Evolutionary explanations

Evolutionary explanations - focus on the adaptive nature of behaviour.

Human reproductive behaviour:

Males and females differ in their reproductive capabilities.

1. Males produce approx. 100 million sperm, meaning they have the potential to reproduce many times.

2. Females are born with a limited number of eggs, one of which is released per month for around 35-40 years, meaning they have fewer opportunities to reproduce.

Males may feel more competition with other males to find suitable fertile females, while females may be more selective over male partners who possess the best characteristics to pass on to her limited potential offspring.

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Evolutionary explanations

Sexual selection - a key part of Darwin's theory explaining how evolution is driven by competition for males, and the development of characteristics that ensure reproductive success.

Intrasexual selection:

Individuals of one sex (usually males) must outcompete other members of their sex in order to gain access to members of the other sex. Successful individuals are able to mate and so are able to pass on their genes.

Intersexual selection:

Members of one sex evolve preferences for desirable qualities in potential mates. Members of the opposite sex who possess these characteristics will then gain a mating disadvantage over those who do not.

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Evolutionary explanations

Male strategies:

  • Mate-guarding - males may be protective of their mate to prevent other males having the opportunity of getting her pregnant and therefore leaving them using their resources to raise another male's offspring.
  • Sneak copulation - males may have sex with other females in the absence of their partner to increase the chance of passing on genetic material to more offspring.
  • Size and appearance - males evolved to be larger and some species developed physical attributes to increase the appearance of strength to females.

Female strategies:

  • **** sons hypothesis - females are thought to seek out attractive males so that any sons they produce will be equally attractive and will continue to pass on the genes to another generation.
  • Courtship - females use courtship to select the most suitable male to reproduce with. By making a male spend time and resources in the build up to a relationship, the female can check his suitability for reproduction.
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Buss (1989)

Procedure: 10,000 people from 37 different cultures. Rate each of 18 characteristics on how important they would be in choosing a mate. 4-point scale used.


  • Resources - women more than men desired mates who were 'good financial prospects'. This translated into a desire for men with resources, or qualities such as ambition and industriousness
  • Physical attractiveness - men placed more importance on physical attractiveness. This provides cues to a woman's health and hence her fertility and reproductive value.
  • Youth - men universally wanted mates who were younger than them - an indication that men valued increased fertility in potential mates.
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Evaluation of evolutionary explanations

+ Engaging in risky behaviours - evidence suggests that males may be more likely to engage in risky behaviours, which could be a strategy to indicate to females that they are physically strong and possess genetic strength.

- Ignores non-sexual relationships - the evolutionary explanation ignores relationships that are not sexual and not aimed at reproducing, such as homosexual relationships. If mate choice is based on biological preferences surrounding reproductive success, any relationship not aiming to reproduce is difficult to explain and therefore ignored by this explanation.

- Freud - believed that your parents influence your choice of partner. Apparently, we end up marrying someone who reminds us of the opposite sex parent.

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Physical attractiveness

Physical attractiveness is an element of attraction in relationships and is often the first thing that draws couples together.

What is seen to be physically attractive to one person is likely to be different to someone else, as physical attractiveness is a subjective factor.

Matching hypohesis - claims that when people look for a partner for a romantic relationship, they tend to look for someone whose social desirability approximtely equals their own.

People identify who matches and select candidates.

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Walster (1966)

Aim - to see whether matched attractiveness levels were a precursor to relationship formation.

Procedure - university students were rated for attractiveness by independent judges before being randomly paired with a partner of the opposite sex at a dance. Partners were asked to rate how much they liked their partner and whether they would like to see them again.

Results - partners were most likely to 'like' the partner if they had a high level of physical attractiveness, regardless of their own level of attractiveness. Those who met up again after the dance were likely to be of a similar rating of attractiveness.

