children. Like the SSP it involves an observation which is then coded. The classifications include all the SSP categories plus patterns that develop during the second year of life. The three basic strategies for negotiating interpersonal relationships are modified to fit preschoolers and the patterns are renamed secure/balanced, or Type B, defended, or Type A and coercive or Type C. It is also intended to be able to distinguish the unendangered from the endangered compulsive and obsessive subpatterns that may have implications for emotional and behavioral development.
More recent research uses the Disturbances of Attachment Interview or "DAI" developed by Smyke and Zeanah, (1999). This is a semi-structured interview designed to be administered by clinicians to caregivers. It covers 12 items, namely having a discriminated, preferred adult, seeking comfort when distressed, responding to comfort when offered, social and emotional reciprocity, emotional regulation, checking back after venturing away from the care giver, reticence with unfamiliar adults, willingness to go off with relative strangers, self endangering behavior, excessive clinging, vigilance/hypercompliance and role reversal. This method is designed to pick up not only reactive attachment disorder but also Zeannah et al.'s (1993) suggested new alternative categories of disorders of attachment. 
With older toddlers, children, and teens, three different techniques to determine their state of mind with respect to attachment are used. The first is the Story Stem in which children are asked to complete and describe stories having been given the 'stem' or beginning. The second method asks children to respond to pictures. The third involves asking children actual questions about their attachment relationships.
This method uses dolls and narrative to enact a story. The dolls represent family members. The interviewer enacts the beginning of the story and then hands the dolls over for the child to complete it with varying degrees of prompting and encouragement. These techniques are designed to access the childs internal working models of their attachment relationships. Methods include the MacArthur Story Stem Battery (MSSB) developed in 1990 for children between the age of 3 to 8 years; the Story Stem Assessment Profile (SSAP) developed in 1990 for children aged 4 – 8; the Manchester Child Attachment Story Task (MCAST) developed in 2000 for children aged 4.5 - 8.5 and the Attachment Story Completion Test. Results are usually videod and coded.
Like the stem stories, these techniques are designed to access the childs internal working models of attachment relationships. The child is shown attachment related pictures and asked to respond. Methods include the Separation Anxiety Test (SAT) developed in 1972 for children aged between 11 and 17. Revised versions have been produced for 4 - 7 year olds.
This is a semi-structured interview designed by Target et al. (2003) for children aged 7 to 11. It is based on the Adult Attachment Interview, adapted for children by focussing on representations of relationships with parents and attachment related events. Scores are based on both verbal and non-verbal communications.
This again is a version of the Adult Attachment Interview (AAI) rendered age appropriate for adolescents. The classifications of dismissing, secure, preoccupied and unresolved are the same as under the AAI described below.
Existing measures have not necessarily been developed to a useful level. "Behavioral observation is a natural starting point for assessing attachment disorders because behavioral descriptions... have been central to the development of the concept... despite the fact that observations have figured prominently... no established observational protocol has been established" 
Also, questionable measures of attachment in school-age children have been presented. For example, a protocol for establishing attachment status was described by Sheperis and his colleagues . Unfortunately, this protocol was validated against another technique, the Randolph Attachment Disorder Questionnaire, that was itself poorly validated and that is based on a nonconventional view of attachment.
"It is by no means free of limitations (see Lamb, Thompson, Gardener, Charnov & Estes, 1984). To begin with, it is very dependent on briefseparations and reunions having the same meaning for all children. This maybe a major constraint when applying the procedure in cultures, such as that in Japan (see Miyake et al.,, 1985), where infants are rarely separated from their mothers in ordinary circumstances. Also, because older children have a cognitive capacity to maintain relationships when the older person is not present, separation may not provide the same stress for them. Modified procedures based on the Strange Situation have been developed for older preschool children (see Belsky et al., 1994; Greenberg et al., 1990)[16 ] but it is much more dubious whether the same approach can be used in middle childhood. Also, despite its manifest strengths, the procedure is based on just 20 minutes of behaviour. It can be scarcely expected to tap all the relevant qualities of a child's attachment relationships. Q-sort procedures based on much longer naturalistic observations in the home, and interviews with the mothers have developed in order to extend the data base (see Vaughn & Waters, 1990). A further constraint is that the coding procedure results in discrete categories rather than continuously distributed dimensions. Not only is this likely to provide boundary problems, but also it is not at all obvious that discrete categories best represent the concepts that are inherent in attachment security. It seems much more likely that infants vary in their degree of security and there is need for a measurement systems that can quantify individual variation".
