Current theories of the psychology of ambivalence This question querying the authenticity of people's words and actions and the resulting commentary after this answer, has led me to ask this question.
Ambivalence is a state of having simultaneous, conflicting feelings toward a person or thing.1 Stated another way, ambivalence is the experience of having thoughts and/or emotions of both positive and negative valence toward someone or something. The term also refers to situations where &quot;mixed feelings&quot; of a more general sort are experienced, or where a person experiences uncertainty or indecisiveness concerning something. The expressions &quot;cold feet&quot; and &quot;sitting on the fence&quot; are often used to describe the feeling of ambivalence.

Ambivalence is experienced as psychologically unpleasant when the positive and negative aspects of a subject are both present in a person's mind at the same time. This state can lead to avoidance or procrastination, or to deliberate attempts to resolve the ambivalence. When the situation does not require a decision to be made, people experience less discomfort even when feeling ambivalent.
It is normal to have ambivalence from time to time about how we feel about another individual, whether we can trust the authenticity of a person. As human beings are multidimensional creatures. Trials and triumphs both bring out different aspects that are part of the one person. A person's mood, can change the way that person relates to others. Combined with the modulation of the observer's own internal processes, there can be a varying perception between two people.

If my ideas are correct, and a degree of ambivalence can be quite normal, almost expected within human interactions (or relationships);
How can  reasonable ambivalence be differentiated from  pathological ambivalence?
What are the current theories regarding the psychology of  ambivalence?
Many studies have examined ambivalence, 


  Interest in attitudes and ambivalence has highlighted problems with the adequacy of conceptualizing attitudes as unitary, unidimensional, evaluations...//..
   the hypothesis that ambivalence will attenuate observed attitude-intention relationships (since the evaluations influencing the expression of attitudes are more likely to differ from the evaluations influencing the expression of intentions for people who are more ambivalent. 1
  
  Negative interactions may occur with ambivalent social partners (i.e., partners involved in both positive and negative exchanges) or exclusively problematic social partners (i.e., partners involved in negative exchanges only), but conflicting views exist in the literature regarding which type of social partner is likely to be more detrimental to older adults' physical and emotional health. 2


Pathological ambivalence appears to be rooted in infancy 3 and/or childhood, and is categorised as an attachment disorder, known as Ambivalent Attachment Disorder or Anxious-Ambivalent Attachment Disorder or a type of Reactive Attachment Disorder 4 under the umbrella of Insecure Attachment Disorders.   

It is theorised to be causal, or at least linked to psychopathy 5 and personality disorders, in particular, Borderline Personality Disorder 6. It is theorised to begin in infancy and/or childhood. When a child's needs are met inconsistently. 


  The first type of insecure attachment is called ambivalent attachment. This occurs when caregivers are inconsistent – sometimes answering infants’ needs quickly and responsively, and sometimes letting the infant ‘cry it out’. This may also occur if caregivers respond only to the physical needs – feeding, changing, etc, but ignore the infant’s need for human interaction and connection.
  
  Looking at baby, touching, singing, talking about what we are doing, etc is very important for infants’ emotional development. Without this, babies do not ‘feel felt’, an expression coined by Dan Siegel in his book ‘Parenting From the Inside Out’. It can become very difficult for these babies to develop the qualities of compassion and empathy.
  
  With insecure ambivalent attachment characterized by ‘only sometimes’ type of caregiving, babies learn that the world and their ability to have an impact on it is basically inconsistent – sometimes things happen, sometimes they don’t – sometimes all their needs are met, and sometimes only some of them are. Infants learn that others are not dependable or consistent. They often also do not learn or understand emotions – their own or others. 3


Being deprived of basic care, the child manifests an ideation that there is not enough to provide for everyone in this world, and so will grab to get their needs and/or wants met.


  AMBIVALENT ATTACHMENT DISORDER (AmAD) children see scarcity everywhere, and therefore what is wanted should be taken as it is not going to be given by anyone. Having to hurt someone to get what is wanted is viewed simply as “the cost of doing business”, and the other person is seen as deserving being hurt for having been in the way.


Attachment, Parental Bonding and Borderline Personality Disorder Features in Young Adults


  Hierarchical regression analyses revealed that parental bonding and attachment scores (especially insecure attachment, anxious or ambivalent attachment, and a perception of a relative lack of caring from one's mother) were uniquely associated with borderline features beyond what could be accounted for by gender, childhood adversity experiences, Axis I disorder, and nonborderline Axis II symptoms. Although relatively modest, these relations suggest that bonding and attachment constructs might be considered in comprehensive etiological models of borderline personality disorder.


Symptoms of Ambivalent Reactive Attachment Disorder are:  


  
  Passion to intimate contact and declarations of love at all times from their partners;
  Show inveterate care giving nature;
  Tend to idealize others;
  Feel themself uncomfortable with anger;
  Show too extreme emotions;
  Very jealous;
  Frequent mood swings;
  Imbalanced relationships with others;
  Never have prolonged relationships;
  Too possessive;
  Feel that their partner is unpredictable;
  Tend to be concerned or have dependence on relationship;
  May show suicide attempts;
  Have a tendency of frequent depression;
  Often feel themself unlovable or undesired by others. 
  


 1. 
Br J Health Psychol. 2001 Feb;6(Pt 1):53-68.
Ambivalence about health-related behaviours: an exploration in the domain of food choice.
Sparks P, Conner M, James R, Shepherd R, Povey R.
Source
School of Social Sciences, University of Sussex, Falmer, Brighton, UK. P.Sparks@sussex.ac.uk
Psychol Aging. 2012 Dec;27(4):912-23. doi: 10.1037/a0029246. Epub 2012 Jul 9.
2. 
Ambivalent versus problematic social ties: implications for psychological health, functional health, and interpersonal coping.
Rook KS, Luong G, Sorkin DH, Newsom JT, Krause N.
Source
Department of Psychology and Social Behavior, University of California, Irvine, CA 92697-7085, USA. ksrook@uci.edu
Attachment, Parental Bonding and Borderline Personality Disorder Features in Young Adults
Angela D. Nickell, Carol J. Waudby, Timothy J. Trull, (2002). Attachment, Parental Bonding and Borderline Personality Disorder Features in Young Adults. Journal of Personality Disorders: Vol. 16, No. 2, pp. 148-159.
doi: 10.1521/pedi.16.2.148.22544
Maryland's Source for 
Attachment Disorder Related Information
Reactive attachment disorder
Insecure Attachment