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Evaluation of physical attractiveness

+ Research - Walster & Walster (1969) told students that they had been matched by a computer program with a partner, even though matching was done randomly. They asked participants to rate their 'match' when they met, and found that those who were closer in matched physical attractiveness rated each other more favourably than those who were mismatched.

- Culture differences - in cultures where arranged marriage is popular, family members may spend time matching partners on factors like success and social standing while physical attractiveness might be less important. This shows that physical attractiveness may not have universal appeal in attraction.

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Self-disclosure - is when a person reveals intimate personal information about themselves to another person.

At the beginning of a relationship, this may be an important signal that trust is developing between partners. It indicates attraction and is starting point to intimacy in romantic relationship.

Self-disclosure may be important for two reasons:

1. We share more information as we get to know people and trust them more.

2. We feel closer to people and more attracted to them because we disclose information to them.

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Factors affecting the influence of self-disclosure:

  • Gender - females may tend to disclose more and also place more importance on disclosures from a potential partner.
  • Content - what is disclosed could influence attraction from another person.
  • Appropriateness - some kinds of disclosure may be seen as more or less appropriate.
  • Attributions - why a person discloses is important. We are more attracted to someone if they seem to especially want to disclose intimate information to us.
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Sprecher (2013)

Interested in whether reciprocal self-disclosure was more influential in determining attraction than one-sided self-disclosure and listening.

Procedure - 156 US undergraduate students paired into two-person dyads. 2/3 were female-female and 1/3 was male-female. Engaged in a self-disclosure task over Skype. Reciprocal condition: immediately took turns asking questions and disclosing. Non-reciprocal condition: one person asked questions and the other person disclosed and then they switched roles. Researchers assessed liking, closeness, perceived similarity, and enjoyment of the interaction.

Findings - individuals in the reciprocal condition dyads reported more liking, closeness, perceived similarity, and enjoyment of the interaction than did those in the non-reciprocal dyads after the first interaction. It showed that turn-taking self-disclosure reciprocity is more likely to lead to positive interpersonal outcomes than is extended reciprocity.

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Evaluation of self-disclosure

+ Supporting evidence - much research evidence supports the claim that self-disclosure is an important feature of attraction in romantic relationships. This suggests it is a valid explanation of a feature of attraction.

- Research - some of the research into self-diclosure does not differentiate between the type of relationship being studied. For example, self-disclosure may play a different role in attraction in a potentially long-term relatonship than it would be in a fling.

- Personality - the personality of the people involved in the relationship is not necessarily taken into account. Some people may disclose more than others, while some will place more emphasis on receiving self-disclosure from others.

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Attraction: filter theory

Filter theory - we choose romantic partners by using a series of filters that narrow down the 'field of availables' from which we might eventually make our choice.

Social demography - refers to variables such as age, social background and location, which determine the likelihood of individuals meeting in the first place.

For example, those who live closest to us, work with us, socialise in the same places, etc.

Similarity in attitudes - if people share similar attitudes, values and beliefs, communication is easier and so a relationship is likely to progress.

For example, when meeting and getting to know new people, those who have similar attitudes to us will be seen as more attractive and therefore more suitable to develop a relationship with.

Complementarity of needs - refers to how well two people fit together as a couple and meet each  other's needs.

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Kerckhoff & Davis (1962)

Procedure: longitudinal study of 94 dating couples at Duke University in the US; completed two questionnaires - degree to which they shared attitudes and values and degree of need complementarity; 7 months after, completed another questionnaire - how close they felt to their partner to how they felt at the beginning of the study; indicate 'progress' toward permanence'.

Findings: intitially, only similarity appeared to be related to partner closeness. When the researchers divided the couples into short-term and long-term, a difference emerged:

  • Couples that had been seeing each other for less than 18 months, similarity of attitudes and values was the most significant predictor of how close they felt to their partner.
  • Couples that had been seeing each for more than 18 months, only complementarity of needs was predictive of how close each individual felt to their partner.
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Evaluation of the filter theory

- Gender biased - criticised for being gender biased as it does not account for the fact that filters applied by males and females may be different.

