A simulation-based tutorial system for exploring parallel distributed processing

This article presents a simulation-based tutorial system for exploring parallel distributed processing (PDP) models of information processing. The system consists of software and an accompanying handbook. The intent of the package is to make the ideas underlying PDP accessible and to disseminate some of the main simulation programs that we have developed. This article presents excerpts from the handbook that describe the approach taken, the organization of the handbook, and the software that comes with it. An example is given that illustrates the approach we have taken to teaching PDP, which involves presentation of relevant mathematical background, together with tutorial exercises that make use of the simulation programs.     

Distributed memory and the representation of general and specific information

We describe a distributed model of information processing and memory and apply it to the representation of general and specific information. The model consists of a large number of simple processing elements which send excitatory and inhibitory signals to each other via modifiable connections. Information processing is thought of as the process whereby patterns of activation are formed over the units in the model through their excitatory and inhibitory interactions. The memory trace of a processing event is the change or increment to the strengths of the interconnections that results from the processing event. The traces of separate events are superimposed on each other in the values of the connection strengths that result from the entire set of traces stored in the memory. The model is applied to a number of findings related to the question of whether we store abstract representations or an enumeration of specific experiences in memory. The model simulates the results of a number of important experiments which have been taken as evidence for the enumeration of specific experiences. At the same time, it shows how the functional equivalent of abstract representations--prototypes, logogens, and even rules--can emerge from the superposition of traces of specific experiences, when the conditions are right for this to happen. In essence, the model captures the structure present in a set of input patterns; thus, it behaves as though it had learned prototypes or rules, to the extent that the structure of the environment it has learned about can be captured by describing it in terms of these abstractions.     

The relationship of affiliative arousal to dopamine release

Higher levels of affiliation motivation after exposure to affiliative films are significantly related to higher dopamine concentrations in saliva in one study of 61 college students of both sexes, and in plasma in another study of 47 adults of both sexes. Individuals high in dispositionaln Affiliation, if they also reported high life stress, showed high gains in dopamine concentration in plasma after exposure to an affiliative film significantly more often than other individuals. Since aroused affiliation motivation was not associated with higher concentrations of norepinephrine, epinephrine, or cortisol in either study, it appears likely that dopamine is especially associated with arousal of affiliation motivation, just as norepinephrine has been found to be associated with arousal of power motivation. Thus, different motives may be subserved by different hormones, making it unlikely that all motives lead to the same state of physiological arousal.This research was carried out when all the authors were connected with the Department of Psychology and Social Relations at Harvard University. We acknowledge with thanks the support of the John D. and Catherine T. MacArthur Foundation through a grant to the senior author.     

Some reflections on the two psychologies of love

The mainstream view of love is that it is a state that arises from people mutually reinforcing each other or providing benefits to each other Yet careful quantitative analyses of imaginative thought patterns of people in love or in a state of affiliative arousal reveal themes of dialogue, commitment, and harmony rather than of mutual benefits It is suggested that asking people about love leads them to give causal explanations for the state which psychologists have elaborated into the theory that love is a response to having one's needs met Imaginative experiences characteristic of the state of being in love on the other hand may be different because they are primarily right brain mediated and do not share in the causal, instrumental type of reasoning characteristic of left brain conscious thinking Such conceivably right brain mediated experiences in TATs are more closely associated than presumably left brain mediated self-reports are with such physiological measures as evoked scalp potentials, neurohormone concentrations, and immune functions A vew of love that takes both self-report (left brain) and fantasy (right brain) measures into account does a better job of predicting affiliative behavior than does a view that relies solely on one or the other of the two types of measures     

Perceptual interactions in two-word displays: familiarity and similarity effects

Previous studies have demonstrated the existence of perceptual interactions in the processing of two-word displays such as SAND LANE. When postcued to report one of the two words, subjects often make migration errors, in that the report of the specified word includes a letter of the other word (e.g., LAND or SANE instead of SAND). We find that migrations depend on the abstract, structural similarity of the strings, but not on the physical similarity; on whether the strings are words; and on whether the possible migration responses are words. We also rule out an interpretation of migration errors that attributes them to a guessing strategy. Our findings are interpreted in terms of models in which both strings simultaneously access high-level structural knowledge, that is, knowledge about what sequences of letters fit together to form familiar wholes.     

Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.     

Achievement motivation in relation to achievement-related recall,performance, and urine flow,a marker associated with release of vasopressin

Administration of the pituitary hormone, arginine vasopressin (AVP), enhances memory in animals and humans. Since AVP is the antidiuretic hormone, its release can be inferred from reductions in urine flow. Forty-six male adults recalled the contents of a complex story and then either were exposed to achievement arousal or were not. Significantly more of the subjects in the aroused than the nonaroused condition showed a decrease in urine flow, and the greater the decrease in urine flow among the achievement-aroused subjects, the better the recall of achievement-related story content 24 hours later. Subjects high inn Achievement, in the achievement-oriented condition, showed lower urine output at the outset of the second day and greater improvement in learning to unscramble words. Since lower urine output was also related to improvement in unscrambling words, achievement arousal may have released AVP which in turn may have facilitated achievement-related retention and performance.I am greatly indebted to Sean Connelly for assistance in carrying out this research and to Dr. Franklin Epstein of the Beth Israel Hospital, Boston, for helping me to understand how the kidney functions in producing urine.     

Promoting Energy Conservation in Master-Metered Apartments through Group Financial Incentives1

An energy conservation contest among four groups of apartments (44 to 70 units each) in a University of Colorado family housing complex was conducted February-April, 1977. The winning group in each of six 2-week contests won $80 to use however it determined. The program produced a drop of about 10% in use of natural gas during the first contest; energy savings were smaller but still statistically significant throughout the first 8 weeks. Over a 12-week period, savings averaged 6.6%. Some changes in energy-using behaviors were reported by residents surveyed at the contest's end; however, knowledge of contest results by residents was minimal. The results are compared to those of other contest and rebate programs, the practical problems of costs exceeding savings and inaccurate estimates of energy savings are discussed, and implications for future research are suggested.     

Two mechanisms of human contingency learning

How do humans learn contingencies between events? Both pathway-strengthening and inference-based process models have been proposed to explain contingency learning. We propose that each of these processes is used in different conditions. Participants viewed displays that contained single or paired objects and learned which displays were usually followed by the appearance of a dot. Some participants predicted whether the dot would appear before seeing the outcome, whereas other participants were required to respond quickly if the dot appeared shortly after the display. In the prediction task, instructions guiding participants to infer which objects caused the dot to appear were necessary in order for contingencies associated with one object to influence participants' predictions about the object with which it had been paired. In the response task, contingencies associated with one object affected responses to its pair mate irrespective of whether or not participants were given causal instructions. Our results challenge single-mechanism accounts of contingency learning and suggest that the mechanisms underlying performance in the two tasks are distinct.     

Generalization through the recurrent interaction of episodic memories: a model of the hippocampal system

In this article, we present a perspective on the role of the hippocampal system in generalization, instantiated in a computational model called REMERGE (recurrency and episodic memory results in generalization). We expose a fundamental, but neglected, tension between prevailing computational theories that emphasize the function of the hippocampus in pattern separation (Marr, 1971; McClelland, McNaughton, & O'Reilly, 1995), and empirical support for its role in generalization and flexible relational memory (Cohen & Eichenbaum, 1993; Eichenbaum, 1999). Our account provides a means by which to resolve this conflict, by demonstrating that the basic representational scheme envisioned by complementary learning systems theory (McClelland et al., 1995), which relies upon orthogonalized codes in the hippocampus, is compatible with efficient generalization-as long as there is recurrence rather than unidirectional flow within the hippocampal circuit or, more widely, between the hippocampus and neocortex. We propose that recurrent similarity computation, a process that facilitates the discovery of higher-order relationships between a set of related experiences, expands the scope of classical exemplar-based models of memory (e.g., Nosofsky, 1984) and allows the hippocampus to support generalization through interactions that unfold within a dynamically created memory space.