Logical Reasoning

A logical reasoning test is a type of aptitude test that is widely used by corporate employers to help assess candidates during their recruitment process. Logical reasoning aptitude tests are designed to measure your ability to draw logical conclusions based on statements or arguments, and to identify the strengths and weaknesses of those arguments.

These tests are designed to assess your logical reasoning ability using the information provided. A logical reasoning test is a fundamental part of any assessment. Below follows an overview of the most commonly used logical reasoning tests:

 

Logical Reasoning (additional information)

Today, logical reasoning is the umbrella term for at least three different types of reasoning. These are known as deductive reasoning, inductive reasoning and abductive reasoning and are based on deduction, induction and abduction respectively.

 

 
Logical reasoning tests can thus refer to different kinds of testing, such as aforementioned deductive or inductive reasoning tests. These type of tests can either be verbal or non-verbal and to make it even more confusing, each major test provider SHL, Kenexa, etc using their own terminology and style of testing for logical, non-verbal, abstract, inductive reasoning tests, etc. The schematics above give a clear overview of the relationship of each of the three types of logical reasoning and their relation to the types of tests used and will be explained further below.

 

Deductive Reasoning

In general terms, deductive reasoning means using a given set of facts or data to deduce other facts from by reasoning logically. Deductive reasoning can be used to proof that these new facts are true. For instance the classic example:

 
Major premise: All humans are mortal
Minor premise: Socrates is human
Conclusion: Socrates is mortal

 
Applying the deduction method on the general rule “all humans are mortal” (major premise) in the specific situation “Socrates is human” (minor premise), the conclusion can be drawn that “Socrates is mortal”.

Notice that deductive reasoning provides no new information, it only rearranges information that is already known into a new statements or truths. So deductive reasoning is “if this is true, than this is also true”. Deductive reasoning tests typically contain syllogisms as questions.

 

Inductive Reasoning

Inductive reasoning is looking for a pattern or a trend and then generalizing it. When you generalize and extrapolate the information, you don’t know for sure if this trend will continue, but you assume it will. You therefore don’t know for sure that a conclusion based on inductive reasoning will be 100% true. A famous hypothesis is:

 

‘all swans are white’

 
This conclusion was taken from a large amount of observations without observing any black swan and consequently logically assumes that black swans don’t exist. Inductive reasoning is therefore a risky form of logical reasoning since the conclusion can as easily be incorrect when, looking at the swans example, a black swan is spotted.

Another common example of inductive reasoning used in actual aptitude testing are number sequences. Try to determine the pattern, generalize and extrapolate to find the next number in the series.

 

6, 9, 12, 15, ?

 
The logical answer to this trend seems 18, but you can’t ever be 100% sure, maybe the number represent days or hours or something weird that you don’t expect and which causes extrapolating to give different results.

Perhaps the most common form of inductive reasoning tests consist of non-verbal figure sequences and are also known as abstract reasoning tests. They follow the same methodology as mention earlier, find the pattern, and extrapolate to find the next figure.

 

 
That is what inductive reasoning is all about, looking at the given data, making a generalization, and extrapolate the pattern. In all the above examples, there is a sense of a generalized judgment, which may or may not turn out to be true. Whereas in deductive reasoning, there is no judgment. The conclusions are mostly true, based on the given situation.

 

Abductive Reasoning

Abductive reasoning is the third form of logical reasoning and is somewhat similar to inductive reasoning. It was first introduced by the term “guessing”, since conclusions drawn here are based on probabilities. In abductive reasoning it is presumed that the most plausible conclusion is also the correct one. Example:

 
Major premise: The jar is filled with yellow marbles
Minor premise: Bob has a yellow marble in his hand
Conclusion: The yellow marble in Bob’s hand was taken out of the jar

 
By abductive reasoning, the possibility that Bob took the yellow marble from the jar is reasonable, however it is purely based on the speculation. The yellow marble could have been given to Bob by anyone, or Bob could have bought a yellow marble at a store. Therefore, abducing that Bob took the yellow marble, from the observation of “the yellow marble filled jar” can lead to a false conclusion. Unlike deductive and inductive reasoning, abductive reasoning is not commonly used for psychometric testing.

 
 

Formal and Informal Logic Reasoning

Next to these 3 types of logical reasoning it is also possible to make a difference between formal reasoning and informal reasoning. Formal reasoning is a type of logical reasoning based on valid premises and therefore valid conclusions, thus it is a form of deductive reasoning. It provides no new information, but only rearranges known information to a new conclusion.

Next to formal reasoning we also have informal reasoning. This form of logical reasoning possesses all the elements of formal reasoning, like the deduction part, however it also includes probabilities and truths about premises and conclusions. It can be said that informal reasoning is related to abductive reasoning, one of the other three types of logical reasoning explained above

Combining these two forms of logical reasoning together with the three different types results in the following distinguish in logical reasoning:

1. Deductive
   1. Formal deductive reasoning
   2. Informal deductive reasoning
2. Inductive
   1. Formal inductive reasoning
   2. Informal inductive reasoning
3. Abductive
   1. Formal abductive reasoning
   2. Informal abductive reasoning

Wrong can be Right Logically

Within logical reasoning it can sometimes happen that the premises and conclusion seem obviously wrong, but are logically speaking correct when applying one of the logical reasoning types mentioned above. Be aware that conclusions are drawn based on logical reasoning and not on the validity of the context of certain premises or conclusions. Example:

 
Major premise: Eating a lot makes you lose weight
Minor premise: Craig is obese
 
Question: What can we do to make Craig lose weight?
Conclusion: Make Craig eat a lot

 
By just observing the context of the words you would think that this conclusion is incorrect, since you know form everyday life that eating a lot does not make you lose weight at all. On the contrary it makes you gain weight. However based on logical reasoning this conclusion is most certainly correct, since both premises are valid, which automatically makes the conclusion a valid conclusion.

What you need to understand is that the correct answer to any given logical reasoning argument requires the proper identification of relationships between assertions (typically facts and opinions) and not the accuracy of those assertions.