This paper explores the origins and underpinnings of the basic workplace motivational need of identity, as identified in the Integrated Model of Employee Engagement. It asks:
- Is identity, itself based in self-esteem (protection &/or enhancement), a “basic motivational need”?
- Is identity a culturally-derived, uniquely human “higher-order” construct without purpose other than supporting feelings of confidence and well-being?
- Does identity have a neural basis or home?
- How might varying levels & expressions of identity among employees influence “best-management”?
Klaus Grawe (1) identified basic human needs as intrinsic motivators of attention, effort and behaviour based on the previous works of others and the neuroscience that underpins them. Linking them to motivation schemas of approach (gain-orientation) and avoidance (loss-orientation), Grawe identified them as attachment, the pursuit of pleasure and avoidance of pain, self-esteem protection and enhancement, and orientation and control.
As compelling motivators that mostly influence emotions and actions at a non-conscious level, they are also the origin for the basic needs described in the Integrated Model of Employee Engagement. In that model:
Attachment is based in attachment theory (2, 3) and translates to Connection, as the parent-child bond can be argued to be less applicable in adulthood and in any case is impractical for workplace contexts. However, the need for close secure relationships remains through adulthood, typically following models learned in formative years (4). It is likely that the need for attachment, as it changes through maturity from an intimate and narrow child-parent bond to a broader social connection, is linked to identity, being how one fits in with, protects and is protected by larger, less stable and necessarily less uniformly intimate (5) social groups.
Orientation and control, relating to sense-making and the ability to influence people and events, especially one’s own actions and well-being (6, 7), translates to Empowerment, linked to the concepts outlined in Self-Determination Theory (8, 9) of preservation and enhancement of competence and autonomy. As a practical term, empowerment is descriptive of that need and a good check-question for managers, whose job must certainly be to empower their teams to perform, make good decisions and take on worthwhile and uncertain challenges.
There are broader implications for these concepts too. Control can be viewed as a micro-need (control over individual actions and events) and as a macro need (efficacy in meeting need fulfilment generally). Orientation can be linked to neural consistency – the matching of emotional/intuitive and cognitive/rational processing that drives our need for sense-making and supporting strongly held value and belief systems.
The pursuit of pleasure and avoidance of pain (1, 10, 11), being not doing what hurts (physically or psychologically) and doing things that are enjoyable, has been translated for a workplace context to Task Reward. In that context it leverages the same dopamine-based instant reward system and sees employees looking for enjoyment, stimulation, challenge and variety as sources for those fast rewards.
However, there is crossover into other areas – for example pursuing enjoyable interactions and avoiding distressing ones or feeling joy in empowerment compared to the distress of micromanagement or poor communication. This concept of crossover of needs is quite normal, sometimes in the same direction (e.g., enjoyment of a new task or challenge) and sometimes opposing (threats to feelings of competence in taking on a novel task or a new challenge, in turn creating the discomfort and indecision of neural inconsistency).
Self-esteem protection and enhancement is a need identified by Grawe and others (1, 12, 13) based on an assumption that it is a uniquely human need, but there is little evidence to support this. There is also a conceptual position to self-esteem that is of limited scope and helpfulness – that of self-esteem being an internal condition not dependent on, and resilient to, external criteria (14). Some have suggested that self-esteem is a complex human and cultural construction rather than a basic need (15), raising it to the level of being a higher order need that nonetheless can be as readily linked to the same motivational processes (the pursuit of congruence between need level and satisfaction and consistency in neural processing). In the Integrated Model of Employee Engagement, this need is the basis for Identity.
The motivation to maintain desired aspects of identity is self-esteem protection, whereas motivation to move toward a preferred identity is self-esteem enhancement. As with other needs, gaps between perceived and preferred identity are a source of incongruence, being motivation for change. Where that change is perceived to be unachievable, the uncontrollable incongruence created forms a social pressure that can lead to desperation, depression, self-harm, self-hate and suicide.
Misconceptions About Self-Esteem
That self-esteem is a distinctly human need.
There are some small problems evident in these theories of self-esteem, both relating to the purpose of this need being encoded, albeit as one that develops as an infant grows into childhood, in our DNA. As a Neolithic species living in danger-rich and nutrition-poor environments, homo sapiens ancestors could only survive in packs. A single human, one that was unable to form strong bonds (attachment), gain a core understanding of its environment or influence its own actions and safety through intuitive and cognitive processing, physical capacity and, over time language, (orientation and control), or to learn from experiences the things that threatened life (pain feedback via the nervous system) or supported thriving (the dopamine hits associated with high-energy foods), could simply not survive.
