Humans are able to accomplish great projects by forming heterogeneous and complementary teams in terms of skills, knowledge and behavioural competencies. Studies show cohesiveness is an important characteristic of high-performing teams and underline the existing positive correlation between cohesion and performance, especially when it comes to project management teams. 
Cohesiveness is the strength and extent of bonds between members of a same team. It determines the motivation of team-mates to remain in the team and achieve the common goal. Due to its worthiness, it is of great relevance for leaders and project managers to understand how to create and promote cohesion in their teams. Cohesiveness is multidimensional, therefore needs time to be developed and it is more likely to occur in small size teams. Further on, a more comprehensive definition of cohesiveness is given, as well as actions to take in order to promote cohesion in a team.
Although team cohesiveness is a crucial aspect in teams that reach high performances, it would be a mistake for team leaders to focus only on this single aspect. A number of other factors equally important contribute to the performance of a team, two of the aspects are briefly mentioned in the end.
Meaning and Importance of Cohesion
Nowadays project teams are largely employed in many different industries, in change management projects within organisations and in education as well. The major advantages of teams are the diversity in knowledge and ideas and, if the team is in good sync, the ability to be more effective and efficient than a single person. Psychological aspects have been identified as key elements of project success and efficacy, in particular, it exists a positive correlation between team cohesion and team performance.  Cohesion fosters motivation among team-mates and allows coordination, increases creativity and allows a more freely exchange of knowledge and expertise. 
According to the Merriam-Webster dictionary, cohesion is “the act or state of sticking together tightly”.
At first, team cohesion researchers presented cohesion as a unidimensional characteristic of high-performing teams referring to it as “a field of forces making group members stay together”.  The unidimensional description was too vague to convert it in a measurable characteristic, therefore a new multidimensional description was adopted. The most common one is tridimensional and includes:
• “Social cohesion” that refers to interpersonal attraction between team-mates, interest in other’s company, time spent together and friendship or closeness;
• “Task cohesion” that reflects the shared commitment of a team to a certain task or goal and the motivation to coordinate team efforts to achieve goals;
• “Group pride”, a dimension studied mostly in sport teams.
Since it takes time to create meaningful bonds, one of the most relevant factors that influences cohesion is the time spent together.
A Practical Method to Achieve Cohesion
Cohesion and leadership styles
Leadership styles are to be taken into consideration by team leaders trying to promote cohesion in a team. “Supportive leadership” has a positive effect on team cohesion regardless of the cultural context, while “directive behaviour” has a negative effect, especially in individualistic cultures.
A leadership style associated with “directive behaviour” is the transactional leadership, a style focusing on results and highly relying on systems of rewords and penalties. A transactional leader allows the team members to freely perform as the members see fit, only intervening when problems occur. On the contrary, “supportive behaviour” is associated with transformational leadership, a style that focuses on individuals, social systems and long-term goals instead of short-term ones. Transformational leaders develop motivation and morale in teams and are viewed as charismatic and visionary. 
According to Shmuel Stashevsky and Meni Koslowsky, transformational leadership was founded to be associated with higher levels of team cohesiveness when compared to transactional leadership. Leaders willing to achieve cohesion should adopt a transformational leadership style in order to build a team of individuals who can work well together for a common goal. 
Cohesion in Tuckman’s five stages of team development
In 1965, based on previous research, Tuckman postulated that teams go through five stages of development: forming, storming, norming, performing and adjourning. The stages start from the time that a group first meets until the project ends. According to Tuckman, cohesion occurs during the third stage of team development namely the “norming” stage. At this point, the concept of team as a functioning whole is forming. The team is finding its own language, rules and is building on cohesion.  Norms are more likely to be accepted and followed if the level of cohesiveness is increasing.  Members are concern with integration and maintenance of relationships. During this stage several tendencies may occur:
• Understanding the common grounds between team-mates;
• Increasing friendship networks;
• Increasing role interdependence;
• Increasing involvement, harmony and solidarity;
What leaders and team-members can do to foster cohesion is understanding the relevance of all stages of team development, what problems can occur in each stage and how to cope with them. During the storming stage there is a lack of cohesion, but at the same time the team is paving the way to achieve it. It is important for managers to understand that successfully overcoming the storming stage is essential to reach the norming stage and then the performing stage. In this phase the leader should focus on shifting the attention of the team from personal frictions to the team goals and clarifying roles, while at the same time adopting a coaching mindset and help team members throughout conflict resolution.  At the time the team is transitioning from the storming stage to the norming stage, the team-leader should facilitate the process of creating norms and provide more autonomy to the team-members so they can take more responsibility.
