Investigation of the intersection of constraints model of motion perception

The direction and speed of motion of a one-dimensional (1-D) stimulus, such as a grating, presented within a circular aperture is ambiguous. This ambiguity, referred to as the Aperture Problem (Fennema & Thompson, 1979) results from (i) the inability to detect motion parallel to grating orientation, and (ii) the occlusion of border information, such as the ‘ends’ of the grating, by the surface forming the aperture, Adelson and Movshon's (1982) intcrsection-of-constraints (IOC) model of motion perception describes a two-stage method of disambiguating the motion of 1-D moving stimuli (e.g., gratings) to produce unambiguous motion of two-dimensional (2-D) objects (e.g., plaid patterns) made up of several 1-D components. Specifically, in the IOC model ambiguous 1-D motions extracted by Stage 1 component-selective mechanisms are integrated by Stage 2 pattern-selective mechanisms to produce unambiguous 2-D motion signals. ‘Integration’ in the context of the IOC model involves determining the single motion vector (i.e., combination of direction and speed) which is consistent with the I-D components of a 2-D object. Since the IOC model assumes that 2-D objects undergo pure translation (i.e., without distortion, rotation, etc.), the motion vector consistent with all 1-D components describes the motion of the 2-D object itself. Adelson and Movshon (1982) propose that neural implementation of the computation underlying the IOC model is reflected in the perception of coherent 2-D plaid motion reported when two separately-moving ‘component’ gratings are superimposed. Using these plaid patterns the present thesis assesses the IOC model in terms of its ability to account for the perception of 2-D motion in a variety of circumstances. In the first series of experiments it is argued that the unambiguous motion perceived for a single grating presented within a rectangular aperture (i.e., the Barberpole illusion; Wallach, 1976) reflects application of the IOC computation to the moving 1-D grating and the stationary boundary of the aperture. While contrary to the assumption which underlies the IOC model (viz., that integration occurs between moving 1-D stimuli), evidence consistent with the involvement of the IOC computation in mediating the Barberpole illusion (in which there is only one moving stimulus) is obtained by measuring plaid coherence as a function of aperture shape. It is found that rectangular apertures which bias perceived component motions in directions consistent with plaid direction facilitate plaid coherence, while rectangular apertures which bias perceived component motions in directions inconsistent with plaid direction disrupt plaid coherence. In the second series of experiments, perceived directions of motion of type I symmetrical, type I asymmetrical, and type II plaids are measured with the aim of investigating the deviations in plaid directions reported by Ferrera and Wilson (1990) and Yo and Wilson (1992). Perceived directions of both asymmetrical and type II plaids are shown to deviate away from lOC-predicted directions and towards mean component direction. Furthermore, the magnitude of these deviations is being proportional to the difference between lOC-predicted plaid direction and mean component direction. On the basis of these directional deviations, modification to the IOC model is proposed. In the modified IOC model it is argued that plaid perception involves (i) the activity of Stage 2 pattern-selective mechanisms (and the Stage 1 component-selective mechanisms which input into these pattern-selective mechanisms) involved in implementing the IOC computation, and (ii) component-selective mechanisms which influence plaid perception directly, and ‘extraneously’ to the IOC computation. In the third series of experiments the validity of this modified IOC model, as well as the validity of alternative one-stage models of plaid perception are assessed in relation to perceived directions of plaid-induced MAEs as a function of both plaid direction and mean component direction. It is found that plaid-induced MAEs are shifted away from directions opposite to lOC-predicted plaid direction towards the direction opposite to mean component direction. This pattern of results is taken to be consistent with the modified IOC model which predicts the activity, and adaptation both of mechanisms signalling plaid direction (via implementation of the IOC computation), and ‘extraneous-type’ component-selective mechanisms signalling component directions. Alternative one-stage models which predict the adaptation of only mechanisms signalling plaid direction (the feature-tracking model), or the adaptation only of mechanisms signalling component directions (the distribution-of-activity model), cannot account for the directions of plaid-induced MAEs reported. The ability of the modified IOC model to account for the perceived directions of (i) gratings in rectangular apertures, (ii) various types of plaid in circular apertures, and (iii) directions of plaid-induced MAEs, is interpreted as supporting the proposition that human motion perception is based on a parallel and distributed process involving Stage 2 pattern-selective mechanisms (and the Stage 1 component-selective mechanisms which input into these mechanisms) taken to implement the IOC computation, and component-selective mechanisms taken to provide an 'extraneous' direct contribution to motion perception.

Physical theory of organisation and consequent neural model of spatio-temporal pattern acquisition

A neurone model (the FORMON) is proposed which provides a mathematical explanation for a range of psychological phenomena and has potential in Artificial Intelligence applications. A general definition of organisation in terms of entropy and information is formulated. The concept of microcodes is introduced to describe the physical nature of organisation. Spatio-temporal pattern acquisition and processing functions attributable to individual neurones are reviewed. The criterion for self-organisation in a neurone is determined as the maximisation of mutual organisation. A feedback control system is proposed to satisfy this criterion and provide an integrated long-term memory of spatio-temporal pattern. This pattern acquisition system is shown to be applicable to dendritic pattern recognition and axonal pattern generation. Provision is also made for adaptation, short-term memory and operant learning. An electro-chemical model of transmission and processing of neural signals is outlined to provide the pattern acquisition functions of the Formon model. A transverse magnetic mode of electrotonic propagation is postulated in addition to the transverse electromagnetic mode. Configurations of the Formon are categorised in terms of possible pattern processing functions. Connective architectures are proposed as self-organising models of acquisitive semantic and syntactic networks.