Further, the human pack, or tribe, like so many others, needs a structure to function and maintain order, allowing it to coordinate activities and draw on and multiply the sum of its parts to overcome foes and challenges. With language-enhanced coordination and the cognitive ability for complex imagining and planning, there was more scope for human children to be looked after by a community of carers, clothes-makers, cooks, hunters and defenders, each being a specialised role or task. For this level of coordination to work, each individual within the pack or tribe needed to know where they fit, including hierarchically, and what their specific role in a given situation was. Self-esteem is the process by which individuals understood themselves, with a wish for preservation or promotion for greater influence, entitlement and protection. This is where self-esteem is linked to identity, and identity to social place and purpose.
For pack species, to be cared for (survival), respected (increasing control and importance to others) and to pursue personal needs (survival of self and DNA) individual members seek to either maintain or increase their social acceptance and standing. In many species this can be seen in acts that create bonds such as social grooming (16) for acceptance and place, through to strength and aggression for power and breeding rights, and there are plenty of examples of this in human history as well. There is also more to it than either being a leader or a follower – for example, with wolves it is possible to identify the social place of pack members according to their order in a moving line. In humans it is also the case that while some compete for dominance and leadership roles, others prefer to find safety and security of place in popularity, peace-making, compliance, or perhaps in having a specific expertise valued by the group, and so gaining place without risking conflict.
With an evolutionary purpose of self-esteem as necessary for establishing, protecting and enhancing social position to improve chances of survival and passing on DNA, it is apparent that individuals in competitive pack species are also driven by this need. The link between self-esteem and survival through place and position within a pack ensures identity is a powerful primal hierarchical, competitive and unifying force that enhances the survival of individuals and the group. Simply, the idea that self-esteem is uniquely human (presumably because it is a “higher-order” need and we are a “higher-order” species) is unfounded and unhelpful.
That self-esteem can or should be internally-derived
The second problem is with the concept that self-esteem can or should be an internally-satisfied need. If so, it would have no evolutionary purpose other than to help some people feel slightly better about themselves, be more positive more often, and experience greater well-being (outcomes associated with high self-esteem (1)). And if that was self-esteem’s only purpose, the human race would have evolved to have inherently high self-esteem, and it wouldn’t be a motivator of behaviour, as it would be inherently satisfied. Further, if it served no real purpose, evolution dictates that it would have gone the way of tails and fur.
It is more realistic to view self-esteem in the social context it belongs, inevitably influenced by external feedback as a reward to be gained or loss to be avoided as a basic motivational influence. Nonetheless, where people have a strong favourable sense of self and are less affected by the feedback of others, internal (as against internally-derived) self-esteem is higher, supporting health and well-being. Through genetic variation and early childhood experiences some people have higher self-esteem needs than others, which may be linked to a drive for social status or a propensity for anxiety generally. But these factors don’t make self-esteem both internally generated and satisfied, they merely form a platform.
Rather than being seen as a source of weakness, the reliance of self-esteem on real and imagined social feedback is very useful. To ensure social acceptance, support and protection, it is important that an individual is a part of the group emotionally and actively. It is only through the loss of self-esteem that comes with embarrassment, guilt and shame about actions that are culturally unwanted or unacceptable that people feel driven to make amends for those things and avoid repeating them.
The act of desensitising oneself from feedback, or criticism only, is not a practical or helpful thing to do. By blocking all feedback we remove ourselves from the collective social consciousness, losing our ability to engage others as they lost their ability to engage with us. Engagement and empathy, essential for understanding and connection beyond spoken language (through brain wave synchronicity) is not a one-way-street (in therapy creating transference). Similarly, filtering feedback to allow compliments that support self-esteem but block criticism that might threaten it is, at best, narcissistic.
The distress that comes with feeling the disapproval of others, along with the euphoria that comes with receiving their approval, is a natural pain/pleasure guide to behaving and acting in ways that, for our ancestors, increased the chances of group inclusion, breeding, protection and survival. This primal emotional drive is no less strong now – arguably, it might be stronger. There is no evolutionary reason for self-esteem to be linked to pleasure and pain systems if it were to be internally-derived.
