diff --git a/books/psicologia/psychology-of-intelligence.mdwn b/books/psicologia/psychology-of-intelligence.mdwn
index ff9bfb1bbaeb16d5ec0afd8edf8aa1f705807c8e..6831b080755960712505e0c8ea1b4c58a4a80f0c 100644
--- a/books/psicologia/psychology-of-intelligence.mdwn
+++ b/books/psicologia/psychology-of-intelligence.mdwn
@@ -4,6 +4,10 @@
 * Publisher: Routledge Classics.
 * Year: 1950. 
 
+## References
+
+* [Piaget's theory of cognitive development - Wikipedia](https://en.wikipedia.org/wiki/Piaget's_theory_of_cognitive_development).
+
 ## Overview
 
 This overview is a mixed of both ideas from the book altogether with other
@@ -33,6 +37,90 @@ not composed of intelligence alone. Other instances exist that might put the
 whole apparatus on restricted modes of operation, such when in a neurosis which
 is a state of constant looping in a given theme.
 
+## Misc
+
+* Perception (imediate contact with the world) (127).
+
+* Habit: beyond short and rapidly automatised connections between per-
+  ceptions and responses (habit) (127).
+
+## Intelligence and equilibrium
+
+    Then, if intelligence is thus conceived as the form of equilibrium towards
+    which all cognitive processes tend, there arises the problem of its relations
+    with perception (Chap. 3), and with habit (Chap. 4).
+
+    -- Preface
+
+    Every response, whether it be an act directed towards the outside world or an
+    act internalized as thought, takes the form of an adaptation or, better, of a
+    re-adaptation. The individual acts only if he experiences a need, i.e., if the
+    equilibrium between the environment and the organism is momentarily upset, and
+    action tends to re-establish the equilibrium, i.e., to re-adapt the organ- ism
+    (Claparède). A response is thus a particular case of inter- action between the
+    external world and the subject, but unlike physiological interactions, which
+    are of a material nature and involve an internal change in the bodies which are
+    present, the responses studied by psychology are of a functional nature and are
+    achieved at greater and greater distances in space (percep- tion, etc.) and in
+    time (memory, etc.) besides following more and more complex paths (reversals,
+    detours, etc.). Behaviour, thus conceived in terms of functional interaction,
+    presupposes two essential and closely interdependent aspects: an affective
+    aspect and a cognitive aspect.
+
+    -- 5
+
+    Furthermore, intelligence itself does not consist of an isolated and sharply
+    differentiated class of cognitive processes. It is not, properly speaking, one
+    form of structuring among others; it is the form of equilibrium towards which
+    all the structures arising out of perception, habit and elementary
+    sensori-motor mechan- isms tend. It must be understood that if intelligence is
+    not a faculty this denial involves a radical functional continuity between the
+    higher forms of thought and the whole mass of lower types of cognitive and
+    motor adaptation; so intelligence can only be the form of equilibrium towards
+    which these tend.
+
+    This does not mean, of course, that a judgment consists of a co- ordination of
+    perceptual structures, or that perceiving means unconscious inference (although
+    both these theories have been held), for functional continuity in no way
+    excludes diversity or even heterogeneity among structures. Every structure is
+    to be thought of as a particular form of equilibrium, more or less stable
+    within its restricted field and losing its stability on reach- ing the limits of
+    the field. But these structures, forming different levels, are to be regarded as
+    succeeding one another according to a law of development, such that each one
+    brings about a more inclusive and stable equilibrium for the processes that
+    emerge from the preceding level. Intelligence is thus only a generic term to
+    indicate the superior forms of organization or equilibrium of cognitive
+    structurings.
+
+    -- 7
+
+    In general, we may thus conclude that there is an essential unity between the
+    sensori-motor processes that engender per- ceptual activity, the formation of
+    habits, and pre-verbal or pre- representative intelligence itself. The latter
+    does not therefore arise as a new power, superimposed all of a sudden on com-
+    pletely prepared previous mechanisms, but is only the expres- sion of these
+    same mechanisms when they go beyond present and immediate contact with the
+    world (perception), as well as beyond short and rapidly automatised connections
+    between per- ceptions and responses (habit), and operate at progressively
+    greater distances and by more complex routes, in the direction of mobility and
+    reversibility. Early intelligence, therefore, is simply the form of mobile
+    equilibrium towards which the mechanisms adapted to perception and habit tend;
+    but the latter attain this only by leaving their respective fields of
+    application.  Moreover, intelligence, from this first sensori-motor stage
+    onwards, has already succeeded in constructing, in the special case of space,
+    the equilibrated structure that we call the group of displacements—in an
+    entirely empirical or practical form, it is true, and of course remaining on
+    the very restricted plane of immediate space. But it goes without saying that
+    this organiza- tion, circumscribed as it is by the limitations of action, still
+    does not constitute a form of thought. On the contrary, the whole development
+    of thought, from the advent of language to the end of childhood, is necessary
+    in order that the completed sensori- motor structures, which may even be
+    co-ordinated in the form of empirical groups, may be extended into genuine
+    operations, which will constitute or reconstruct these groupings and groups at
+    the level of symbolic behaviour and reflective reasoning.
+
+    -- 127-128
+
 ## Logic and psychology
 
