Do Schizophrenia Patients Really Have Impaired Logic?

Unsplash/Roberto Sorin

It’s notoriously one of the first observations that researchers tend to think of when discussing patients with schizophrenia. Aside from the obvious presence of hallucinations and delusions, people with schizophrenia have problems with logic.

What exactly is meant by “logic”? This is where it gets murky.

Leading research in the field of neuroscience and psychology that is awarded hundreds of thousands if not millions of dollars backed by well-established organizations in the field generally support this notion that patients with schizophrenia exhibit poor reasoning capabilities, which can be used interchangeably in the field with the word, “logic.”

Perhaps that is a misnomer. As a result of this conflation, treatment options within these organizations and scientists veer towards developing more medications that treat allegedly faulty neurocognitive deficits instead of cognitive training programs that might rehabilitate lost cognitive capacities, which have yet to be further broken down into prime, distinct processes. But patients often complain about the faults of medications which can lead to poor side effects and often want to see more innovation in non-drug clinical interventions.

Few researchers have taken a stance against the definitions of reasoning and logic. But for those that have spoken against it, their research interests bear some potentially revealing observations about what it means to have “schizophrenia.”

A paper published in 2000 in the Harvard Review of Psychiatry called out the research industry’s imperfect definitions of “logic” when conducting research into schizophrenia patients. According to the authors, who have real work experience in psychiatry, the term “logic” up to the date of this paper’s proposal (which was 1999) was poorly defined and lacked distinction between groups of participants.

As a result, patients with schizophrenia were typically clumped together, making a rather heterogenous sample. That is a sample where patients with schizophrenia typically appear to have relatively little in common between one person and the next in the ways they exhibit symptoms.

When conducting studies on “logic” or “reasoning capacities,” the authors argued that many researchers fail to distinguish between the types of reasoning. So, the authors made a point to define what types of reasoning they would test for. More recent papers published in Psychopathology (2015) and Schizophrenia Research (2011) reiterate the need for this distinction.

Their definitions are as follows:

Premise: The “input” from which later conclusions are drawn. Premises can include sensory information as well as information from hallucinations. Premises might be true or false.

Conclusion: The “output” that “follows the premises. It can be true or false.

Logical inference: The process that a person can move from premises to conclusions, which can take the form of deductive or inductive reasoning.

Syllogistic logic: A form of deductive logic that makes reference to part-to-whole relationships defined by common attributes (ex: if all ravens are black, then necessarily some ravens are black, although it might not be true that if some ravens are black, then necessarily all ravens are black)

Propositional logic: AKA “conditional logic,” makes reference to a class of relationships that are vaguely conditional in nature.

Type A hypothesis: Refers to one of the two ways a false conclusion can be reached, and the choice of premises is inadequate.

Type B hypothesis: Refers to the second of two ways in which a false conclusion can be reached: the inferences used are invalid.

Taken with these definitions, scientists then designed new studies that would distinguish between groups of varying schizophrenia symptom presence.

In a study designed to decipher the exact distinctive qualities that result in impaired reasoning strategies, 21 patients with schizophrenia and 21 patients with disorders other than schizophrenia were asked to perform a logic test that tested their abilities to form abstract thinking. Patients with schizophrenia performed just as well as the controls in all measures except for the syllogistic logic, where they performed more poorly.

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The same researchers made a distinction between the type of patients with schizophrenia they used. They specifically used delusional patients diagnosed with schizophrenia, non-delusional patients with schizophrenia, and controls without schizophrenia. Doing so allowed the researchers to determine if there was a difference in the group’s “inference” making skills. That is, were the false conclusions arrived at due to false premises (delusions) or otherwise?

In logic models, false conclusions can arise from both faulty reasoning processes but also faulty premise-gathering processes. Sound familiar? Faulty premises can arise from symptoms such as delusions and hallucinations, which are not experienced by “healthy” controls. Thus, these faulty premises can contribute to a misguidance of information, which could lead individuals to arrive at different conclusions than their “healthy” controls.

Modern Research: Where Are We Now?

Despite being introduced to a reputable journal, this paper has only been cited 59 times. Instead, a recent paper published in 2004 and cited 1573 times continued to use a broader definition of “reasoning and problem solving” capacities.

The “reasoning and problem solving” cognitive strategies were measured by the Wisconsin Card Sorting Task, Matrix Reasoning tasks, and Block Design, among others. While they may be robust measures to assess cognitive reasoning strategies, these measures do not necessarily distinguish between different types of “logic” in the linguistic sense, including syllogistic logic. Furthermore, while the authors note that “these high-level cognitive practices often demand relatively intact lower-level processes,” the “lower-level processes” are the point of discussion in the 2000 article. Combining measures of both lower-level processes with high-level cognitive processes would conflate the processes, which would affect results. Lower-level processing (premise gathering) problems might affect one’s ability to reason.

Remaining Questions

Can certain patients with schizophrenia be rehabilitated with vocational education concerning their syllogistic reasoning capabilities? Currently, there is minimal effort on the part of researchers to examine this.

Perhaps this is impossible, as leading researchers tend to think. Perhaps the author of this post is truly “Living as an Outlier” by exercising any deductive reasoning quality in tangent with the diagnosis of schizoaffective disorder. Or maybe, somebody has got something wrong about what it means to be “psychotic.”