Mental Organs

Phrenology was an important part of popular culture in Victorian England and in Europe during the 19th century.

Four assumptions behind phrenology

Gall assumed that minds were made up of different mental “organs”, each of which is localized in distinct parts of the brain.These include not only basic domains like language and colour but also self-esteem and secretiveness which is distinct from cautiousness. Assumption 1

A further assumption Gall made is that the mental faculties he listed were innate propensities or predispositions to behave or perceive the world in a particular way. Assumption 2

Gall also assumed that each faculty is determined by the content of the information on which it relies, not by the way this information is used to carry out different tasks. We talk about modes of operation to refer to the various ways in which knowledge can be recruited for different kinds of tasks. Assumption 3

Modes of operation? Refers to the various ways in which knowledge can be recruited for different kinds of tasks Memory Reaso n Classif y Atten d Modes of Operation

Gall’s mental faculties were considered by him to be domain- specific, not general modes of operation. According to Gall’s taxonomy, there are no mental organs localizable in the brain that are responsible for general abilities like reason, attention or memory.

Finally, Gall assumed that an especially well developed faculty (i.e. mental organ) requires a correspondingly well developed cortical (i.e. physical) organ. Because the bones of an infant are soft and pliable, a highly developed cortical organ will create a protrusion of the adjoining skull that is measurable. Assumption 4

What does this view imply about constructs like general intelligence, reason, memory and imagination? Gall:There are no such mental organs (faculties)!

So, it is possible on this view to be very gifted in some particular domain of knowledge and yet be congenitally predisposed (predisposed at birth) to be well below average ability in other faculties.

It should be clear that Gall was interested in measuring differences in the talents or natural propensities between individuals. So his approach, for better or worse, required him to look for exceptional cases whom he considered either very gifted or seriously deficient in a particular faculty.

Domain-specific abilities (for examples, see the accompanying figure) are referred to as vertical faculties. The function of a vertical faculty is to provide us with a particular kind of knowledge about the world (that’s why we say a vertical faculty is domain-specific).

Some examples of cross-modal perceptual representations that we investigate still exist in psychology. For example, this object directs your visual attention to the right side of space, but also movements will occur faster in this direction, as will your response to sound when occurring on your right as opposed to your left. Our representation of space integrates a number of modalities.

For Gall, there is no specific mental organ for memory, nor for any of the Aristotelian faculties. Rather, each separate biological cortical organ has its own special memory. Similarly, there was no organ for the ‘Intellect’. In other words, Intellect could not be neurologically localized and so was not a biologically plausible category. Instead, each mental organ had its own intelligent mode of functioning.

The goal of modern psychology is to understand the details of mental computations in a particular domain, so we need to go well beyond Gall’s notion of mental organs.

The term we now use, modularity, refers to the idea that complex neural systems responsible for some task (e.g. understanding a sentence) are organized into subcomponents -- modules -- which are functionally independent of one another. This principle of modularity makes very good sense when processing tasks are very complicated (like sentence comprehension). In non-modular systems, a small change to improve one part (whether by natural selection in the case of the brain or by a human designer in the case of a machine) would have consequences (often undesirable) in many other places.

Dissociation Methodology Modular System A Modular System B

HOW CAN WE IDENTIFY THE ACTUAL MODULES OF MIND? Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRIN TGrapheme- phoneme conversion rules Semantic System

Letter Identification Orthographic Lexicon Phonological Lexicon SPEECH OUTPUT PRIN TGrapheme- phoneme conversion rules Semantic System BOOK LEOPAR D PINT HAND FOR READING A DANGEROUS FELINE PREDATOR A MEASURE OF VOLUME FOR LIQUID BODY PART OOK IS PRONOUNCED ‘UK’ B IS PRONOUNCED ‘BUH’ B-O-O-K IS ‘BOOK’ LEXIC AL NONLEXICAL VOO K

TASK 1: READ ALOUD YINT, GOOP, SIFE, LUNK ETC. TASK 2: READ ALOUD PINT, ACHE, BEAD, BOTH, ETC. PHONOLOGICAL DYSLEXIA IMPAIRMENT TO NONLEXICAL ROUTE SURFACE DYSLEXIA IMPAIRMENT TO LEXICAL ROUTE OKA Y WE ALWAYS MEASURE IMPAIRMENT RELATIVE TO A GROUP OF NORMAL CONTROLS

Surface Dyslexic Phonological Dyslexic Normal Control Accurac y 100% 50% Exception words Pronounceable Nonsense words A classic double dissociation

Surface Dyslexic Phonological Dyslexic Normal Control Accurac y 100% 50% Exception words Pronounceable Nonsense words This is not a classic double dissociation Why not?

Surface Dyslexic Phonological Dyslexic Normal Control Accurac y 100% 50% Exception words Pronounceable Nonsense words This is not a classic double dissociation Why not? Patient A is better than Patient B on Task X. Patient B is better than Patient A on Task Y.

PHONOLOGICAL AND SURFACE DYSLEXIA TOGETHER MAKE UP A DOUBLE DISSOCIATION BETWEEN THE LEXICAL AND NON-LEXICAL READING ROUTE. THE EXISTENCE OF THESE TWO READING DISORDERS PROVIDES EVIDENCE THAT THESE TWO ROUTES FROM PRINT TO SOUND ARE SEPARATE FUNCTIONAL COMPONENTS (MODULES) OF THE READING SYSTEM. ANOTHER WAY TO STATE THIS IS THAT THE LEXICAL AND NON-LEXICAL READING ROUTES ARE DOUBLY DISSOCIABLE.