With respect to the ecological validity of the Strange Situation, a meta-analysis of 2,000 infant-parent dyads, including several from studies with non-Western language and/or cultural bases found the global distribution of attachment categorizations to be A (21%), B (65%), and C (14%)  This global distribution was generally consistent with Ainsworth et al.'s (1978) original attachment classification distributions.
However, controversy has been raised over a few cultural differences in these rates of 'global' attachment classification distributions. In particular, two studies diverged from the global distributions of attachment classifications noted above. One study was conducted in North Germany [19 ] in which more avoidant (A) infants were found than global norms would suggest, and the other in Sapporo, Japan  where more resistant (C) infants were found. Of these two studies, the Japanese findings have sparked the most controversy as to the meaning of individual differences in attachment behavior as originally identified by Ainsworth et al. (1978).
In a recent study conducted in Sapporo, Behrens, et al., 2007.  found attachment distributions consistent with global norms using the six-year Main & Cassidy scoring system for attachment classification.[22 ] In addition to these findings supporting the global distributions of attachment classifications in Sapporo, Behrens et al. also discuss the Japanese concept of amae and its relevance to questions concerning whether the insecure-resistant (C) style of interaction may be engendered in Japanese infants as a result of the cultural practice of amae.
Regarding the issue of whether the breadth of infant attachment functioning can be captured by a categorical classification scheme, it should be noted that continuous measures of attachment security have been developed which have demonstrated adequate psychometric properties. These have been used either individually or in conjunction with discrete attachment classifications in many published reports [see Richters et al., 1998;  van Ijzendoorn et al., 1990). ] The original Richter’s et al. (1998) scale is strongly related to secure versus insecure classifications, correctly predicting about 90% of cases . Readers further interested in the categorical versus continuous nature of attachment classifications (and the debate surrounding this issue) should consult the paper by Fraley and Spieker [25 ] and the rejoinders in the same issue by many prominent attachment researchers including J. Cassidy, A. Sroufe, E. Waters & T. Beauchaine, and M. Cummings.
The two main ways of measuring attachment in adults include the Adult Attachment Interview (AAI) and self-report questionnaires. The AAI and the self-report questionnaires were created with somewhat different aims in mind. Shaver and Fraley note:
"If you are a novice in this research area, what is most important for you to know is that self-report measures of romantic attachment and the AAI were initially developed completely independently and for quite different purposes. One asks about a person's feelings and behaviors in the context of romantic or other close relationships; the other is used to make inferences about the defenses associated with an adult's current state of mind regarding childhood relationships with parents. In principle, these might have been substantially associated, but in fact they seem to be only moderately related--at least as currently assessed. One kind of measure receives its construct validity mostly from studies of romantic relationships, the other from prediction of a person's child's behavior in Ainsworth's Strange Situation. Correlations of the two kinds of measures with other variables are likely to differ, although a few studies have found the AAI to be related to marital relationship quality and a few have found self-report romantic attachment measures to be related to parenting." (Shaver & Fraley, 2004) 
The AAI and the self-report questionnaires offer distinct, but equally valid, perspectives on adult attachment. It's therefore worthwhile to become familiar with both approaches.
Developed by Mary Main and her colleagues, this is a semi-structured interview that takes about one hour to administer. It involves about twenty questions and has extensive research validation to support it. A good description can be found in Chapter 19 of Attachment Theory, Research and Clinical Applications, edited by J. Cassidy and P. R. Shaver, Guilford Press, NY, 1999. The chapter title is "The Adult Attachment Interview: Historical and Current Perspectives," and is written by E. Hesse.
Some of the strongest external validation of the measures involves its demonstrated ability to predict interviewees' children's classifications in the Strange Situation. The measure also has shows to have some overlap with attachment constructs measured by the less time-intensive measures of the peer/romantic attachment tradition (Hazan & Shaver, Bartholomew), as reported by Shaver, P. R., Belsky, J., & Brennan, K. A. (2000).[27 ] However, there are important differences in what is measured by the AAI—rather than being a measure of romantic attachment, it taps primarily into a person's state of mind regarding their attachment in their family of origin (nuclear family).
Hazan and Shaver created the first questionnaire to measure attachment in adults.  Their questionnaire was designed to classify adults into the three attachment styles identified by Ainsworth. The questionnaire consisted of three sets of statements, each set of statements describing an attachment style:
- Secure - I find it relatively easy to get close to others and am comfortable depending on them and having them depend on me. I don't often worry about being abandoned or about someone getting too close to me.