Other key aspects that enhance team cohesiveness
Emotional intelligence is “a form of social intelligence that involves the ability to perceive and express emotions, to understand and use them, and to manage emotions so as to foster personal growth”. 
In literature, emotional intelligence consists of different competencies grouped into four clusters:
• Self-awareness – understanding own emotions in the moment and use the understanding as a guide in the process of taking decisions.
• Self-management – handling emotions in a way that facilitate goal achievement rather than interfere and recovering from stressful emotions.
• Social awareness – understanding other people emotions and being able to stand in their shoes.
• Social skills – handling emotions in relationships and being able to persuade, negotiate and lead for cooperation. 
Janine Black, Kihwan Kim, Shanggeun Rhee, Kai Wang and Sut Sakchutchawan found that team cohesion is higher in teams where team-mates demonstrate grater command of emotional intelligence skills.  According to Brigette Ann Rapisarda, nine out of thirteen competencies were correlated with team cohesiveness, namely achievement orientation, empathy, influence, communications, leadership, conflict management, self-control, adaptability, and building bonds. Most of these capabilities concern social awareness and skills. On the other hand, among previous mentioned capabilities, only achievement orientation and empathy are correlated with performance.  In order to build team cohesiveness, team-members have to develop emotional competencies as a whole throughout tailored trainings and norms that strengthen trust. 
Trust and conflicts
In a study held in Malaysia, team trust was found to predict team cohesion, team satisfaction and project team effectiveness.  Team building activities promote trust in a team and such activities can be organised outside work hours and location. In the beginning it is important to let team members get to know so they can find what they have in common as persons and workers. At this stage, a useful tool to use as a starting point of deeper sharing sessions is represented by MBTI. Being curious and not judgmental are two important factors that allow trust to form. The leader of the team should always promote respect among team-members and encourage open and not judgmental discussions about occurring issues during the lifetime of a project, as well as good practices in giving and receiving feedback.  Creating a safe space allows to tackle conflicts in a more constructive way instead of eventually avoiding heavy emotions among team-mates. Address conflicts when they arise is fundamental to let the team focus on the project goals. 
Time and size of a team
It takes time to get to know and appreciate each other’s skills in a team, as well as to form meaningful bonds and to build trust and cohesiveness. Unfortunately, this is an aspect in contrast with the nature of projects that are limited in time. Moreover, the bigger the team is, the more time will take.  Small groups tend to be more cohesive since members have a greater degree of face-to-face communication, it is easier for them to find common ground and agree on different decisions and is more unlikely that undermining-cohesion-cliques will form over time.
Team agreements, organisational structures and processes
According to PMI book, team agreements, organisational structures and processes are fundamental factors to take into consideration when creating a collaborative project team environment and therefore a cohesive team. In regard to team agreements, refer to the section “Cohesion in Tuckman’s five stages of team development”. Organisational structures are the relations occurring between elements of project work and organizational processes and they may concern about roles, functions and authority. In order to coordinate efforts, teams make use of pre-existing structures or form new ones. “Definition of roles and responsibility” is an example of organisational structure, for instance, clarity in this type of definition improves team culture since specific tasks can be delegated to single members or a group of specific members. An example of roles and responsibilities to delegate can be authority, accountability and responsibility. Processes are defined by teams to complete the tasks and assignments. In doing so, project teams are influenced by the organisational culture, the nature of the project and the environment. Promoting inclusiveness and collaborative environments helps knowledge and expertise sharing among team members. 