- Culturally biased - criticised for being culturally biased as it assumes that all cultures would use the same limiting factors to filter those to whom people are attracted. However, this makes the assumption that all relationships are based on personal choice and are voluntary.

- Change over time - the filters affecting relationship formation may change over time as attitudes change in society. For example, social demographic factors, such as ethnicity, may change in importance. In the 1960s, interracial relationships may not have been common, but evidence from Taylor (2010) suggests that 15% of marriages in 2008 were interracial.

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Social exchange theory

Social exchange theory - the likelihood of a person staying in a relationship is determined by an assessment of what they get out of the relationship compared to what they put in, and how the relationship measures up against what they expect and what they might achieve in a different relationship.

Social exchanges:

  • Rewards - relationships bring certain rewards such as sex, companionship and shared living space.
  • Costs - relationships alsobring costs such as time away from friends and family, sharing finances and arguments.

If both partners see they gain more than they put in, and are in profit, then the relationship will continue. Feeling they are at a loss may mean satisfaction is low and the relationship may end.

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Social exchange theory

Comparison levels: both partners will assess their level of profit and loss regularly to determine their level of satisfaction.There are two comparison levels:

1. The comparison level (CL) assess the number of rewards received and the amount of costs they give to the relationship.

2. The comparison level for alternative relationships (CLalt) assesses the profit offered by the current relationship against any potential profit from an alternative relationship.

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Social exchange theory

Four-stage model (Thibaut and Kelley, 1959):

1. Sampling - many relationships will be started while the person 'tries out' the potential rewards and costs associated with being a couple.

2. Bargaining - once a potential partner is identifie, all of the possible sources of profit and loss are assessed to decide whether to pursue a deeper relationship.

3. Commitment - the relationship continues when the costs are outweighed by the rewards, meaning that attraction will increase.

4. Institutionalisation - the couple settle into the relationship, setting an expectation for what rewards and costs will be tolerated for the continuation of the relationship.

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Kurdek & Schmitt (1986)

Aim: to investigate the importance of social exchange factors in determining relationship quality.

Procedure: 185 couples; 44 heterosexual married couples, 35 co-habiting heterosexual couples, 50 same-sex male couples, and 56 same-sex female couples; each lived together and no children between them; questionnaire without discussing answers with each other. 

Findings: for each type of couple, greater relationship satisfaction was associated with:

  • The perception of many benefits of the current relationship (CL).
  • Seeing alternatives to the current relationship as less attractive (CLA).
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Evaluation of the social exchange theory

- Keeping score - criticise it as it suggests that humans keep score in their relationships, making them appear selfish. While some individuals and/or couples may be the kind to 'keep score', many others will maintain relationships for other reasons, such as mutual respect and trust. This suggests that the theory does not apply to all relationships universally.

- Economic approach - an alternative explanation was put forward to modify the economic approach to relationships by suggesting that rather than profit, couples seek to maintain relationships based on fairness. Equity theory assumes that both partners require the feeling that they are gaining equally rather than each seeking to maximise their own profit margin.

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Equity theory

Equity theory - claims that people are most comfortable when what they get out of a relationship is roughly equal to what they put in.

Inequity in relationshipsWalster (1978) said that each partner in a relationship will 'put in' to a relationship, and will also 'take' from the other partner. So long as each partner remains satisfied that they are both giving and receiving in a fair ratio, they will continue with the relationship. However, if either partner feels that they are giving more than they receive (under-benefitted) or receiving more than they put in themselves (over-benefitted), the level of satisfaction will decrease. This puts the continuation of the relationship under threat.

Motivation to maintain the relationship: When one or both partners feel an imbalance between what they give and receive in the relationship, it creates discomfort. This acts as a motivation to return the relationship to a state of equity or fairness. If one or both partners are not motivated to balance out the ratio of 'giving' and 'receiving', the imbalance may finally end the relationship. 