Identity Arising From & Maintained by Self-Esteem
Through early childhood experiences people form ideas of how they fit in, the affection and esteem they are held in by others, and the security of that esteem and security of social place and identity. Children believe the feedback they receive from attachment figures, power figures and peers in a simple and literal way – e.g., “you are smart/funny/fast/pretty/stupid/useless”. Children also have another challenge in how they “objectively” interpret and form memories around these early experiences – the immature hippocampus and an unformed cognitive capacity (through prefrontal cortex immaturity) exacerbate fantasies, errors and emotional factors to create memories, and pictures of self, that are inaccurate but strong.
Modifying these impressions later in life can be more difficult because they are likely to be held emotionally and “hard-wired” into core belief systems. For example, a child who was repeatedly praised for excellence and intelligence (e.g., “you are the smart one, you are perfect”) can easily form an identity of being knowledgeable and of perfectionism, and later in life, despite some recollections and understandings of the influence of those childhood experiences, still find it almost impossible to let go of that often unhelpful identity, for if they are not that, who are they?
Throughout life, feedback creates implicit and explicit memories that form a picture of oneself (17) through life experiences and how one fits into or out of different social environments largely based on emotional significance. Together they form a believed identity (those experiences felt true, so the sum of them must be true), which may be largely similar or dissimilar to a preferred identity and social place. This can be a problem though times of change as identities come and go. If the pretty girl at school loses her looks, who is she? If the sports star’s career is over, who is he? If the successful businessperson goes bankrupt, who is he or she? To close family and friends they may not have changed, but self-esteem and identity also relate to broader social roles and place, as they did tribally.
This series of events and their interpretations over a period can be described as autobiographical memory (18), creating an “autobiographical self” from the selectively felt, recalled and interpreted story of one’s own life. It has been defined as “the accumulated unique mental narrative that emerges from our experiencing and participating in the flow of events and interpersonal encounters that reach a level of awareness critically facilitated by emotional tone” (19) (p276). This occurs at both conscious and non-conscious levels (20-23), and, despite feeling true irrespective of objective truth, when interrogated can be, especially when accessible as explicit memory, fertile ground for reflection, therapy and helpful change.
Those life experiences typically create a reasonably coherent and favourable picture of one’s identity through combining conscious sense-making and non-conscious intuition (19). This favourable view is important, as it forms a platform for internally-derived self-esteem and gain-oriented view that supports optimism, resilience and well-being (24). However, it does not form without interpersonal interactions and is not immune to them. Further, while a favourable and coherent view of self is common (one has to be the hero in one’s own life story), it is often not an ideal view (the flawed hero?), so individuals seek to preserve and feel support for their current identity, and to bring it closer to the view of self they aspire to.
There are also likely to be gaps and ambiguities in how a person feels about themselves, with fears about perceived flaws and unknowns, seeing them act to hide things that might have them lose affection or social prestige – imposter syndrome (25) is an example of that. The linked emotions of shame and guilt are powerful as direct threats to self-esteem or internal identity (perhaps felt more as guilt) and social identity (perhaps felt more as shame). This concept of internal vs external identity, of who one believes one is versus how one believe they are seen by others and fit in with them, attempting to reconcile and satisfy both versions, along with errors in perception and often unrealistic aspirations, can be useful in understanding the complexity and confusion inherent in how self-esteem protection and enhancement is acted upon.
The idea that self-esteem or identity should be internally-derived states is not only flawed in terms of the evolutionary purpose of identity and the origins of how it is formed, stored and accessed, it is impractical. For example, extremely high internally-derived self-esteem suggests that when people are more resistant to the criticisms of others (as an attack on self-worth/identity), they must then also be less authentically open to external sources of identity confirmation, such as compliments, respect, appreciation and popularity. This insularity is unhelpful socially or in supporting self-esteem, disconnecting an individual from the people around them. Rather, it is not a matter of simply being resistant to the feedback of others, but of choosing how to most helpfully interpret and respond to it for personal growth and well-being as a member of that social system.
