Why the Principle of the Identity of Indiscernibles is not contingently true either

Faced with strong arguments to the effect that Leibniz'sPrinciple of the Identity of Indiscernibles (PII) is not a necessary truth, many supporters of the Principle have staged a strategic retreat to the claim that it is contingently true in this, the actual, world. The purpose of this paper is to examine the status of the various forms of PII in both classical and quantum physics, and it is concluded that this latter view is at best doubtful, at worst, simply wrong.I would like to thank Michael Redhead and an anonymous referee for several useful suggestions and criticisms relating to the earlier version of this paper. I must also acknowledge the support given by the Centre of Logic, Epistemology and History of Science of the University of Campinas and the Brazilian National Council for Scientific and Technological Development in the later stages of the preparation of this work.     

Mental health expert witnesses: Of science and crystal balls

This article reviews the history of and basis for mental health testimony. It surveys the roles of such experts in the legal system and the concomitant problems with current approaches. Finally, it suggests specific reforms that may improve the use of mental health experts in legal proceedings.     

Automated data collection using bar code

Using bar code technology to automate data collection provides a rapid and reliable alternative to paper-and-pencil tracking or keyboard entry into pocket or laptop computer. An array of bar code symbols is printed on a data menu, with a unique symbol corresponding to each possible observation. Bar code symbols are scanned using hand-held readers, which record the event, log the observation time, and store data for transfer to a personal computer. Advantages of the bar code monitoring system include: (1) ease of use by staff with minimal technical training, (2) reduced data entry errors and increased entry speed, (3) reliable portable operation, and (4) low-cost hardware. While the bar code system described here is used for behavioral monitoring in a residential treatment setting for the developmentally disabled, with minimal modification this system can be adapted for use in a wide variety of research and clinical applications.     

Conversational skills for autistic adolescents: An autistic peer as prompter

In this study, an autistic youth served as peer prompter for three other autistic adolescents. The peer prompter encouraged the other boys to talk about sports, a topic frequently discussed by typical teenagers. A multiple-baseline design across participants was used to assess the effectiveness of the peer-prompting procedure. During baseline, the youth rarely talked about sports, although all three had previously completed a sports-appreciation class and had displayed large pre-to-post gains on a paper-and-pencil test. During intervention, when a peer prompted sports discussions, all three youth engaged in much more sports-related conversation. Generalization measures indicated that: (1) the youth engaged in sports discussions in groups, as well as in the dyads that characterized the training situation; (2) they talked about sports in a setting other than the training setting; (3) they discussed sports with their peers when an unfamiliar teacher was present; and (4) they continued to discuss sports when training tapes and behavioral contracts between the teacher and the peer prompter were withdrawn. Previously, it has been common to use nonhandicapped or less-handicapped peers as tutors; this study demonstrates that an autistic youth may also effectively serve as a prompter who assists his schoolmates in acquiring conversational skills that contribute to their normalization.     

The sensitivity of the Bender-Gestalt Test as a screening instrument for neuropsychological impairment in older adults

We investigated the sensitivity of the Bender (1938) Visual-Motor Gestalt Test (BGT) using the Halstead-Reitan Neuropsychological Battery (HRB) as the criterion for cortical dysfunction. We studied 95 subjects over age 55 who had been diagnosed as having dementia or pseudodementia. Subjects were classified as mild, moderately, or severely impaired on the HRB and as impaired or unimpaired on the BGT. The results indicated that the BGT is less sensitive (36%) than was expected when used on an impaired geriatric population. The data further indicated that false negatives occurred more frequently with the BGT when individuals had mild neuropsychological impairment. Less frequent misclassifications occurred as the severity of impairment on HRB indices increased.     

The negative priming effect: Inhibitory priming by ignored objects

A priming paradigm was employed to investigate the processing of an ignored object during selection of an attended object. Two issues were investigated: the level of internal representation achieved for the ignored object, and the subsequent fate of this representation. In Experiment 1 a prime display containing two superimposed objects was briefly presented. One second later a probe display was presented containing an object to be named. If the ignored object in the prime display was the same as the subsequent probe, naming latencies were impaired. This effect is termed negative priming. It suggests that internal representations of the ignored object may become associated with inhibition during selection. Thus, selection of a subsequent probe object requiring these inhibited representations is delayed. Experiment 2 replicated the negative priming effect with a shorter inter-stimulus interval. Experiment 3 examined the priming effects of both the ignored and the selected objects. The effect of both identity repetition and a categorical relationship between prime and probe stimuli were investigated. The data showed that for a stimulus selected from the prime display, naming of the same object in the probe display was facilitated. When the same stimulus was ignored in the prime display, however, naming of it in the probe display was again impaired (negative priming). That negative priming was also demonstrated with categorically related objects suggests that ignored objects achieve categorical levels of representation, and that the inhibition may be at this level.     

Selective attention and priming: Inhibitory and facilitatory effects of ignored primes

The priming effects of ignored information have been studied in Stroop displays (Neill, 1977) and with spatially superimposed drawings (Tipper, in this issue); naming of probes related to ignored primes is delayed in these experiments (“negative priming”). This negative priming effect is confirmed in a list reading task in Experiment 1, which used partially superimposed letters, and Experiment 2, which used spatially separated letters. Furthermore, Lowe (1979) using Stroop colour words observed that changing the nature of the probe such that it did not require selection from a competing word reversed the priming effects of the ignored word from inhibition to facilitation. Experiment 3 confirmed this observation when subjects selected a red letter from a green letter. Two models are suggested to account for this result. In the first, negative priming is a product of the ignored prime and subsequent probe being encoded both as a stimulus to be ignored and one to be named (Allport, Tipper and Chmiel, in press; Lowe, in press). This dual encoding is ambiguous, requiring further processing before response can be output. The other model suggests that negative priming reflects inhibition of response to ignored information, slowing naming latencies to probe stimuli that require the same response. Experiment 4 attempts to differentiate between the models, and the latter inhibition view is preferred.     

Motivation and performance: Two consequences of winning and losing in competition

The present study examined the effects of competitive outcome—either a win or a loss—on intrinsic motivation. Winning was hypothesized to facilitate both performance and intrinsic motivation. Fifty-four participants, 29 females and 25 males, competed against a same-gender confederate in a puzzle-solving contest. Following the competition, participants' intrinsic motivation was surreptitiously measured by the amount of time spent playing with the puzzle while alone. Results showed that winning facilitated both actual competitive performance and intrinsic motivation relative to losing. The importance of considering the outcome when predicting intrinsic motivation after competition is discussed.     

Implications of memory and language dysfunction in the naming deficit of senile dementia

Young normals, elderly normals, and patients with either mild-to-moderate or severe senile dementia of the Alzheimer type (SDAT) were administered several tests of language function and remote memory. On all of the language tests examined, elderly normals exhibited a mild, nonsignificant performance decrement relative to the young normals. Advanced SDAT patients were markedly impaired on all of the tests. Early dementia patients were most impaired, relative to aged normals, on tests of object naming, category instance fluency, and remote memory. The deficit was smaller on the WAIS vocabulary subtest, on selecting the name of a visually presented object, and on recalling the function of an object. Early SDAT patients were least impaired in selecting the picture of an object after its name had been provided and in selecting objects that belong to a specified functional category. The results are consistent with the notion that the language dysfunction in early SDAT is due to a deficit in semantic memory function in which general, categorical information remains available whereas information about specific attributes becomes less accessible. The object naming test might be useful in the assessment of treatment effects upon SDAT because of its sensitivity and specificity to dementia, its high face validity, and its independence of recent memory.