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Equity theory

A timetable of equity and inequity in marriages: Schafer & Keith (1980) surveyed hundreds of married couples of all ages, noting those whoe felt their marriages were inequitable because of an unfair division of domestic responsibilities. During the child-rearing years, wives often reported feeling under-benefitted and husbands over-benefitted. As a result, marital satisfaction tended to dip. In contrast, during the honeymoon and empty-nest stages, both husbands and wives were more likely to perceive equity and to feel satisfaction with their marriages.

Four principles of equity:

1. Profit -  each partner seeks to gain more than they put in.

2. Distribution - partners will negotiate to ensure the relationship remains equitable and fair.

3. Distress - when unfairness is perceived, dissatisfaction begins. Distress will increase in line with the amount of inequity.

4. Restoring balance - when inequity is detected, partners will be motivated to act torestore the balance.

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Evaluation of equity theory

- Inherently selfish - many people have criticised the equity theory for claiming people are inherently selfish because they are judging relationship satisfaction on the basis of what they are gaining.

- Emotional efforts - some have criticised the equity theory on the basis that much of what people put into a relationship is emotional, and emotion is difficult to measure. The claim that we balance input with gains is therefore problematic.

- Gender differences - DeMaris pointed out that men and women are not equally affected by inequity in romantic relationships. Women tend to perceive themselves as more under-benefitted and less over-benefitted in relationships, compared to men. 

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The investment model of relationships

1. Satisfaction - the positive vs negative effects felt from being in the relationship. Each partner will assess how much the relationship fulfils their needs, whether they are emotional, sexual or other personal needs. If the positive effects outweigh the negative, then the level of satisfaction will be high. Correlational relationship found between satisfaction level and commitment to the relationship.

2. Quality of alternatives - people are always considering other potential alternatives in comparison to their current relationship. When faced with any other possible mate, Rusbult felt that people make a very quick calculation regarding whether their needs can be met with a higher level of satisfaction with the 'new' partner. If the answer is 'yes', then the level of commitment to the current relationship will decrease. If the answer is 'no', then the level of commitment to maintain the current relationship remains high.

3. Investments made - every relationship involves investment of resources made by both partners into the joint partnership. Direct investments include the time and effort put into the relationship, while indirect investments include children, shared friends and possessions the couple may have bought together. The commitment in the current relationship will be highest when the perceived losses associated with ending the relationship outweigh any dissatisfaction felt.

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Le & Agnew (2003)

Procedure: meta-analysis of 52 studies from 1970s and 1990s; different components of the investment model and the relation between them; sample of over 11,000 (54% male & 46% female) from 5 countries.


  • All studies: satisfaction level, quality of alternatives and investment size were highly correlated with relationship commitment. 
  • Correlation between satisfaction level and commitment was found to be significantly stronger than either quality of alternatives and investment size and commitment.
  • Individuals showing higher levels of commitment were more likely to stay in a relationship.
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Evaluation of Rusbult's investment model

+ Evidence - a lot of research evidene gathered to support the theory comes from real romantic relationships, meaning that the evidence has a good degree of external validity as it relates to commitment levels in existing relationships.

- Self-report methods - much of the evidence gathered to support the investment theory relies heavily on self-report methods such as questionnaires. This could challenge the reliability of the data gathered as there are many reasons why people may not answer questions about their relationship honestly.

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Relationship breakdown

Duck's phase model of relationship breakdown - a model of relationship breakdown that describes the different phases that people go through during the dissolution of a romantic relationship.

Intra-psychic phase: 

  • Threshold - 'I cannot do this any more'.
  • One partner feels dissatisfied with the relationship and begins to consider how and when to end the relationship.
  • The dissatisfied partner considers if and when to share their feelings with the other person.

