Risk Perception


Risk is something we all need to assess from time to time. The problem lies in how we do it. If there are factors we fail to take into account that affect our risk perception then our evaluation may as likely be wildly unrealistic, as appropriate. Emotion tends to skew things in one direction or other, as does as the degree of perceived asymmetry between the benefits and dangers –if we really desire or enjoy something, we might be less risk averse than if we were not keen on it in the first place. The status or acceptance acquired from smoking for a teenager, say, might counterbalance the long-term dangers; it might not be seen that way by an older, more confident adult. And immediately experienced risk –driving a car with faulty brakes- may be more influential than future risk such as lifestyle changes for cardiac disease prevention. And then, of course, there are cognitive biases –our own subjective mythologies, expectations and intuitions- not to mention cultural biases, all contributing to the overall assessment of the acceptability or not of the risk.

But I suspect that a major obstacle in risk perception lies in its probabilistic nature. People have enough difficulty in understanding the simple Bell Curve distribution of likelihood let alone the mathematical Baye’s theorem which ‘describes the probability of an event based on conditions that might be related to the event.’ Our estimates are more intuitively driven than statistically. Understandable, to be sure, but unreliable in most appraisals. Misleading. Dangerous, even.

It’s hard to grasp the concept that even doubling a risk when it is almost imperceptably low already, still leaves it almost imperceptable. So, at what stage does it become unacceptable, if it wasn’t really perceived to be that in the first place? Is any risk acceptable if we know about it, no matter how small and unlikely? What about the background risks that are inherent in most things –be they visible and published or not? Riding a bicycle, for example, or running on a treadmill, walking to work… At what point do we merely turn off and get on with life?

The problem is certainly manifest in Medicine. Most of us invest health –especially our own- with an appropriately significant amount of concern. But it is more of an emotional than intellectual process, and we tend to interpret the concept ‘improbable’ as the much more personal ‘but possible’. Shadows, despite their insubstantiality, hide ‘what-ifs’ –or worse still, unrealistic fears that favourable probability cannot disguise.

Martha was one of those. I would never have guessed it to look at her, though. She sat relaxed and confident in the waiting room, surveying her adopted realm like a tall queen. Crowned with long brown hair, the curls danced from her shoulders as she stooped to pick up a child’s toy, then returned it to him with a smile that would have melted an older stranger. Fifty-ish and surprisingly thin, she was dressed in loose, faded jeans, orange sneakers and a light blue designer tee shirt that said ‘Dare Me, eh?’ She was in control of all she surveyed: monarch of the room.

She stood when she saw me approaching and extended her hand before I was half way across the floor. “I’m so glad to meet you, doctor,” she said loud enough for all to hear, and squeezed my hand like she was doing an exercise in the gym. A full head taller than me, I had to look up to see her face. For a moment, I felt like that little boy whose toy she had rescued, and as I led her back down the corridor to my office I had the distinct impression that, despite her being behind me, nonetheless it was me being taken for a walk like a small dog on a leash.

She sat down on the chair opposite my desk and waited for me to settle into mine before starting the interview. That’s how it felt: she was interviewing me like a reporter hot on a story.

“I’m here,” she said without the usual preliminary pleasantries, “because of a disagreement with my family doctor…” She left her thought unfinished so she could study my face for its reaction, and when she saw nothing but curiosity written on it, continued. “She seemed to feel that my worries about hormone replacement therapies were unfounded.”

She immediately folded her arms across her chest to -as her tee shirt invited me to do- dare her to defend herself. I wondered if she’d chosen it specifically for the visit. I smiled to diffuse her arms, but her body had hardened into place; everything remained on guard, and her eyes perched on her face like a pair of eagles watching me from their aerie in a tree.

I thought I’d keep it simple. Basic. “She felt you needed hormones?” A regal, no-nonsense nod. “And why was that?”

“Hot flushes.”

I duly typed this on my laptop, although I sensed it might be only the tip of a rather unpredictable iceburg. So I waited.

I could sense she was testing me, and the eagles shifted impatiently on their branches. “I don’t need hormones, doctor. I was just going in for my pap smear and she asked me about hot flushes.” A smile passed across her face like a shadow crossing a stage. “I think she just wanted to compare notes with me…”

I tried to concentrate on her mouth, her eyebrows, hair –anything but those unnerving eyes that seemed constantly on the verge of attack. “So you’re not bothered by them?”

