麻豆传媒

Flea market

Question: How do fleas so easily find creatures to feed on? I once entered a
house that had been empty for almost a week. It was infested with fleas. Within
seconds, my feet and ankles were covered with the hungry little insects. How did
they know I was there, and that I was a suitable meal?

Answer: The most common fleas are the cat, dog and human fleas,
Ctenocephalides felis, C. canis and Pulex
irritans respectively. Female fleas often lay their eggs on the floor in
crevices or in carpets among dust. Adult fleas can live for up to two years,
during which time the female can lay up to 1200 eggs. Eggs hatch in 2 to 14
days, producing small legless larvae that feed on organic debris.

There are usually three larval stages lasting between 12 and 22 days, but
they can last up to seven months. At the end of this period the larva spins
itself a cocoon in which it forms a pupa after 2 to 3 days. To emerge, the flea
requires external stimulus such as a vibration, the detection of body heat, the
carbon dioxide in a host鈥檚 breath, or an increase in environmental humidity or
temperature. The last two are caused mainly by people switching on heaters when
they return home. If a house is empty the adult fleas stay in their cocoons
until one of those stimuli lets them know that the building is reoccupied.

This explains why people entering a building that has been empty for up to
three years may instantly be set upon by hungry fleas, newly emerged and seeking
their first meal.

Neil Jackson

Medical Entomologist and Parasitologist

Hessle, East Yorkshire

Carrot brains

Question: Why is it that when you repeatedly ask someone addition problems
that all add up to six (such as two plus four, one plus five) for a number of
minutes and then ask them to think of a vegetable, 90 per cent of people will
say 鈥渃arrot鈥�?

The person you are asking must have no knowledge of what you are asking them
or why. The questions should be asked rapidly, encouraging the person answering
to answer them quickly with little thought.

We received over a hundred replies to this question of which we can print
only a small sample here. The reams of data generally confirm the popularity of
鈥渃arrot鈥� but don鈥檛 provide a total explanation.

In summary: 鈥渃arrot鈥� may pop into people鈥檚 minds most frequently because it
is the most common, distinctive vegetable (but not everywhere in the world) and
that frequency may be further boosted by associations between the sounds in the
question and the sounds of the word 鈥渃arrot鈥�. Unfortunately, we don鈥檛 have
really good control data (answers below conflict) to the simple request 鈥淣ame a
vegetable鈥�. More research needed! 鈥擡d

Answer: The same result (90 per cent carrot) may be obtained when the series
of questions is phrased as a multiplication. 鈥淲hat is 2 脳 2 (wait) 脳 2, 脳 2, 脳
2, name a vegetable鈥�. I鈥檝e experimented with this one for several years. Most of
the remaining 10 per cent are people who pause and then name an outrageous
vegetable, or ask a question because they feel pressured.

Extra data: 1. The experiment doesn鈥檛 work well on people who do not have
English as their first language. 2. A curiously common answer is 鈥渙range鈥�, or
鈥渟omething orange鈥�. 3. If you do a similar experiment asking people to name a
vegetable with no preamble, the response is fairly random with peas and potatoes
being the most common.

Favoured hypotheses: 1. 鈥淐arrot鈥� sounds like 鈥渃ount/counting鈥�. 2. The series
of ever increasing numbers resembles a continuously increasing shape鈥攍ike
a carrot鈥攁lthough the 鈥渆quals six鈥� experiment would seem to discount this.
3. The conceptual image of a carrot is the simplest mathematical/geometrical
vegetable: a rotated triangle.

None of these is entirely persuasive and most would predict an occasional
parsnip.

Sean May

Nottingham Arabidopsis Stock Centre, Nottingham University

Answer: Whilst studying psychology at college some years ago, I interviewed
300 students, one at a time, inside a plain, empty white room. I asked them to
answer four simple questions as quickly as they could, regardless of accuracy.
All were in their late teens or early twenties and English-speaking residents of
Britain.

The four questions were: What is 2 plus 1? What is 2 minus 1? What is 2 times
1? Name a vegetable.

The results were: 66 per cent answered 鈥渃arrot鈥�, 20 per cent answered
鈥渃abbage鈥� and the remaining 14 per cent responded with a random selection of
answers (some of which were not vegetables). The similarity of the words
鈥渃arrot鈥� and 鈥渃abbage鈥� (two syllables beginning 鈥渃a鈥�) suggest the explanation
may lie in the system the brain uses to store and retrieve words.

Jean Hamilton

East Grinstead, Sussex

Answer: I have tried the same experiment but instead of sums, I ask the
participant to say 鈥�99鈥� over and over for 60 seconds, then ask the question. The
answer is invariably 鈥渃arrot鈥�. A variant is to ask for the name of a flower, to
which the answer will be 鈥渞ose鈥�, or a number between 1 and 10, to which the
answer is 鈥�7鈥�.

Steve Symonds

Newtown, New South Wales

Answer: I have tried this out on numerous people. Every English person
questioned (around 15) said 鈥渃arrot鈥�. However, every non-English person (six or
so) said something other than carrot. A Japanese person said 鈥渙nion鈥�, two
Italians and an American of Afghan origin said 鈥渁ubergine鈥� (he actually said
鈥渆ggplant鈥�), a South African said 鈥減eas鈥�, and an Indian said 鈥渃abbage鈥�.

Robert Fullerton

London

Answer: I have performed a similar experiment on schoolchildren and
discovered that, at least in South Wales, the preferred vegetable is the humble
potato鈥�18 responded thus, one with 鈥渃abbage鈥� and one with 鈥渃arrot鈥�.

When I asked a different group (who had been performing mental arithmetic
calculations culminating in the number 3), I found 12 chose potato, three chose
carrots, three chose onions and two chose cabbage.

Name and location withheld for fear of ridicule performing a puerile
experiment!

Answer: I asked my wife, a native Dutch speaker, in Maputo, Mozambique, on a
sunny afternoon, several addition problems in English which all added up to six.
Her reply to the question to think of a vegetable was 鈥渨ortel鈥� (Dutch for
carrot).

Fred de Boer

Maputo, Mozambique