Cohesiveness is just One Aspect
Cohesiveness research limitations
In seventy years, much research has been conducted regarding the relationship between cohesiveness and performance, but experts, psychologists and theorists are still debating about it. Much of the debate is around inconsistencies in definitions and classifications in types of teams across papers.  The other consistent body of debate goes around differences in results: some researchers found out that cohesiveness might not be positively correlated with high performance or that cohesiveness is critical, but not always predicts effectiveness and high performance. Other researchers found out that the relationship is stronger in correlational studies rather than in experimental studies and in real groups rather then artificial.  The research on cohesion still leaves room for improvement.
Other aspects concurring in the creation of high-performance teams
For team leaders and project teams, building cohesiveness is relevant to create a collaborative mindset and achieve high performance, but at the same time cohesion should not become the only aspect to focus on. For example, team performance has found to be function of the knowledge level of team members.  Other findings affirm that teams should specifically have strong performance norms together with high cohesiveness levels in order to avoid social loafing and achieve high performance.  More on project teams and performance can be found in “High performing teams”.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 François Chiocchio, Hélène Essiembre. ‘’Cohesion and Performance A Meta-Analytic Review of Disparities Between Project Teams, Production Teams, and Service Teams.’’ Small Group Research Volume 40 Number 4 (2009) https://journals.sagepub.com/home/sgr
- ↑ 2.0 2.1 2.2 2.3 Shmuel Stashevsky and Meni Koslowsky Bar-Ilan. University, Ramat Gan, Israel. ‘’Leadership team cohesiveness and team performance.’’ International Journal of Manpower Vol. 27 No. 1, 2006 pp. 63-74 https://www.emerald.com/insight/publication/issn/0143-7720
- ↑ Hein Wendt, Martin C. Euwema, I.J. Hetty van Emmerik. ‘’Leadership and team cohesiveness across cultures.’’ The Leadership Quarterly 20 (2009) 358–370 https://www.researchgate.net/publication/284640336_Leadership_and_team_cohesiveness_across_cultures
- ↑ 4.0 4.1 Bruce W. Tuckman. ‘’Developmental Sequence in Small Groups.’’ Classics for Group Facilitators. Psychological Bulletin, Volume 63, Number 6, Pages 384-99 http://www.communicationcache.com/uploads/1/0/8/8/10887248/developmental_sequence_in_small_groups_-_reprint.pdf
- ↑ 5.0 5.1 5.2 ER Services, Principles of Management ‘The Five Stages of Team Development’’ https://courses.lumenlearning.com/suny-principlesmanagement/chapter/reading-the-five-stages-of-team-development/
- ↑ 6.0 6.1 ‘’Stages of team development.’’ https://toggl.com/track/stages-of-team-development/
- ↑ 7.0 7.1 7.2 7.3 Brigette Ann Rapisarda, Florida International University. “THE IMPACT OF EMOTIONAL INTELLIGENCE ON WORK TEAM COHESIVENESS AND PERFORMANCE.’’ The International Journal of Organizational Analysis 2002, Vol. 10, No. 4, pp. 363-379 https://www.emerald.com/insight/content/doi/10.1108/eb028958/full/html
- ↑ Janine Black, Kihwan Kim, Shanggeun Rhee, Kai Wang and Sut Sakchutchawan School of Management and Marketing, College of Business and Public Management, Kean University, Union, New Jersey, USA. “Self-efficacy and emotional intelligence Influencing team cohesion to enhance team performance.’’ (2018) www.emeraldinsight.com/1352-7592.htm
- ↑ 9.0 9.1 9.2 9.3 ISIXSIGMA. ‘HIGH-PERFORMANCE TEAMS: UNDERSTANDING TEAM COHESIVENESS.’’ ] https://www.isixsigma.com/implementation/teams/high-performance-teams-understanding-team-cohesiveness/
- ↑ Han-Ping Fung. “RELATIONSHIPS AMONG TEAM TRUST, TEAM COHESION, TEAM SATISFACTION AND PROJECT TEAM EFFECTIVENESS AS PERCEIVED BY PROJECT MANAGERS IN MALAYSIA.’’ International Journal of Management and Sustainability, 2014, 1(1): 1-15 http://pakinsight.com/?ic=aimandscope&journal=62
- ↑ Management Institute. “THE STANDARD FOR PROJECT MANAGEMENT’’ Section 3 (2021) https://www.pmi.org/pmbok-guide-standards/foundational