This is Peacocke’s own position.

301
6. This is Peacocke’s own position. I have criticised it in Bermu´ dez 1994, and he
replies in Peacocke 1994.
7. I shall return to this in the final section of this chapter.
8. This is stressed in Peacocke 1992.
9. This is certainly Spelke’s own view: “The earliest developing conceptions of
physical objects are the most central conceptions guiding mature object perception
and physical reasoning. For adults, such conceptions are overlaid by a wealth
of knowledge about the appearances and the behavior of particular kinds of objects.
Even this more specific and limited knowledge, however, reflects the core
knowledge from which it grew” (Spelke and Van de Walle 1993, 157).
10. It is worth mentioning in this context that, although developmental psychologists
seem to find unproblematic the conclusion that infants show surprise in the
drawbridge experiments because it is impossible for the screen to pass through
the object, this is at best questionable. On the inferential interpretation, the surprise
would be due to the infant’s identifying an object and inferring from their
knowledge of how objects behave that what they see is impossible. But why say
this rather than that the infants show surprise simply because there are no precedents
for what they see? Certainly, more argument is needed than simply pointing
out that what the infants see is really impossible.
11. I am grateful to Jim Russell for pressing me here.
12. Some qualifications are required here. It is known from studies of adult subjects,
for example, that perceptual predictions of object transformations and interactions
tend to be based on kinematic, rather than dynamic, principles and
information (Cooper and Munger 1993). This has obvious computational advantages
and clearly shows that ordinary object perception need not always involve
the perceptual pick-up of the full range of object properties. But that is no objection
to the claim that perception of objects depends on perceptual sensitivity to
object properties. Perceptual sensitivity to object properties needs to be understood
at the level of competence rather than performance.
13. The experiments on infant expectations in collision events reported in Baillargeon
1995 are an excellent example of how detailed work might be carried out
on infant sensitivity to object properties.
14. This would be consistent with the general view of the importance of agency
in mental development outlined in Russell 1996, and is of course a modern version
of a broadly Piagetian position.
15. The inference to an apelike (pongid) neural organization is based on the location
of the lunate sulcus, on the assumption that the massively expanded posterior
parietal cortex characteristic of the human brain pushed the lunate sulcus backwards
and downwards to the position it occupies in the human brain.
16. It has occasionally been suggested in the literature that Neanderthal hominids
had a completely modern superlaryngeal vocal tract. Liebermann (1991)
compellingly argues that this would have meant that Neanderthal’s larynx was in
his chest.
302 Notes to Pages 61–78
17. The crucial claim is, of course, that the emergence of language did not significantly
precede the descent of the larynx. This presupposes an equation of language
with speech. Some authors have objected to this, suggesting that a gestural
language might have preceded spoken language (Corballis 1991), or that Homo
erectus had a protolanguage comparable to that of a 2-year-old child (Parker and
Gibson 1979). Both these suggestions remain at the level of conjecture, however.
18. Farah (1990) distinguishes between two types of simultagnosia, which she
terms dorsal and ventral (after the location of the relevant lesion site). Although
ventral simultagnosics cannot recognize multiple objects, they can nonetheless see
multiple objects (unlike dorsal simultagnosics).
19. Farah (1990) questions whether patients with associative object agnosias really
do have intact visual perception, noting that they often fail more sophisticated
visual tests. Nonetheless, they generally seem to have relatively unimpaired visual
perception in comparison with apperceptive agnosics, which seems enough to
suggest a significant distinction between the two groups of disorders.
20. See Shallice 1988, section 8.4, for an illuminating discussion of the connections
between Marr’s theory and relevant neuropsychological findings.
21. This is not to deny that the 3D sketch is itself a content-bearing state. See
Bermu´ dez 1995e for further discussion.
Chapter 4
1. The minimal account is an account of what it is in general for a state to have
content. This is a different level of theorizing from specific theories of content. A
possible-worlds account of content is an example of such a specific theory, as is
Peacocke’s own theory of scenario content. The general theory explains what the
specific theories have in common.
2. The importance of an exceptionless connection for the theory of information
is stressed in Dretske 1981, chap. 3. He gives several arguments for refusing to
accept conditional probabilities of less than 1. The most important are the following.
First, doing otherwise would admit the possibility that a signal could carry
the information that s is G and the information that s is F, but not the information
that s is G and F (because the probability of s being F and G might be below the
acceptable value of conditional probability). Second, the flow of information is
transitive and that this transitivity would be lost if the value of conditional probability
were less than one.
3. It is this that led Dretske substantially to modify the theory proposed in Dretske
1981. See Dretske 1990 and chapter 3 of Dretske 1992.
4. This is central to J. J. Gibson’s notion of the direct perception of affordances,
which will be discussed in the next chapter.
5. Although the number of approaches to the magazines for rats in the omission
schedule eventually fell below the level for the control group, for which the
Notes to Pages 78–88 303
instrumental contingency was maintained, it remained significantly higher than
the level for a second control group, for which food and tone were unpaired.
6. This is noted in Peacocke 1983, 61.
7. In fact, this is precisely the form that Bennett adopts for the teleological laws
that he thinks explain much animal behavior. The form of a teleological law for
Bennett is this:
(x)(F )(t)((Rx & x registers that F/Gx at time t) ® Fx at time t 1 d)
Rx is to be read as the claim that suitable enabling conditions are satisfied (including
the animal’s having the satisfaction of G as a goal); F/Gx as the claim that x
is so structured that the truth of Fx at a later time (t 1 d) is causally sufficient for
Gx at a still later time.
8. The core of Smolensky’s proposal is that compositional structure can be captured
within a network if the network represents particular “fillers” (e.g., a noun)
occupying particular roles (e.g., the role of a grammatical object). But there are
other ways in which PDP researchers have suggested that the compositionality
requirement might be satisfied without collapsing into CTC. Ramsey (1992), for
example, describes a class of connectionist networks in which the different syntactic
roles of particular atomic units are encoded via slightly different patterns
of activation. These different patterns of activation legitimate different types of
molecular combination.
Chapter 5
1. Although Gibson himself displayed little interest in the matter, there are important
processing questions about the relation between retinal flow and flow in the
optic array. See Harris, Freeman, and Willis 1992 for a framework within which
these questions might be addressed.
2. An interesting illustration of the explanatory powers of the theory of invariants
comes with the traditional problem of size constancy. Depending on one’s
distance from an object, the solid visual angle that it subtends will vary. So why
does the object not seem smaller or larger, depending on one’s distance from it?
There is a perceptual invariant that might well explain why objects are perceived
as being of a constant size, irrespective of their distance from the perceiver. The
relevant invariant is the ratio of an object’s height to the distance between its base
and the horizon. This ratio remains constant irrespective of the object’s distance
from the perceiver.
3. This is, of course, one of the ways in which Gibson himself describes it.
4. The efference copy is a perception of the motor command as it leaves the motor
apparatus. The efference copy is usually distinguished from what is known as
the corollary discharge (Gallistel 1980, chap. 7). ‘Efference copy’ and ‘corollary
discharge’ both refer to the same signal, but there are two different theories about
the role that the signal plays in controlling action, and in particular in allowing