Neuropsychology

Memory Systems Detective

Three fictional profiles across six memory measures, and three claims about separable systems. For each claim on each profile there are three honest answers, and one of them is used more than the others.

Simulated — invented people, invented measures, invented control groups

Learning objective

By the end you should be able to say what a profile must contain before it supports a dissociation between memory systems.

About 15 minutes. Nothing you do here is saved or sent anywhere.

Nobody here is a patient

Invented profiles with invented numbers, written to make particular inferences possible or impossible. No real person, published case or clinical instrument is described, no syndrome is named, and nothing here diagnoses, assesses or gives a prognosis for anybody. Memory difficulty is described in terms of tasks, never as a description of a person.

Read the profile - all six measures, against their own controls.
Judge the claim in the banner: does this profile support it, count against it, or fail to decide it?
Three claims, three profiles, then read the grid.

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The profiles are drawn and the claims marked in your browser, so they cannot run with JavaScript switched off. The rest of this page is readable without it.

What does that pattern establish about memory? That short-term and long-term memory are separate systems That the two tasks do not depend on all the same things - which is less than "separate systems" and is what the evidence gives Only that recalling a list after thirty minutes is harder Nothing until you know what the control group did on each task

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Key terms

Control group: The comparison sample for one measure. Each measure here has its own, which is why a profile is read measure by measure rather than as a single score.
Episodic and semantic memory: Memory for particular experienced events, and memory for facts not tied to the occasion on which they were learned.
Recall and recognition: Producing the material yourself, and picking it out from alternatives. They make different demands, so a gap between them has more than one reading.
Dissociation: A pattern in which one measure is impaired and another is not. What it supports depends on what else the profile contains.

How far this profile sits from its control groups

The six measures

Each measure, what it asks the person to do, and how far this profile sits from its control group
Measure	What it asks for	Distance from controls	Standing

Background

Your grid so far

A different person recalls nothing after thirty minutes and recognises normally. You want to know whether the difficulty is at retrieval or at storage.

Which addition would come closest to deciding it? Give the recall test again after a longer delay Make the recognition test hard enough that healthy controls score the same on it as they do on recall Test recall with more words Scan the person and see which structures are damaged

"Cannot decide" is a real answer, not a hedge

A third of the grid cannot be settled by the profile in front of you. Profile A settles all three claims and is the only one that does; that is what makes it a textbook case rather than a typical one. A profile decides a distinction only when one measure is clearly below its controls while another, comparable one is clearly not - and "comparable" is doing a great deal of work in that sentence.

Separable is a weaker claim than separate

Evidence that two tasks come apart shows that they do not depend on all the same things. It does not show that there are two systems, that each has a location, or that either is a natural kind. The multiple-systems account of memory is a good theory supported by convergent evidence from many sources; no single profile establishes it, and the wording is worth keeping honest.

Recall against recognition does not settle retrieval

The pattern in profile C - recall at floor, recognition normal - is the one always cited for a difficulty at retrieval rather than at storage. It does not establish it, because recognition is the easier task: a memory trace too weak to be produced from nothing can still be strong enough to be picked out of two options. The two tasks would have to be matched for difficulty in healthy people before the comparison meant what it appears to mean, and matching them is genuinely hard.

Every measure is impure, and some are impure together

Profile D is impaired on every verbal measure, including word knowledge. Its episodic scores are therefore not readings of episodic memory: they are readings of episodic memory for material the person no longer knows well. And the one intact measure - skill learning - differs from the impaired ones in system and in material and response, so even that contrast cannot be pinned on the distinction it appears to show.

A low score has several explanations before "damage"

Profile E is mildly below controls on everything and selectively below on nothing. Reduced effort, fatigue, poor sleep, pain, medication, low mood, anxiety about being tested, a language other than the one being tested in, uncorrected hearing, and simply having a lower starting point than the control group all produce that shape. So does a genuine general slowing. Nothing in the profile chooses between them, and reaching for a memory system is the least well-supported move available.

A behavioural profile is not a map

None of this page mentions anatomy, on purpose. The distinctions these profiles bear on are between what tasks require, not between structures. Structures matter, and the mapping between a profile and a structure is many-to-many. The same profile follows damage in several places, and damage in one place produces several profiles depending on extent, connections and what else went with it.

What this does not demonstrate

No syndrome is named. Several profiles resemble textbook descriptions. Naming them would encourage reading a profile as a label rather than as evidence.
The intended answers are judgements. Reasonable people would argue about several cells.
Six measures is very few. Real batteries use many more, and would separate several things this tool merges - recall of stories from recall of word lists, recognition of faces from recognition of words, familiarity from recollection.
No anatomy, and no prognosis. Nothing here says where anything is or what will happen to anybody.
Control-referenced scores are not diagnoses. A score below a control average is a position in a distribution. It becomes a clinical statement only with a great deal of context that no number on this page contains.