Are individual differences in temperament of relevance to Gibson's theory of affordances?

The ambitious scope, complexity, and difficulty of Gibson’s project in proposing the theory of affordances are captured nicely by the words of Gibson’s biographer, Ed Reed:
“Gibson was convinced that the theory of affordances, in
conjunction with the concepts of information, persistence, and
change, would enable him to transcend the ancient debate between
subjectivity and objectivity and to resolve the mind-body problem. …
[H]e was offering a new approach to problems of psychology, one
that he believed would not sink in the morass that have engulfed
previous psychologies.” (Reed, 1988, p. 280).
These characteristics of the theory of affordances are further evidenced in the debates about the nature of affordances presented in the suite of papers in Ecological Psychology, Volume 12(1). In this paper we propose an elaboration of the notion of affordance by suggesting that those persisting individual differences in behaviour described as temperamental differences (e.g., differences on a dimension of temperament anchored at one end by behaviour described as ‘outgoingness’ and at the other by behaviour described as ‘avoidance’) can be integrated into the theory of affordances. We argue that such integration is consistent with Gibson’s project as reflected in Reed’s words, and as part of our argument, draw parallels between the integration of temperament with the theory of affordances and the way in which individual differences in body dimensions are incorporated in the theory. We also outline some empirical tests of our proposition.

Robert Boyle's theory of nature, with reference to his understanding of natural laws

Argues that the theory of nature-cum-theology and the view of of natural laws of the 17th century natural philosopher, Robert Boyle, were more complex and eclectic than is usually believed. Support is given for construing Boyle as a more complex thinker than previous scholars have suggested.

National interest in the theory of international relations

The concept of "the national interest" has been widely analysed by historians and political scientists. However, there has not been a systematic investigation of the term from the range of theoretical perspectives which comprise the discipline of International Relations. This dissertation fills this gap by examining how the term is variously understood by realist, Marxist, anarchist, liberal, rationalist and constructivist theories of International Relations. It is argued that far from having a clear and unambiguous meaning, "the national interest" is a problematic term which is largely devoid of substantive content.

Theory of planned behaviour and implementation intentions in dental attendance

The thesis used a model of health behaviour to examine the predictors of dental attendance. Older respondents who had strong intentions, low perceived vulnerability, stable plans to attend, and were influenced by significant others were more likely to have attended the dentist for preventive care in the last 12 months. The portfolio concludes that attachment theory is a useful conceptual framework for enhancing our understanding of the antecedents and consequences of childhood sexual abuse.

Crash landing at INSEAD : initiating a grounded theory of the pedagogical effectiveness of simulation games for teaching aspects of entrepreneurship

A practical teaching difficulty arising in a conducive environment provided opportunity to turn the particular problem into a case study with generic implications. Little research has been conducted on the use or effectiveness of simulation games for teaching entrepreneurship. In the context of established literature critiquing the effectiveness of simulation games as teaching devices in managerial contexts and at a point where problems in using a simulation game as part of entrepreneurship course became evident, the authors designed and executed a single-case research project to generate initial theoretical propositions about the pedagogical effectiveness of simulation games for teaching various concepts and aspects of entrepreneurship. The case analysed the perceived learning environment created when the Sky-High simulation was played by 41 MBA students taking an elective entrepreneurship course at INSEAD. The research design embodied the established methodological principles specified by Yin (1989), for effective case research. Theory building was based upon the grounded-theorizing procedures articulated by Glaser and Strauss (1967). Analysis and synthesis produced a grounded theory, in the form of a normative argument, containing four attribute categories and associated properties required of a simulation game to make it an efficacious teaching device in entrepreneurship contexts. The establishment of this grounded theory has made it both desirable and feasible to contemplate creation of an ISO quality standard for educational simulation games.

A grounded theory of intuition among occupational therapists in mental health practice

Objectives: This study aimed to explore occupational therapists’ understanding and use of intuition in mental health practice.
Method: Using a grounded theory approach, a theoretical sample of nine occupational therapists practising in mental health settings participated in semi-structured interviews. Data were analysed using the constant comparative method.
Findings: Intuition was found to be embedded within clinical reasoning. From the data, intuition was defined as knowledge without conscious awareness of reasoning. The participants viewed intuition as elusive and underground, and suggested that professional experience led to a more comfortable use of intuition. Using intuition relied on therapists’ understanding of their own and others’ emotions, and intuition partnered analysis within their clinical reasoning. A grounded theory of the use of intuition in mental health settings is proposed.
Conclusion: Occupational therapists practising in mental health settings understand intuition to be an instinctive understanding of situations, resulting from their professional experience and the understanding of emotions.