Certainly, a safe, positively focused childhood, therapy, mindfulness, reflective skills and meditation can all support higher internally-derived self-esteem, but, from early childhood through all life, self-esteem, and its partner identity, are more reliant on external than internal penalties and rewards. In this way, whilst a stable, reconciled and largely preferred identity can be largely maintained internally in ways that are resistant to threatening external feedback, it is impractical to assume self-esteem or identity are internally-derived states.
The Neural Home of Identity
The neural function responsible for forming and maintaining identity is autobiographical memory (19), which involves activation of hippocampus (dominantly left), superior frontal gyri, left angular gyrus, bilateral precuneus/posterior cingulate and lingual gyri, and left superior frontal gyri (26, 27). It also seems likely that vividly created, stored and recalled memories are likely to be associated with bilateral involvement of the hippocampus, in turn suggesting high levels of attention, emotional significance and processing (26). The disproportionate attention given to reward prediction error (27), part of the motivation and learning process (28) in turn biases memories of unexpected events or outcomes (29), in turn distorting identity.
Prior to 4 to 5 years of age, children struggle to encode events and place themselves within a timeline that is perceived and understood as a life continuum (30). From four to five years of age onward the emotional source and the knowledge of an experience can be attached to it as an organisation of events along a timeline (31, 32) – the basis for autobiographical memory. In evolutionary and biological terms development of the capacity for creating autobiographical memory, along with its role in forming a sense of self and place, is not necessary before this age due to the protective influence of high parental attachment and not possible due to immaturity of the brain regions involved.
Defining Identity as a Workplace Need
The workplace is a purposeful social system. While it is desirable for one or more very close, safe, virtually unconditional and trusting relationships to build within them, many modern workplaces aren’t inherently capable of facilitating them beyond being professional relationships – and fewer of prioritising them. This is due to a necessarily higher focus on task-oriented processes and outcomes than socio-emotional elements, with many “relationships” reduced to giving and receiving instructions, often not in-person. This reduces the scope for close interpersonal connection to be the basis of belonging, interpersonal safety and security within most workplace environments.
In turn, this elevates the need for personal orientation in relation to the various strata of social groups (work-groups, divisions, roles, associations, pay scales, regions etc), with place within smaller and larger groups being linked to identity. “I am an accountant / receptionist / manager / driver / a junior / a leader”. Not, “I perform the tasks of…”, or “My role is…”, but “I am…”.
As a “higher-order” (15) basic need, there are strong links to other basic needs. For example, identity through empowerment as competence, “I am a skilled and capable technician” and autonomy, “I am a trusted and respected technician”, and through both of these place and importance to the group. Or identity through connection, “I am popular, so must be worthy of being liked”. This also dispels the notion that intrinsic and extrinsic motivation and reward are mutually exclusive, for the feedback of others (a conditional extrinsic reward) is directly linked to identity and self-esteem (an intrinsic motivator).
Identity, through social place and value, is also linked to symbols, purpose and achievement. For example, “I work for Google” versus “I work for Joe’s IT repairs”, irrespective of role and skills. The clothes one wears, the brand of car one drives, the suburb one lives in, the people one mixes with – these are all symbols of social status that are closely linked to preserving or portraying a preferred identity.
The power of purpose, especially for outcomes that benefit others, speaks of identity as a caring, selfless person worthy of respect and appreciation – or of simply being liked (which is not to detract from altruism in comparison to socialites seeking to protect or enhance a preferred identity through associations with charitable events or acts). Purpose is a strong motivator linked to resilience that can overcome deficits in short-term rewards and is also closely linked to self-esteem / identity, if mostly at a non-conscious level. “I am worthwhile because what I am doing is worthwhile.” The opposite isn’t appealing.
Achievement in adulthood, as with childhood, is also a significant part of identity. Jackie Stewart? He’s the 3-time world champion driver. Barack Obama? He used to be president. Ed Sheerin? He’s the musician. People become defined by others as a simple, non-complex character based on what they’ve done as the strongest clue to who they are. Similarly, people are defined by witnessed behaviours. “He’s the trouble-maker”, “She’s the patient one”, “They’re all complainers”, irrespective that, as attribution theory would propose, those behaviours are more accurately a response to the situations people found themselves in at the time rather than an accurate insight into core identity or motivations (33).
Managing Identity in the Workplace
Bringing these ideas closer to the workplace, research has shown that the most common want from employees to their leaders is that they share an inspiring vision of a preferred future (34) as a unifying motivator of positive focus and discretionary effort. The link with purpose here is clear, and, by inference, the links with identity as a contributor, through personal effort, to that preferred future. The more effort an individual makes toward achieving a worthwhile goal, especially with immediate or long-term social implications, the more rewarding that effort inherently is.
