Philosophy, Psychology and Neuroscience Research Seminar*
Venue: Psychology Seminar Room 511, 58 Hillhead Street, Glasgow G12 8QB (unless otherwise noted)
Seminars are followed by cheese and wine, plus dinner and drinks with the speaker and respondent for those who wish to attend. All welcome!
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Frank Durgin (Psychology, Swarthmore)
‘The angular expansion hypothesis of locomotor space perception’
The conscious perception of locomotor space (or action space) seems to be greatly distorted (ground distances appear much shorter than they are; hills look much steeper than they are, etc.) yet perception provides the basis for excellent control of action. Could large and systematic distortions in perceived locomotor space be for the purpose of action control? As a rough analogy, note that perceptual sensitivity trumps perceptual accuracy in the control of action – or watchmakers wouldn’t use magnifying glasses. I will review a large body of evidence suggesting that many well-documented and systematic biases in the perception of locomotor space arise from an angular coding scheme that may provide more efficient motor specification and/or feedback sensitivity for the control of action. Two interesting characteristics of the theory are that (1) its development is based on parameter measurement rather than null-hypothesis testing, and (2) much of the data used in support of the theory was collected or replicated by other labs before the theory was proposed. The critical new empirical observation of the theory is that while angular variables, like egocentric direction, are fundamental to action control, they are grossly and systematically distorted in spatial perception. This observation is sufficient to explain a great deal of historical data. The critical new theoretical observation is that stable distortions of this sort may be quite useful for action.
‘What is “embodied perception” the embodiment of? A critical review’
The use of the scientific method in the study of conscious perceptual experience is intended to prevent it from becoming a tumbling ground for whimsy. Taking perceptual experience seriously can be a very productive scientific enterprise, but the distinction between measurable perceptual bias and experimental artifact or publication bias has often been strikingly hard to pin down. Here I will review some of the empirical observations that have led a number of researchers to question the merits of whole classes of claims that have been splashing across the pages of prominent journals. Based on my own work, I will emphasize the explanatory advantages of the participant compliance (or demand characteristic) account of several otherwise strange and surprising findings that are ostensibly perceptual. But I will also place this type of basic psychological explanation of these kinds of findings within a broader theoretical context of systematic confirmation bias in psychological science. That is, ongoing crises concerning statistical hypothesis testing in psychology, the concomitant crisis concerning replication, and the ever-present risk of scientific “truthiness” encouraged by a rational cost-benefit analysis of selection bias in journals ought all be relevant factors in the evaluation of the recent flood of claims regarding the strangely metaphorical embodiment of perception.
Robert Audi (Philosophy, Notre Dame)
‘Normativity and Generality in Ethics and Aesthetics’
Moral properties such as being wrong or being obligatory are not brute but based on other kinds of properties, such as being a lie or being promised. Aesthetic properties such as being graceful or being beautiful are similar to moral properties in being based on other kinds of properties, but in the aesthetic cases it may be impossible to specify just what these grounding properties are. Does any single property ground poetic beauty in the way promising grounds obligation to do the promised deed? If aesthetic properties do differ from moral properties in this way, may we conclude that, although ethics is like aesthetics in being a realm of intuitive and perceptual knowledge—or at least intuitive and perceptual sensitivity—it is unlike aesthetics because the latter lacks principles that connect grounding properties with aesthetic properties? Are there any such generalities in aesthetics, or even aesthetic generalities connecting aesthetic properties with other aesthetic properties? If there are, how much like or unlike rules and principles in ethics are they? This paper explores all these questions in the light of examples from the arts, with poetry as the main case study.
Colin Blakemore (School of Advanced Study, University of London)
What has science ever done for perception?
Sensory physiology and psychology have made important contributions to our understanding of perception, but there remain deep unsolved questions. I shall start with two assumptions: 1) the high metabolic cost of impulses puts value on elimination of redundancy and on sparse coding; 2) genetic mechanisms and experience-dependent plasticity contribute to the creation of stimulus selectivity in sensory neurons. These principles are essential the same as two of the dogmas of Barlow’s (1972) classic neuron doctrine for perceptual psychology. However, I shall question two other dogmas of Barlow—that impulse rate indicates only the certainty that the preferred feature is present; and that the content of perception is not dependent on combinatorial rules of usage of nerve cells.
The encoding properties of low-level sensory neurons are always are essentially ambiguous, in the sense that variation of the stimulus along many dimensions leads to variation in the probability of impulses. Hence there is no feature whose presence could be unambiguously signalled by impulses in such a neuron. It follows that disambiguation involves comparison of signals in several neurons, either explicitly, through convergence on to a shared target neuron, of by some other mechanism for comparing the activity of different neurons. I shall argue that one of the functions of non-primary sensory areas in the cortex of higher mammals is to make explicit the spatial and temporal relationships between the activity of separate neurons in the primary area. An interesting question is whether all the discriminable aspects of a sensory experience correspond to such explicit encoding.
Sensory receptors, and the central neurons that receive signals from them, have evolved to provide organisms with information that is useful in guiding their behaviour. ‘Information’ must be defined not only mathematically, but it terms of behavioural significance. Any biological interpretation of sensory processing would, then, emphasise the value of its conclusions—reverse-engineered, inductive inferences about the nature of things and events in the outside world (and within the animal). In those terms it is not at all surprising that perception is multisensory: integration of information from different senses can provide more reliable evidence about the location and nature of events. What is surprising is that we are aware of the raw, unimodal elements of experience (Block’s phenomenal consciousness; qualia), which don’t seem to matter in terms of behaviour. If I spot a ripe strawberry and pick it, what matters is the knowledge that it is a strawberry and that it is ripe. Activation of red-catching cones in my retina helps me with that identification, but why do I need to experience the redness directly?
What is even more remarkable, given the evident mingling of sensory information, is how robust the phenomenal awareness of the modality of experiences seems to be. Recently, Yuanyuan Zhao and I have been testing the apparent robustness of the modal ‘tagging’ of sensory experience. In detection tasks in which the stimulus is either a flash of light or a sound beep, in random sequence, there is, surprisingly, no difference in threshold or certainty of awareness for each modality compared with control experiments with stimuli of only one modality. And, even more surprising, the modality can be identified more reliably than the stimulus can be detected. Observers are remarkably reliable at identifying the modality of a stimulus, even when they are unsure that they have had a sensory experience.
From a functional perspective, why should I be so distinctly aware that the shape, colour and location of a strawberry are visual experiences, while its odour is an olfactory experience, when both help me to identify it as a strawberry?
Even though different components of a visual experience (shape, colour, motion, depth etc) seem to depend on explicit representation in different regions of extrastriate visual cortex, they all share the same modal sense of being visual. Since virtually all visual signals arrive at the primary visual cortex (V1) and are then distributed to extrastriate regions, is it possible that the awareness of modality ‘arises’ in V1, even if the content of experience depends on explicit representation in the activity of neurons outside V1.
- Barlow, H. B. (1972), ‘Single units and sensation: a neuron doctrine for perceptual psychology’, Perception 1: 371–94
- Pennartz, C. M. A. (2009), ‘Identification and integration of sensory modalities: neuronal basis and relation to consciousness’, Consciousness & Cognition 18: 718–93