     An axiomatics is an exclusively hypothetico-deductive sci-
@@ -171,3 +259,68 @@ Innovation:
     new possibilities.
 
     -- 114
+
+Topology:
+
+    But there now arises a problem whose discussion leads to the study of space.
+    Perceptual constancy is the product of simple regulations and we saw (Chap. 3)
+    that the absence at all ages of absolute constancy and the existence of adult
+    “superconstancy” provide evidence for the regulative rather than operational
+    char- acter of the system. There is, therefore, all the more reason why it
+    should be true of the first two years. Does not the construction of space, on
+    the other hand, lead quite rapidly to a grouping structure and even a group
+    structure in accordance with
+    
+    Poincaré’s famous hypothesis concerning the psychologically primary influence of
+    the “group of displacements?” The genesis of space in sensori-motor
+    intelligence is com- pletely dominated by the progressive organisation of
+    responses, and this in effect leads to a “group” structure. But, contrary to
+    Poincaré’s belief in the a priori nature of the group of dis- placements, this
+    is developed gradually as the ultimate form of equilibrium reached by this
+    motor organisation. Successive co-ordinations (combinativity), reversals
+    (reversibility), detours (associativity) and conservations of position
+    (identity) gradually give rise to the group, which serves as a necessary
+    equilibrium for actions.
+
+    At the first two stages (reflexes and elementary habits), we could not even speak
+    of a space common to the various per- ceptual modalities, since there are as
+    many spaces, all mutually heterogeneous, as there are qualitatively distinct
+    fields (mouth, visual, tactile, etc.). It is only in the course of the third
+    stage that the mutual assimilation of these various spaces becomes system- atic
+    owing to the co-ordination of vision with prehension. Now, step by step with
+    these co-ordinations, we see growing up elementary spatial systems which
+    already presage the form of composition characteristic of the group. Thus, in
+    the case of interrupted circular reaction, the subject returns to the starting-
+    point to begin again; when his eyes are following a moving object that is
+    travelling too fast for continuous vision (falling etc.), the subject
+    occasionally catches up with the object by dis- placements of his own body to
+    correct for those of the external moving object.
+
+    But it is as well to realise that, if we take the point of view of the subject
+    and not merely that of a mathematical observer, the construction of a group
+    structure implies at least two conditions: the concept of an object and the
+    decentralisation of movements by correcting for, and even reversing, their
+    initial egocentricity.  In fact, it is clear that the reversibility
+    characteristic of the group presupposes the concept of an object, and also vice
+    versa, since to retrieve an object is to make it possible for oneself to return
+    (by displacing either the object itself or one’s own body). The object is
+    simply the constant due to the reversible composition of the group.
+    Furthermore, as Poincaré himself has clearly shown, the idea of displacement as
+    such implies the possibility of differentiating between irreversible changes of
+    state and those changes of position that are characterized precisely by their
+    reversibility (or by their possible correction through movements of one’s own
+    body). It is obvious, therefore, that without con- servation of objects there
+    could not be any “group”, since then everything would appear as a “change of
+    state”. The object and the group of displacements are thus indissociable, the
+    one con- stituting the static aspect and the other the dynamic aspect of the
+    same reality. But this is not all: a world with no objects is a universe with
+    no systematic differentiation between subjective and external realities, a world
+    that is consequently “adualistic” (J. M. Baldwin). By this very fact, such a
+    universe would be centred on one’s own actions, the subject being all the more
+    dominated by this egocentric point of view because he remains
+    un-self-conscious. But the group implies just the opposite attitude: a complete
+    decentralisation, such that one’s own body is located as one element among
+    others in a system of displacements enabling one to distinguish between one’s
+    own movements and those of objects.
+
+    -- 123-125