- Avoidant - I am somewhat uncomfortable being close to others; I find it difficult to trust them completely, difficult to allow myself to depend on them. I am nervous when anyone gets too close, and often, love partners want me to be more intimate than I feel comfortable being.
- Anxious/Ambivalent - I find that others are reluctant to get as close as I would like. I often worry that my partner doesn't really love me or won't want to stay with me. I want to merge completely with another person, and this desire sometimes scares people away.
People participating in their study were asked to choose which set of statements best described their feelings. The chosen set of statements indicated their attachment style. Later versions of this questionnaire presented scales so people could rate how well each set of statements described their feelings.
One important advance in the development of attachment questionnaires was the addition of a fourth style of attachment. Bartholomew and Horowitz presented a model that identified four categories or styles of adult attachment.  Their model was based on the idea attachment styles reflected people's thoughts about their partners and thought about themselves. Specifically, attachment styles depended on whether or not people judge their partners to be generally accessible and responsive to requests for support, and whether or not people judge themselves to be the kind of individuals towards which others want to respond and lend help. They proposed four categories based on positive or negative thoughts about partners and on positive or negative thoughts about self.
Bartholomew and Horowitz used this model to create the Relationship Questionnaire (RC). The RC consisted of four sets of statements, each describing a category or style of attachment:
- Secure - It is relatively easy for me to become emotionally close to others. I am comfortable depending on others and having others depend on me. I don't worry about being alone or having others not accept me.
- Dismissive - I am comfortable without close emotional relationships. It is very important to me to feel independent and self-sufficient, and I prefer not to depend on others or have others depend on me.
- Preoccupied - I want to be completely emotionally intimate with others, but I often find that others are reluctant to get as close as I would like. I am uncomfortable being without close relationships, but I sometimes worry that others don't value me as much as I value them.
- Fearful - I am somewhat uncomfortable getting close to others. I want emotionally close relationships, but I find it difficult to trust others completely, or to depend on them. I sometimes worry that I will be hurt if I allow myself to become too close to others.
Tests demonstrated the four attachment styles were distinct in how they related to other kinds of psychological variables. Adults indeed appeared to have four styles of attachment instead of three attachment styles.
David Schmitt, together with a large number of colleagues, validated the attachment questionnaire created by Bartholomew and Horowitz in 62 cultures.  The distinction of thoughts about self and thoughts about partners proved valid in nearly all cultures. However, the way these two kinds of thoughts interacted to form attachment styles varied somewhat across cultures. The four attachment styles had somewhat different meanings across cultures.
A second important advance in attachment questionnaires was the use of independent items to assess attachment. Instead of asking people to choose between three or four sets of statements, people rated how strongly they agreed with dozens of individual statements. The ratings for the individual statements were combined to provide an attachment score. Investigators have created several questionnaires using this strategy to measure adult attachment.
Two popular questionnaires of this type are the Experiences in Close Relationships (ECR) questionnaire and the Experiences in Close Relationships - Revised (ECR-R) questionnaire. The ECR was created by Brennan, Clark, and Shaver in 1998. [31 ] The ECR-R was created by Fraley, Waller, and Brennan in 2000. [32 ] Readers who wish to take the ECR-R and learn their attachment style can find an online version of the questionnaire at http://www.web-research-design.net/cgi-bin/crq/crq.pl.
Analysis of the ECR and ECR-R reveal that the questionnaire items can be grouped into two dimensions of attachment. One group of questionnaire items deal with how anxious a person is about their relationship. These items serve as a scale for anxiety. The remaining items deal with how avoidant a person is in their relationship. These items serve as a scale for avoidance. Many researchers now use scores from the anxiety and avoidance scales to perform statistical analyses and test hypotheses.
Scores on the anxiety and avoidance scales can still be used to classify people into the four adult attachment styles. [31 ] [33 ] [34 ] The four styles of attachment defined in Bartholomew and Horowitz's model were based on thoughts about self and thoughts about partners. The anxiety scale in the ECR and ECR-R reflect thoughts about self. Attachment anxiety relates to beliefs about self-worth and whether or not one will be accepted or rejected by others. The avoidance scale in the ECR and ECR-R relates to thoughts about partners. Attachment avoidance relates to beliefs about taking risks in approaching or avoiding other people. Combinations of anxiety and avoidance can thus be used to define the four attachment styles. The secure style of attachment is characterized by low anxiety and low avoidance; the preoccupied style of attachment is characterized by high anxiety and low avoidance; the dismissive avoidant style of attachment is characterized by low anxiety and high avoidance; and the fearful avoidant style of attachment is characterized by high anxiety and high avoidance.