She shrugged, but if I hadn’t been staring at her, I might have missed it. I sat back in my chair, wondering where the thread-bare conversation was taking us.

She could see my confusion, although I had tried to hide it behind an Oslerian mask of Aequanamitas. I sometimes find it doesn’t quite cover everything, no matter how I wear it. “Look, she’s a nice woman and I think she was just trying to be kind.” She hooded the eagles and looked over my shoulder at something for a moment. “It was a girl thing, I suspect –you know, an attempt at empathy, wearing my shoes, or something.” One of my eyebrows started to move before I could rein it in and she noticed it and grinned sheepishly. “After I left her office, it dawned on me that she’s probably on hormones herself. An example of the play within the play of Hamlet: The lady doth protest too much, methinks.”

Martha was obviously not your average patient –she even put the ‘methinks’ at the end, where its supposed to be. I was impressed. “You think she was trying to convince herself that hormones were safe?” Might as well cut right to the chase.

She nodded. “I made the mistake of arguing with her and it rolled downhill from there. I shouldn’t have been so righteous, but from my reading, I felt she was mistaken.”

I could tell being a referee in a contest where one party has done extensive research on the subject, and the other was speaking to the contrary out of vested interests would not be easy. Martha had probably read more Shakespeare than me as well. I approached the issue carefully. “What did you find troubling about her opinion?”

She smiled; her trap was laid. “Well,” she started equally carefully, “for a start, the risk of phlebitis is increased by about three hundred per cent on hormone replacement therapy…”

I inclined my head slightly –it was meant to acknowledge the number, but not succumb to it. “Well, in fact the exact incidence of DVT” –I used the acronym for deep vein thrombophlebitis, to show her I had some trifling knowledge of the subject- “is unknown because of the inaccuracy of clinical diagnosis, but if you want to look at another way, its incidence is up to six hundred per cent higher in the first year of use…”

Her smile broadened –she’d been validated. She had been right to worry.

“But,” I added when her smile looked as if it was going to split her face in two, “Six hundred per cent of what?” I let it sink in; I didn’t expect an answer.

“Well, six hundred per cent higher than in non-users…” Her eyes were hunters again –hawks this time, I think. The tone of her voice said that it was obvious. “Six hundred per cent higher, doctor! Six hundred…”

I briefly flirted with some sort of aerial fight, our eyes meeting each other somewhere over the desk in a dominance combat . But I’m not like that. “So, six hundred per cent higher than in non-users in the first year? Otherwise, -what did you quote, three hundred per cent higher?- after the first year of use, I guess you mean?” She nodded impatiently, as if she was being patronized. “And the rate in non-users?”

This time I did expect and answer… Or did I? Three times anything seems like an awful lot more. And six times…? She shrugged as if it were not that important. The relative increase was what mattered. “Well, given that I said that the exact incidence was hard to determine, the figure in many studies has been estimated at around 80 cases…” -I stretched it out for effect- “ 80 cases per 100,000 people. Give or take.” I paused for a moment again. “So, even six times that is –what?- 480 people per one hundred thousand. That’s…uhmm… 0.48 cases per hundred people per year?” It sounded about right… But I have trouble with decimals sometimes.

“Whether I’ve got the numbers exactly right is not the issue, really. The point is more that six times very little, is still very little.”

I could see her mulling it over in her head; doubt lingered on her face, but at least she’d put the hawks away for the day. “An interesting way of looking at it, I have to say… but certainly not intuitive at all, is it?”

I allowed myself a smile that I hoped was non patronizing. “Probability –statistics- is not very intuitive.” Her face stayed neutral. “If I told you I had a way of increasing your chances of winning the lottery by 100% would you be interested?” She nodded, as I knew she would. “It’s simple, really…” She rolled her eyes –no eagles there anymore. “Just buy two tickets.”

She sat back, but I couldn’t tell from her expression whether or not I’d convinced her –or even held her interest. “So tell me, doctor, if I were your sister, would you suggest I go on hormone replacement?”

I sighed; she’d asked for honesty, not medical rhetoric. I locked eyes with her. “If you were my sister?” She nodded –earnestly, I think. “No.”

She seemed surprised after my attempt at explaining probability and risk. “Why not?”

“You’d argue with me every time we met…”

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