Bar holding during escape conditioning

To analyze bar-holding behavior during escape conditioning three rats were trained to escape from shock by pressing a bar, and three were trained to escape by releasing a bar. Bar holding behavior was stronger and more stable under the release condition. These effects were related to the relative shock duration of onbar versus offbar shocks.     

The use of rats as discriminative stimuli

A FREE OPERANT PROCEDURE WAS USED TO DETERMINE WHETHER OR NOT ONE RAT COULD DISCRIMINATE: (1) between the presence and absence of a second rat, and (2) between two other rats of the same species and sex. The subjects were four male Wistar rats. The discriminatory response was a bar press and food was used as reinforcement during training. Although there were wide individual differences in rate of learning, all subjects learned to make both discriminations.     

Heading and path information from retinal flow in naturalistic environments

In four experiments, we explored the heading and path information available to observers as we simulated their locomotion through a cluttered environment while they fixated an object off to the side. Previously, we presented a theory about the information available and used in such situations. For such a theory to be valid, one must be sure of eye position, but we had been unable to monitor gaze systematically; in Experiment 1, we monitored eye position and found performance best when observers fixated the designated object at the center of the display. In Experiment 2, when we masked portions of the display, we found that performance generally matched the amount of display visible when scaled to retinal sensitivity. In Experiments 3 and 4, we then explored the metric of information about heading (nominal vs. absolute) available and found good nominal information but increasingly poor and biased absolute information as observers looked farther from the aimpoint. Part of the cause for this appears to be that some observers perceive that they have traversed a curved path even when taking a linear one. In all cases, we compared our results with those in the literature.     

“Make things as simple as possible, but no simpler.” A rejoinder to Scruggs and Mastropieri

Scruggs and Mastropieri (Behaviour Research and Therapy, 32, 879–883, 1994) take issue with criticisms of their PND (Percent of Nonoverlapping Data) statistic that we offered in our recent article (Allison & German, Behaviour Research and Therapy, 31, 621–631, 1993), which advocated a regressionbased method for obtaining effect sizes in single-subject studies. They contend that their PND approach has several advantages over our approach because: (1) they believe that, unlike ours, it can take advantage of the small number of observations that are typically available in single-case studies; (2) it is simple to compute; (3) it frees researchers from traditional regression assumptions of normality, homogeneity of variance, and independence of observations and residuals; and (4) it correlates with visual judgements made by experts. As we shall argue, these claims are built upon very questionable assumptions and they are very difficult to substantiate. In addition, we show that the expected value of the PND is so strongly related to sample size as to be rendered meaningless.     

REFLECTIONS ON AFFIRMATIVE ACTION GOALS IN PSYCHOLOGY ADMISSIONS

Four goals of affirmative action in higher education are described as they relate to psychology admissions. Broadly conceived, these goals are compensating for past injustice, correcting present inequity, promoting intellectual diversity, and enhancing the presence of role models. It is argued that the four goats differ in their underlying assumptions about the purposes of affirmative action and that these differences can result in disparate admission decisions. Data from three experiments on decision making in graduate psychology admissions are presented to illustrate the analysis. In these studies, academic psychologists rated the admissibility of hypothetical graduate student applicants who varied on a number of characteristics (e g., ethnicity, social class, interest in minority research) pertinent to affirmative action. A consistent pattern of ethnic group differences in admissibility ratings was documented, illustrating that compensation for past injustice can be interpreted as a salient affirmative action goal in graduate admissions decisions. Implications of the analysis for clarifying admissions decisions guided by affirmative action goals are discussed.     

Comparison between Oral and Written Spelling in Alzheimer's Disease

Written and oral spelling were compared in 33 patients with Alzheimer's disease (AD) and 25 control subjects. AD patients had poorer spelling results which were influenced by orthographic difficulty and word frequency, but not by grammatical word class. Lexical spelling was also more deteriorated than phonological spelling. Moreover, oral spelling was more impaired than written spelling in AD patients, whereas no difference was present between oral and written spelling of controls. Analysis of spelling errors showed that, for controls, errors were predominantly phonologically accurate in both spelling tasks. Significantly, AD patients produced more phonologically accurate than inaccurate errors in written spelling, whereas these errors did not differ in oral spelling. In contrast to controls who produced more constant than variable responses in oral and written spelling, AD patients made more variable responses (words correctly spelled in one task but incorrectly in the other) and they showed many instances of variable errors (different misspellings from one spelling task to the other). Two stepwise regression procedures showed that written misspellings were specifically correlated with language impairment, whereas oral spelling errors were correlated with attentional and language disorders. These results suggest that AD increases the attentional demands of oral spelling process as compared to written spelling. This dissociation argues, either for a unique Graphemic Buffer in which oral spelling requires more attentional resources than written spelling or for the hypothesis of separate buffers for oral and written spelling.