# Coaching evidence base

This file holds the cited research that grounds the skill. When the document
includes an evidence note, draw the figures and claims from here. Cite authors
and years in the document body so the practitioner can trace provenance.

## Does coaching work (effect sizes)

- **de Haan and Nilsson (2023)**, meta-analysis of randomized controlled trials
  only (39 samples, N = 2,528): overall standardized effect of workplace coaching
  g = .59, moderate range. Some publication bias noted. Mechanism proposed:
  coregulation between coach and coachee.
- **Wang, Lai et al. (2022)**, meta-analysis of psychologically informed coaching
  approaches: especially strong effects on goal attainment (g = 1.29) and
  self-efficacy (g = 0.59). Effects on objective, other-rated performance were
  larger than on self-rated performance.
- **Jones, Woods and Guillaume (2016)**: workplace coaching produced a moderate
  positive effect on performance (d = 0.36), stronger when explicit coaching
  frameworks were used. Structured approaches outperform unstructured ones.
- **Theeboom et al. (2014)**: positive effects across individual-level outcomes
  (performance, well-being, coping, work attitudes, goal-directed self-regulation).
- **Integrative vs single method:** integrative methods (g = 0.71) outperformed
  single-method coaching (g = 0.45). This is the empirical warrant for the skill's
  integrative, multi-framework stance rather than betting on one model.

## How coaching works (the active ingredients)

- **Working alliance.** Graßmann, Schölmerich and Schermuly (2020), meta-analysis
  of 27 samples (N = 3,563): a high-quality working alliance relates to client
  outcomes at r = .41 (moderate, consistent), positively related to all desirable
  outcomes (range r = .32 to .64, strongest for affective and cognitive outcomes)
  and negatively related to unintended negative effects (r = -.29). The alliance
  has three parts (Bordin): the bond, agreement on goals, and agreement on tasks.
  Implication: contracting and relationship-building are the highest-leverage early
  moves, not preliminaries to rush through.
- **Self-efficacy** is both an outcome and a mechanism: alliance and goal progress
  raise self-efficacy, which sustains behavior change.
- **Coachee motivation and autonomy** moderate everything downstream. Where
  intention or motivation is low, technique-only interventions (for example
  implementation intentions) have weak effects.

## The engines of change

### Goal-setting theory (Locke and Latham)

- Specific, difficult, accepted goals beat vague or "do your best" goals. Effects
  run through attention, effort, persistence, and strategy development.
- Boundary conditions that matter for coaching:
  - Difficulty is relative to the individual's current capability.
  - Goals must be paired with feedback on progress, or the effect collapses.
  - For novel or complex tasks early in skill acquisition, a hard specific outcome
    goal can backfire by crowding out the strategy development the person still
    needs. Use a learning goal (acquire and apply a strategy) rather than an
    outcome goal in that case.
- Outcome vs performance vs process goals: break large outcomes into performance
  and process goals to keep them controllable and motivating.

### Self-determination theory (Deci and Ryan)

- Durable motivation depends on autonomy, competence, and relatedness. Externally
  imposed goals without buy-in tend to fade once pressure is removed.
- Coaching implication: the coachee co-authors the goal; the coach supports
  autonomy rather than prescribing.

### Implementation intentions and mental contrasting (Gollwitzer; Oettingen)

- Implementation intentions are if-then plans: "When situation X arises, I will do
  Y." They link an anticipated cue to a goal-directed response and help close the
  intention-behavior gap.
- Effects are larger for simpler behaviors and when motivation is already present;
  smaller and slower for complex multi-step behaviors, where they may need
  reinforcement.
- Mental contrasting (imagine the desired future, then confront the present
  obstacle) builds commitment and pairs well with implementation intentions. The
  combined protocol is taught as WOOP (Wish, Outcome, Obstacle, Plan).

### Immunity to Change (Kegan and Lahey)

- Behind a stubborn behavior often sits a hidden competing commitment, and beneath
  that a big assumption: a belief, usually untested, about what would happen if the
  person changed. Together these form a psychological immune system that protects
  the status quo.
- The four-column map: (1) improvement goal, (2) what I do or do not do that works
  against it, (3) the hidden competing commitment and the worry behind it, (4) the
  big assumption. Change proceeds by designing safe tests of the big assumption.
- Use as a reflective lens with professional coaches/facilitators as the readers,
  which is the case for this skill. Critically, the competing commitment and big
  assumption are surfaced BY THE CLIENT, through the coach's questioning. The
  document offers them only as hypotheses for the coach to explore, never as
  conclusions to present to the client. A coach who hands a client a pre-written
  competing commitment has done the client's insight work for them, which is poor
  practice. Frame every item as something to explore, test, or invite, not assert.

## Teams

- **Psychological safety** (Edmondson): a shared belief the team is safe for
  interpersonal risk-taking. Google's Project Aristotle found it the strongest of
  five factors predicting team effectiveness. But evidence (for example Koodamara
  et al.) shows it often works indirectly, through team learning behavior and team
  efficacy, rather than directly on performance. Build it early; it is the
  precondition for the rest of the team work.
- **Hawkins' Five Disciplines** of high-performing teams (the five Cs):
  Commissioning, Clarifying, Co-creating, Connecting, Core Learning. Used as the
  backbone for the team session arc.
- Team coaching effect: emerging evidence (for example Jones et al.) finds team
  coaching can be highly effective and, when the leader is included, can lift
  leadership behavior across the team. Evidence base is younger than for
  individual coaching, so state team claims with appropriate humility.

## How to use the evidence in the document

- One tight evidence note near the front, with author-year citations.
- In the document body, express findings in plain language and name the source, but
  lighten the numeric precision. Prefer "a moderate, reliable effect" or "one of the
  strongest predictors" over quoting exact decimals like r = .41 or g = .59. Keep the
  precise figures in this reference file for the author's own grounding; the body is
  for practitioners, not a literature review.
- Add one short line acknowledging that these are average effects across many people
  and contexts, not guarantees for any one client. This is more defensible and ages
  better.
- Translate effect sizes into plain meaning for a practitioner (for example "the
  coach-coachee relationship is one of the most reliable predictors of whether
  coaching works, so the early sessions invest in it deliberately").
- Keep statistical symbols in italics (r, g, d) if exact figures are ever used; no
  other italics.
- Never overclaim. Coaching effects are real and moderate, not guaranteed. The
  disclaimer still governs.