Dyadic phase:

  • Threshold - 'I would be justified in walking away'.
  • The dissatisfied partner shares their feelings and the couple discuss the relationship's status.
  • Resolutions can be discussed and attmepts may be made to restore satisfaction in the relationship.
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Relationship breakdown

Social phase:

  • Threshold - 'I mean it'.
  • If a reoslution is not possible, the couple make their split public and discuss dissatisfaction with people outside of the relationship.
  • Blame-pacing and gossip-spreading may be common in this phase.

Grave-dressing phase:

  • Threshold - 'It is inevitable'.
  • This marks the end of the relationship and this phase is about 'moving on'.
  • Each partner will begin rebuilding their life out of the relationship as well as telling their version of events from the end of the relationship.
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Summary of relationship breakdown model

Intra-psychic phase: social withdrawal; 'rumination' resentment. Brooding on partner's 'faults' and relational 'costs'. Re-evaluation of alternatives to relationship.

Dyadic phase: uncertainty, anxiety, hostility, complaints. Discussion of discontents. Talk about 'our relationship'; equity, roles. Reassurement of goals, possibilities, commitments.

Social phase: going public; support seeking from third parties. Denigration of partner, alliance building. Social commitment, outside forces create cohesion.

Grave-dressing phase: tidying up memories; making relational histories. Stories prepared for different audiences. Saving face.

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Evaluation of relationship breakdown model

+ Face validity - this theory had good face validity as the phases described by Duck are often reported during the end stages of a relationship.

- Individual differences - a relationship can break down for numerous reasons so not the same for everyone. 

- Ethics - ethical concerns of vulnerability,  privacy and confidentiality. It's a sensitive area so it raises how vulnerable someone can be as it won't be their private life anymore.

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Virtual relationships

Virtual relationships -  are relationships that are conducted through the internet rather than face-to-face interactions.

In traditional relationships, communication is carried out in face-to-face interactions. This allows for the presence of verbal and non-verbal forms of communication. Meanings are made clear through body language, gestures, tone of voice, etc. However, in online relationships, communication is reduced to the written word so some meaning(s) may be lost.

One other key difference between traditional and online rereationships is the amount of self-disclosure people engage in.

Jourard proposed the concept of 'broadcasting self-dislosure' to explain the difference between disclosure to a romantic partner and the sharing of personal information in a public situation.

Self-disclosure - is when a person reveals intimate personal information about themselves to another person.

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Self-disclosure in virtual relationships

The role of self-disclosure in virtual relationships:

  • Explanations have focused on the psychological effects of anonymity.
  • Face-to-face: have to have confidence that the information remains confidential.
  • Virtual: reduced risk of them not disclosing it further.
  • Rubin (1975): we are more likely to disclose personal information to people we don't know and probably will never see again. Also, because a stranger does not have access to an individual's social circle, the confidentiality problem is less of an issue.

'Strangers on a train':

1970s: Rubin carried out a series of studies where confederates disclosed personal information about themselves to a complete stranger on trains. He discovered that when confederates disclosed intimate details of their lives to the stranger in the next seat. This was often met with a reciprocal self-disclosure from the stranger.

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Evaluation of virtual relationships

+ Research - virtual communication allows people with poorer social skills to communicate more effectively. This could help vulnerable people access help and support online if they find face-to-face discussions challenging.

- The 'ideal self' - although people may report high levels of intimacy in their online relationships, the self-disclosure shared online may represent a person's 'ideal self' rather than their real 'self'. Virtual relationships allow elements to be hidden.

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Gate - any obstacle to the formation of a relationship.

Face-to-face interaction is said to be gated because it involves many features that can interfere with the early development of a relationship. Examples: physical unattractiveness, a stammer, social anxiety.

The huge advantage of virtual relationships is the absence of gating. This means that the relationship can develop to a point where self disclosure becomes more frequent and deeper. This absence of gating allows an online relationship to 'get off the ground' in a way that is less likely to happen in a face-to-face situation. Absence of gating works by re-focussing attention on self-disclosure and away from what might be considered superficial and distracting features.