Our assessments have shown that identity enhancement, through self-esteem, purpose and place, is valued by employees, with substantial implications for retention, engagement, behaviour and performance. And while there is a definite preference for sincere recognition and appreciation, there is also comfort with receiving honest, fair negative feedback delivered in a reasonable way, especially when there is a distinction between the person and the action. The employee isn’t the problem, the decision, behaviour or performance is. This allows for corrective conversations that are open, honest and focused on solutions more than blame or personal attack. The flip side is of course that a similar approach is helpful for compliments – if the behaviour is complimented it is more likely to be repeated, and the employee, now motivated to hear it again, understands that it is conditional upon repeating the behaviour, creating reward anticipation that enhances future motivation.
The identity need is not felt equally by all employees. For those who require lower or fewer identity-related rewards, there is also likely to be lower identity-related motivation. This may be a part of an overall lower-energy motivation/reward schema, or it might be that they find meaningful fulfilment in others ways (e.g., through enjoying their work tasks alone). Employees like these are less likely to look for compliments or recognition, so are less likely to do things that are rewarded by them (e.g., personal standards rather than meeting organisational requirements, or not giving discretionary effort to help others).
For employees with high identity need levels, employers can expect some “neediness” around attention, compliments and social position, but high effort and attention given to acts perceived to be linked to them. The extra effort available from making those rewards available makes a good case for managers to offer and leverage those rewards to draw on and channel that available motivation. Where a manager finds an employee’s demands for attention and respect too high, the response from the employee cannot be to simply require less. Rather, they will seek that attention, and at times power, in other ways, including undermining and challenging managers. It is highly likely that “Trouble-makers”, “agitators” and “difficult” employees are mostly responding to threats to their preferred identities through their actions, both in finding and asserting power for social position, and challenging the individuals and institutions that, through a bias toward criticism or simply being ignored, they perceive to have threatened or harmed them.
Identity, based largely in self-esteem and purpose, is a personally-constructed reality arising from memories and a need for social place. Although a higher-order need, it is necessary for the efficient functioning of complex mammalian social groups and, as a strong driver of behaviour and well-being, can only be considered a basic need, despite its status – or perhaps practical flexibility, as a construct. Certainly there is a basic drive for identity in all humans that sees competition for social status as a powerful motivational force for much discretionary effort and spending, both linked to its reward.
In the workplace, there is little doubt that identity is highly influential. Irrespective of ideas that self-esteem can be or should be internally-derived, in the workplace sincere compliments are a valued motivator and reward that can only be linked to self-esteem and identity, just as criticisms are taken hard. The want of a career is all about social status, and even rates of pay are linked to self-esteem – that one person gets paid more than another can only be a reflection that their efforts are more valuable, that they are a more valuable asset to the team, or perhaps society, that they are more worthy, that they are better. Where an employee is demoted, the loss of self-esteem is an attack on identity within that social context, typically leading to disengagement and detachment, and commonly resulting in resignation.
The high-maintenance employee is more demanding, and riskier in retribution, but also has the most potential if an organisation and manager can fulfil their higher needs through productive actions and behaviours. As an employer, manager or leader, offering employees simple and accessible pathways to protect and enhance self-esteem, and so consolidate identity or shift closer to a preferred one, is a simple and effective facilitator of effort, engagement and well-being that comes with little or no cost other than the time, attention, inclusion and recognition that employees are looking for in return.
Author: Michael McIntosh (2019) [email protected]
- Grawe K. Neuropsychotherapy. New York: Psychology Press; 2007.
- Bowlby J. Attachment and loss. New York, NY: Basic books; 1973.
- Bowlby J. A secure base: Parent-child attachment and healthy human development. New York, NY: Basic books; 1988.
- Badenoch B. Being a brain-wise therapist: A practical approach guide to interpersonal neurobiology. New York, NY: Norton; 2008.
- Dunbar RIM. Phoning home: keeping in touch with social networks. British academy centenary project. [Lecture Presentation]. In press 2015.
- Powers WT. Behaviour and the control of perception. New York, NY: Aldine; 1973.
