The Unexpected Gift

In one variation of a popular paradox, a friend tells you that she’ll give you a present sometime next week, but that you won’t be able to predict the day on which you’ll receive it.

This is puzzling. If she waits until Saturday, the end of the week, it will be obvious that you must receive the gift on that day, as no other day remains possible. But if we exclude Saturday then the same argument could be used to exclude Friday, and so on back to Sunday. It seems that the friend’s declaration can’t be true — her gift can’t be unexpected.

David Morice offers one possibility that he called “Zeno’s solution”: Your friend, wearing a precision wristwatch, presents the gift in the moment precisely between Friday and Saturday. No reasoning has led you to expect this, so you’re surprised.

(David Morice, “Kickshaws,” Word Ways 27:2 [May 1994], 106-116.) (See the link — Morice offers three other solutions as well, “but I expect that each is logically flawed.”)

The Denomination Effect

In 2009, marketing professors Priya Raghubir and Joydeep Srivastava gave $1 to each of 89 undergraduates and told them they could keep the money or spend it on candy. The students received the money in different denominations — 43 students were given four quarters, and 46 were given a dollar bill. About 63 percent of the students who’d received quarters chose to buy candy, but only 26 percent of those who’d received a dollar bill did so.

In related studies, Raghubir and Srivastava found that subjects who foresaw a need to exert self-control in spending chose to receive money in large denominations. And “[t]ightwads choose to receive money in a large denomination as a precommitment device when the need for self-control is high.”

The lesson seems to be that people are less likely to spend money when they receive it in large denominations. “[L]arge denominations are psychologically less fungible than smaller ones, allowing them to be used as a strategic device to control and regulate spending.”

(Priya Raghubir and Joydeep Srivastava. “The Denomination Effect,” Journal of Consumer Research 36:4 [December 2009], 701-713.)

Changing Times

Egbert de Vries, a Dutch sociologist, has told of how the introduction of matches to an African tribe altered their sexual habits. Members of this community believed it necessary to start a new fire in the fireplace after each act of sexual intercourse. This custom meant that each act of intercourse was something of a public event, since when it was completed someone had to go to a neighboring hut to bring back a burning stick with which to start a fresh fire. Under such conditions, adultery was difficult to conceal, which is conceivably why the custom originated in the first place. The introduction of matches changed all this. It became possible to light a new fire without going to a neighbor’s hut, and thus, in a flash, so to speak, a long-standing tradition was consumed.

“In reporting on de Vries’ finding, Alvin Toffler raises several intriguing questions: Did matches result in a shift in values? Was adultery less or more frowned upon as a result? By facilitating the privacy of sex, did matches alter the valuation placed upon it?”

— Neil Postman, Technopoly, 1992, citing Toffler’s introductory essay “Value Impact Forecaster — A Profession of the Future” in Kurt Baier and Nicholas Rescher’s Values and the Future (1969)

RSS Quiz

The Royal Statistical Society’s Christmas Quiz runs through January 29 this year — 18 fiendish puzzles to mark the tradition’s 30th anniversary.

“Cracking the puzzles below will require a potent mix of general knowledge, logic, lateral thinking and searching skills — but, as usual, no specialist mathematical knowledge is needed.”

Entry is free and open to everyone. The top two entries will receive £100 and £50 in gift vouchers of their choice, and the quizmaster has pledged a donation of £900 to charities nominated by the top performers.

See the quiz web page for rules, entry instructions, and some tips for budding solvers.


In 2011 I published a list of unusual American girls’ names collected by H.L. Mencken in his magisterial study The American Language. I should have gone back for the boys’ names:

  • Allmouth
  • Anvil
  • Arson
  • Centurlius
  • Cho-Wella
  • Clarmond
  • Cluke
  • Comma
  • Crellon
  • Cyclone
  • Doke
  • Elesten
  • Elgne
  • Elvcyd
  • Felmet
  • Florns
  • Habert
  • Harce
  • Human
  • Jat
  • Kark
  • Kleo Murl
  • Koith
  • Lig
  • Loarn
  • Mord
  • Murt
  • Quannah
  • Rephord
  • Terbert
  • Thrantham
  • Torl
  • Valourd
  • Virgle
  • Yick
  • Zelmer
  • Zurr

“In Connecticut, a generation or two ago, there was a politico surnamed Bill whose given-names were Kansas Nebraska. He had brothers named Lecompton Constitution and Emancipation Proclamation, and sisters named Louisiana Purchase and Missouri Compromise.”

(H.L. Mencken, The American Language, Supplement 2, 1948.)

Time’s Up

A perplexing question by the Soviet science writer Yakov Perelman:

If a clock takes three seconds to strike three, how long does it take to strike seven?

Click for Answer


A problem from the October 1962 issue of Eureka, the journal of the Cambridge University Mathematical Society:

Tom is twice as old as Dick was when Tom was half as old as Dick will be when Tom is twice as old as Dick was when Tom was a year younger than Dick is now. Dick is twice as old as Tom was when Dick was half as old as Tom was when Dick was half as old as Tom was two years ago. How old are Dick and Tom?

Click for Answer

“Love Cools Quickly”

Irish proverbs:

  • Laziness is a load.
  • A good run is better than a long stand.
  • The tools are half of the trade.
  • Bribery can split a stone.
  • The pleasant humorous people are all in eternity.
  • A promise is a debt.
  • What cannot be had is just what suits.
  • It is better to be alone than in bad company.
  • It is easier to scatter than to gather.
  • The horses die while the grass is growing.
  • Be afraid and you’ll be safe.
  • The deed will praise itself.
  • Poverty is no shame.
  • It is better to be lucky than wise.
  • Tell me your company and I’ll tell who you are.
  • Time is a good historian.
  • Self-love is blind.
  • Avarice is the foundation of every evil.
  • Patience conquers destiny.
  • Nothing is preferable to reconciliation.

And “There is no forest without as much brushwood as will burn it.”