The M&A Bias Nobody Underwrites: The Illusion of Control
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Every deal model has a synergy line. No deal model has a "we don't actually run this company yet" line. That gap is where the illusion of control lives — and it is the single most expensive bias in M&A.
What the illusion of control actually is
The illusion of control was defined by Harvard psychologist Ellen Langer in 1975 as "an expectancy of a personal success probability inappropriately higher than the objective probability would warrant" (Langer, Journal of Personality and Social Psychology). In her experiments, people who chose their lottery ticket, or who competed against a nervous opponent, or who were actively involved in a task, priced their odds of winning far above the true probability — even though the outcome was pure chance.
Langer identified four "skill cues" that trigger the illusion even in random environments: choice, competition, familiarity, and active involvement (Wikipedia summary of Langer's research).
Look at any M&A process. It is a machine for manufacturing all four cues simultaneously.
Why M&A is the perfect trap
An acquisition process is designed — literally engineered by advisors, bankers, and internal deal teams — to make the buyer feel in control:
· Choice. You picked this target off a long list. You said no to others. The very act of selection convinces you the outcome now depends on your judgment.
· Competition. Auctions, stalking horses, "there's another bidder in the room." Competitive processes are the strongest skill cue Langer identified — and the one bankers rely on most.
· Familiarity. Weeks of data room review, management presentations, expert calls, site visits. You know this business now. Except you don't — you know its data room.
· Active involvement. You built the model. You negotiated the SPA. You wrote the 100-day plan. The plan feels like control. It isn't.
The result is a systematic overestimation of the acquirer's ability to bend post-close outcomes — synergies, retention, integration timelines, cultural fit — that are, in large part, not under the acquirer's control at all.
The empirical footprint
This isn't abstract psychology. It shows up in the data.
· Majority of M&A deals fail to create shareholder value, measured by post-deal stock underperformance, synergy shortfalls (less than 70% of projected synergies realized within 2–3 years), or divestiture within five years (Acquisition Stars review of failure rates). HBR has published the same range for decades (Harvard Business Review, "Don't Make This Common M&A Mistake").
· CEO overconfidence destroys value in M&A. A study of 237 Russian M&A deals from 2005–2019 found that CEO overconfidence — closely related to the illusion of control — is significantly associated with value destruction, while good corporate governance partly mitigates it (HSE working paper on cognitive biases and M&A performance).
· Roll's hubris hypothesis (1986) — the foundational finance paper on this — argued that acquirers systematically overpay because they believe their valuation is right and the market's is wrong. It is the illusion of control dressed in a DCF.
Langer's own follow-up work is even more uncomfortable for dealmakers: the illusion is stronger the more involved and invested the decision-maker is (PMC review, "Illusion of Control: The Role of Personal Involvement"). In other words, the partner who has lived on the deal for nine months is the least able to judge whether it will work.
Where the illusion hides in the deal lifecycle
The bias doesn't appear once. It compounds at every stage.
Sourcing and screening. "This is a proprietary opportunity." Proprietary implies choice, which implies control. In reality, proprietary deals often mean "no one else wanted it enough to run a process."
Valuation. Synergy models are the purest expression of the illusion. Every synergy line is a claim that the acquirer will cause an outcome that the standalone target cannot. Cost synergies at least have a physical basis (headcount, real estate, contracts). Revenue synergies are almost entirely illusion — they assume the acquirer controls customer behavior, sales-force incentives, and cross-sell adoption on Day 366.
Due diligence. DD is a familiarity machine. The more red flags you close out, the more you feel you understand the target. But diligence surfaces the known unknowns. It cannot surface the unknown unknowns, and those are the ones that kill deals post-close.
Negotiation. Winning an auction is a skill cue par excellence. The winner's curse is not just a pricing problem; it is a cognitive one. The bidder who wanted it most is, by definition, the one whose illusion of control was highest.
Integration planning. The 100-day plan feels like a lever. Often it is a schedule of things that will happen to the integration team rather than because of it. Key talent leaves on their own timeline. Customers churn on theirs. Regulators approve on theirs.
What to do about it — practical debiasing for deal teams
You cannot eliminate the illusion of control. Langer's findings suggest the cues that trigger it are baked into how humans process agency. But you can build countermeasures into your process.
1. Separate the people who fell in love from the people who underwrite. The deal captain should not also be the final approver. Anyone who has been personally involved for months has, by construction, the highest illusion of control on the team. Use a fresh IC or a pre-mortem panel that has not worked the deal.
2. Underwrite the base rate, not the story. Before running your synergy model, write down: "For deals of this size, in this sector, with this deal structure, what percentage historically hit their synergy case within 24 months?" The reference-class forecast is almost always harsher than the bottom-up plan. If your plan is materially better than the base rate, name the specific, verifiable reason — or discount it.
3. Pre-mortem the deal in writing. Two years from now, this deal is a disaster. Write the post-mortem now. What went wrong? Which assumptions failed? Which levers turned out not to be levers at all? The pre-mortem is the single cheapest, most effective control on the illusion of control.
4. Distinguish "things we can cause" from "things we can only hope for." For every value driver in the model, tag it: controllable (cost takeout under our authority), influenceable (customer retention where we can act but not decide), or chance (regulatory approval, macro, competitor response). Sum the value assigned to each category. If more than half the value sits in "influenceable" or "chance," the deal is a bet, not a plan — price it that way.
5. Kill revenue synergies in the price you pay. Pay for cost synergies, which you largely control. Get revenue synergies for free. Every practitioner knows this rule. Almost no one follows it under competitive pressure — which is exactly when the illusion is strongest.
6. Institutionalize the disconfirming question. Assign someone the explicit job of arguing against the deal at every gate. Not as devil's advocate theatre — as a scored, documented role. Langer's cues are triggered by consensus and involvement; disconfirmation is the antidote.
The bottom line for M&A professionals
The illusion of control is not a character flaw. It is a structural feature of how deal processes are built. Auctions, diligence, models, and integration plans all manufacture the feeling of agency — which is precisely why acquirers overpay, oversynergize, and underdeliver.
The best acquirers I have seen in the DACH mid-market don't debias by being smarter. They debias by being humbler about the boundary between what they can cause and what they can only hope for. Everything on the "hope for" side of that line gets a discount, or it doesn't get paid for at all.
That single discipline — pricing the deal you actually control, not the deal you feel you control — is worth more than any diligence tool, any AI model, and any playbook. It is the closest thing M&A has to an edge.
Dr. Karl Michael Popp is an M&A expert and author specializing in software company acquisitions.Contact: +49 6202 5829917 | www.drkarlpopp.com
Parts of this blog might be AI generated