Gating in face-to-face relationships:

  • Physical appearance and mannerisms tend to determine whom we approach.
  • We use available features to categorise potential partners.
  • In online relationships, there is an absence of these 'gates' that normally limit the opportunities for the less attractive, shy or less socially skilled to form relationships in face-to-face encounters.
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Absence of gating

Absence of gating and its consequences:

Barriers to interaction are not initially in evidence and so are less likely to stop potential relationships from getting off the ground.

  • A person's true self is more likely to be active in internet relationships than it is in face-to-face interactions. It is a contributor to the establishment of close relationships over the internet.

Zhao (2008): found that online social networks can empower 'gated' individuals to present the identities they hope to establish, but are unable to in face-to-face situations. The reduction of gating obstacles in the online environment also enables people to 'stretch the truth a bit' in their efforts to project a self that is more socially desirable than their real 'offline' identity. 

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Evaluation of gating

+ Supporting evidence - Zhao's study is up to date; in 2008.

- Self-report data - much of the evidence into the effect of absence of gating relies on self-report data, which may be prone to social desirability.

- Differing people - research does not eem to consider how the issue of gating may influence different groups of people, hence there may be gender or cultural bias in the application of the theory.

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Parasocial relationships

Parasocial relationships - an individual is attracted to another person, who is usually unaware of the existence of the person who has created the relationship.

  • One-sided.
  • A lot of emotional energy, interest and time spent on this person.
  • Usually towards a celebrity.
  • Illusion - something they'e created.
  • Complex set of emotions.

The target individual is unaware of the existence of the person who created the relationship.

These relationships may be appealing because they make few demands, and the individual does not run the risk of criticism or rejection as might be the case in a real relationship.

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Parasocial relationships

Parasocial relationships are more likely if:

  • The object of affection is perceived as attractive.
  • They are perceived as similar to us.
  • We perceive them as real.
  • The viewer is female.
  • The viewer is lonely and shy.

McCutcheon (2002) proposed the Absorption Addiction Model to explain how parsocial relationships become abnormal.

They have deficits in their own sense of personal identity. Absorption is an attempt to establish a personal identity. Absorption has addictive qualities, so individuals go to further and further lengths to maintain a sense of fulfilment via the parasocial relationship (enduring love).

This model therefore predicts that there will be an association between poorer mental health and the strength of parasocial relationships. 

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Celebrity Attitude Scale

  • Measures social aspects associated with celebrity worship.
  • Measures the intensity of a person's feelings towards the celebrity along with obsessions tendencies.
  • Measures the potentially harmful aspects of feelings towards the celebrity.

3 levels:

1. Entertainment-social: most people enjoy talking about celebrities and their lifestyles with their friends, and find this level of involvement in their ife interesting. 

2. Intense-personal: for some, a personal interest in one of these celebrities will intensify and may become obsessive. This may spark off a parasocial relationship as the individual feels an artificial closeness to the celebrity.

3. Borderline-pathological: in a small number of people, this interest in the celebrity develops even further and the behaviours associated with the relationship become abnormal and uncontrollable.

Introverted individuals are at higher risk for becoming addicted.

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Evaluation of parasocial relationships

+ Is there a link betweena PSR and loneliness? Lange: for some adolescents, an introverted nature, an especially difficult set of social circumstances and a lack of meaningful relationships may lead them to become increasingly 'absorbed' by the lives of these 'parasocial friends'. 

+ Is there a link between a PSR and mental health? McCutcheon: correlation between poor mental health and the stength of parasocial relationships.

- Self-report data - much of the research relies on self-report data, which could be unreliable and/or lack validity. Participants may feel uncomfortable admitting to what could be perceived by others to be an 'abnormal' relationship and so downplay their feelings or behaviour.

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