- Epstein S. Cognitive-experiential self-theory. In: Pervin LA, editor. Handbook of personality: Theory and research. New York, NY: Guilford; 1990. p. 165-92.
- Deci EL, Ryan RM. The “what” and “why” of goal pursuits: Human needs and the self-determination of behavior. Psychological inquiry. 2000;11:227-68.
- Gagne M, Deci EL. Self-determination theory and work motivation. Journal of organisational behaviour. 2005;26:331-62.
- Epstein S. Integration of the cognitive and psychodynamic unconscious. American psychologist. 1994;49(8):709-24.
- Freud S. Beyond the pleasure principle. New York, NY: Norton; 1959.
- McDougall W. An introduction to social psychology. London: Methuen; 1936.
- Becker E. The birth and death of meaning: An interdisciplinary perspective on the problem of man. 2nd ed. New York, NY: Free Press; 1971.
- Trzesniewski KH, Donnellan MB, Robins RW. Development of self-esteem. In: Zeigler-Hill V, editor. Self-Esteem. Florence, KY: Psychology Press; 2013. p. 60-79.
- Dahlitz MJ, Rossouw PJ. The consistency-theoretical model of mental functioning: Towards a refined perspective. In: Rossouw PJ, editor. Neuropsychotherapy: Theoretical underpinnings and clinical applications. Brisbane, AU: Mediros; 2004.
- Dunbar RIM. Grooming, gossip and the evolution of language. London, UK: Faber and Faber; 1996.
- Jungert M. Memory, personal identity, and memory modification. In: Raniisch R, Rockoff M, Schuol S, editors. Selbstgestaltung des Menschen durch Biotechnologien. Tübingen: Francke; 2015. p. 129-40.
- Robinson JA. Autobiographical memory. In: Gruneberg MM, Morris P, editors. Aspects of memory. 1. 2nd ed. London: Routledge; 1992.
- Blinder BJ. The autobiographical self: Who we know and who we are. Psychiatric annals. 2007;37(4):276-84.
- Damasio AR. The feeling of what happens: Emotion, reason and the human brain in the making of consciousness. New York, NY: Harcourt-Brace; 1999.
- LeDoux JE. The self: Clues from the brain. Annals of New York Academy of Science. 2003;1001:101-6.
- LeDoux JE. Synaptic self: How our brains become who we are. New York, NY: Viking; 2002.
- Debree J, LeDoux JE. From self-knowledge to a science of self. Annals of New York Academy of Science. 2003;1001:305-16.
- Williams EF, Gilovich T. Do people really believe they are above average? Journal of experimental psychology. 2008;44(4):1121-8.
- Sakulku J, Alexander J. The imposter phenomenon. International journal of behavioural science. 2011;6:73-92.
- Armelle V, Pascale P, Desgranges B, Chetelat G, Lebreton K, Landeau B, et al. Hippocampal activation for autobiographical memories over the entire lifetime in healthy aged subjects: an fMRI study.: Lifelong autobiographical recollection. Cerebral Cortex. 2007;17(10):2453-67.
- Piolino P, Desgranges B, Hubert V, Bernard FA, Matuszewski V, Chetelat G, et al. Reliving lifelong episodic autobiographical memories via the hippocampus: A correlative resting PET study in healthy middle-aged subjects. Hippocampus. 2008;18:445-59.
- Schultz W. Dopamine neurons and their role in reward mechanisms. Current opinion in neurobiology. 1997;7:191-7.
- Kim SI. Neuroscientific model of motivational process. Frontiers in Psychology. 2013;4.
- Berridge KC, Kringlebach ML. Pleasure systems in the brain. Neuron. 2015;86:646-64.
- Povinelli DJ, Simon BB. Young children’s understanding of briefly versus extremely delayed images of the self: Emergence of the autobiography stance. Developmental Psychology. 1998;34(1):188-94.
- Neisser U. The roots of self-knowledge: Perceiving self, it and them. Annals of the New York Academy of Sciences. 1997;818:18-33.
- Perner J, Lang B. Development of frame of mind and executive control. Trends in cognitive science. 1999;9:337-44.
- Myers DG. Exploring social psychology. 7 ed. New York, NY: McGraw-Hill.
- Kouzes MK, Posner BZ. The leadership challenge. 4 ed. San Francisco, CA: Jossey-Bass; 2007.