The efficiency of biological motion perception

Humans can readily perceive biological motion from point-light (PL) animations, which create an image of a moving human figure by tracing the trajectories of a small number of light points affixed to a moving human body. We have applied ideal observer analysis to a standard biological motion discrimination task involving either full-figure or PL displays. Contrary to current dogma, we find that PL animations can be rich inpotential stimulus information but that human observers are remarkably inefficient at exploiting this information. Although our findings do not discount the utility of PL animation, they do provide a realistic measure of the computational challenge posed by biological motion perception.     

Congruity Effects in Time and Space: Behavioral and ERP Measures

Two experiments investigated whether motion metaphors for time affected the perception of spatial motion. Participants read sentences either about literal motion through space or metaphorical motion through time written from either the ego-moving or object-moving perspective. Each sentence was followed by a cartoon clip. Smiley-moving clips showed an iconic happy face moving toward a polygon, and shape-moving clips showed a polygon moving toward a happy face. In Experiment 1, using an explicit judgment task, participants judged smiley-moving cartoons as related to ego-moving sentences about space and about time, and shape-moving cartoons as related to object-moving sentences. In Experiment 2, participants viewed the same stimuli, but the cartoons were task-irrelevant. Event-related brain potentials revealed an early attentional effect of congruity on cartoons following sentences about space, and a later semantic effect on cartoons following sentences about time. Results are most consistent with accounts that posit differences in the processing of novel and conventional metaphors.     

Between-language repetition priming in antonym generation: evidence that translation-equivalent adjectives have shared conceptual representations across languages

Previous literature has demonstrated conceptual repetition priming across languages in bilinguals. This between-language priming effect is taken as evidence that translation equivalents have shared conceptual representations across languages. However, the vast majority of this research has been conducted using only concrete nouns as stimuli. The present experiment examined conceptual repetition priming within and between languages in adjectives, a part of speech not previously investigated in studies of bilingual conceptual representation. The participants were 100 Spanish-English bilinguals who had regular exposure to both languages. At encoding, participants performed a shallow processing task and a deep-processing task on English and Spanish adjectives. At test, they performed an antonym-generation task in English, in which the target responses were either adjectives presented at encoding or control adjectives not previously presented. The measure of priming was the response time advantage for producing repeated adjectives relative to control adjectives. Significant repetition priming was observed both within and between languages under deep, but not shallow, encoding conditions. The results indicate that the conceptual representations of adjective translation equivalents are shared across languages.     

The value hypothesis and acquisition of preference in concurrent chains

Experiment 1 compared the acquisition of initial- and terminal-link responding in concurrent chains. The terminal-link schedules were fixed interval (FI) 10 sec and FI 20 sec, but some presentations were analogous to no-food trials in the peak procedure, lasting 60 sec with no reinforcement delivery. Pigeons completed a series of reversals in which the schedules signaled by the terminal-link stimuli (red and green on the center key) were changed. Acquisition of temporal control of terminal-link responding (as measured by peak location on no-food trials) was more rapid than acquisition of preference in the initial links. Experiment 2 compared acquisition in concurrent chains, using the typical procedure in which the terminal-link schedules are changed with a novel arrangement in which the initial-link key assignments were changed while the terminal-link schedules remained the same. Acquisition of preference was faster in the latter condition, in which the terminal-link stimulus-reinforcer relations were preserved. These experiments provide the first acquisition data that support the view that initial-link preference is determined by the values of the terminal-link stimuli.     

Acquisition of preference in concurrent chains: comparing linear-operator and memory-representational models

Two experiments were conducted to test predictions of 2 models for acquisition of preference in concurrent chains. Pigeons were trained with pairs of fixed-interval and variable-interval terminal-link schedules in a successive-reversal design. Results showed that acquisition rate was faster when fixed-interval schedules preceded and when variable-interval schedules followed the reversal and was approximately constant when the same pair of schedules was used. These results were predicted by both linear-operator and memory-representational models. However, only the linear-operator model predicted effects of schedule duration. Overall, these results demonstrated that a simple linear-operator model can account for the major features of preference acquisition in concurrent chains and suggest that choice in transition and steady state may provide convergent validation of a single delay-discounting function.     

Religion and emotional compensation: results from a prospective study of widowhood

Based on recent applications of attachment theory to religion, the authors predicted that the loss of a spouse would cause widowed individuals to increase the importance of their religious/spiritual beliefs. This hypothesis was examined using the Changing Lives of Older Couples sample from which preloss measures of religiosity were available for widowed individuals and matched controls. A total of 103 widowed individuals provided follow-up data, including reports of religious beliefs and grief, at 6 months, 24 months, and 48 months after the loss. Results indicated that widowed individuals were more likely than controls to increase their religious/spiritual beliefs. This increase was associated with decreased grief but did not influence other indicators of adjustment such as depression. Finally, insecure individuals were most likely to benefit from increasing the importance of their beliefs. Results are discussed in terms of the potential value of applying psychological theory to the study of religion.     

Placebo: Its action and place in health research today

The place for the placebo in human clinical research is addressed in this paper. The World Medical Association which is comprised of some 80 National Medical Associations uses much of its resources to address medical ethics and human rights issues. It adopted the Declaration of Helsinki in June 1964 which addressed the protection of individuals in clinical trials. The use of placebos assumes an important role in this document. Five Revisions of the Declaration of Helsinki have occurred and the most recent was adopted in October 2000. The provisions on placebo are now in Paragraph 29 which reads as follows: “The benefit, risks, burdens and effectiveness of a new method should be tested against those of the best current prophylactic, diagnostic and therapeutic methods. This does not exclude the use of placebo, or no treatment, in studies where no proven prophylactic, diagnostic or therapeutic methods exists.” The reactions to the newly revised version of the Declaration of Helsinki were numerous and rapid, not the least of which was the paragraph I quoted above. At the direction of the WMA Council, a small group of experts together with the WMA workgroup studied the Paragraph 29 to ensure that no ethically sound research was being restricted by the revision. The outcome was approved by the Council and later the WMA General Assembly in October 2000. This gives a note of clarification as to the appropriate use of placebos. Numerous papers and statements over the last several years have described positions very much in line with the Note of Clarification cited above. This paper was presented at an international conference, “Placebo: Its Action and Place in Health Research Today,” held in Warsaw, Poland on 12–13 April, 2003.