New Scientist - USA (2020-08-29)

29 August 2020 | New Scientist | 19

PEOPLE given instructions on

how to succeed at a widely used

type of IQ test end up with far

higher scores than those who take

the test without learning these

tips beforehand – throwing into

question the validity of these

kinds of tests and contributing

to critiques of IQ tests in general.

That is the main finding of a

study on “progressive matrices”, a

kind of IQ test that displays a series

of changing shapes. The test-taker

has to figure out which shape

would logically come next.

The most popular version,

Raven’s Progressive Matrices,

has been around since the 1930s.

In the current study, Benedikt

Schneider at Saarland University

in Saarbrücken, Germany, and his

colleagues used a competing test

called the DESIGMA-Advanced.

The team asked 341 students

to complete the test. About half

of them were randomly assigned

to watch a video on information

unrelated to the test. The other

half watched a 13-minute video

that explained the “rules” behind

the test. Although matrices tests

vary in design, most are based on

the same five or six basic rules:

for example, an element might

rotate clockwise or anticlockwise

from one picture to the next.

The group that watched the

unrelated video got an average

of nine correct answers on a test

consisting of 28 questions. The

tutorial group averaged 18 correct

answers. That difference equates

to about 18 extra IQ points, though

a typical IQ test uses more than

just progressive matrices

(Intelligence, doi.org/d629).

The researchers are quick to

point out that nobody’s actual

intelligence level increased; only

their test scores rose. But what

does that mean for these tests

going forward? If subjects can

increase their scores by simply

watching a short video – and there

are many such YouTube videos

that have millions of views – how

can the tests still be valid?

“This might mean curtains for

tests like Raven’s,” says Stuart

Ritchie at King’s College London.

“It’s basically as if someone

posted up all the vocabulary

test words online so people could

look them up in the dictionary

just before they do an IQ test.

It makes the gains hollow.”

Though Schneider’s team didn’t

investigate Raven’s Progressive

Matrices, a 2015 study found that a

brief video tutorial also increased

gains on that test, albeit less than

in the current study. Pearson, the

publisher of Raven’s tests, didn’t

respond to requests for comment.

The risk of video tutorials

compromising the validity of

some tests “is indeed possible”,

says Schneider. Two of the paper’s

co-authors designed the DESIGMA

test that was analysed, so they are

quite aware that their research

might undermine the test.

One way to get around this, says

Schneider, would be to have all

test-takers watch a video of the

rules, or even to incorporate such a

tutorial into the test itself.

Ritchie thinks this should

already be the norm. “This is what

a good intelligence tester should

be doing when they give the

instructions for the test,” he says. ❚

“The catfish may be using

a form of aerial tasting

thanks to the taste buds

that blanket their bodies”

RA

WF

8 /A

LA

MY

Animal behaviour

Walking catfish are

the first fish known

to ‘smell’ on land

WALKING catfish are sometimes

literally fish out of water, but they

function quite well as a landlubber –

and they are now the first fish

confirmed to “smell” through air.

Native to South-East Asia,

walking catfish (Clarias batrachus)

aren’t content to glide through one

body of water their whole lives.

They can travel to a new pool by

leaving the water and “walking” on

their fins over land, breathing the air.

Similar amphibious fish were

assumed to use their vision to

navigate on land, says Noah

Bressman at Chapman University

in California. But walking catfish

commonly come ashore at night,

and have tiny, underdeveloped eyes.

Curious to find out if the fish

were sensing chemicals in the air,

Bressman and his team caught 150

walking catfish and placed each

in an enclosure on land to expose

them to a battery of odoriferous

substances. The fish flopped away

from noxious hydrogen sulphide,

but chased down the scent of pond

water and alanine – a compound

that induces a strong taste response

in submerged catfish (Journal of

Fish Biology, doi.org/d63j).

The findings suggest that walking

catfish are the first fish known to

use “chemoreception” out of water,

and Bressman says they may use

this sense to orient themselves on

land. Fish weren’t thought capable

of this because their olfactory and

taste systems evolved in water.

“Underwater, taste and smell

go hand in hand,” says Bressman.

Unlike humans, who taste with

direct contact but can smell from

afar, fish “can both taste and smell

compounds that are originating

from a long distance because of

the liquid environment”, he says.

Bressman says the catfish may

be using a form of aerial tasting

thanks to the taste buds that

blanket their entire body, even

their sensitive whiskers.

Walking catfish are invasive in the

south-east US. Knowing how they

make their pond-hopping decisions

could help stop their spread. ❚

Jake Buehler

Human intelligence

Douglas Heingartner

Defeating the IQ test

Simple tutorials boost scores, undermining the validity of IQ tests

You can boost your

IQ score by watching

an explainer video