Human echolocation: pitch versus loudness information

Blind persons emit sounds to detect objects by echolocation. Both perceived pitch and perceived loudness of the emitted sound change as they fuse with the reflections from nearby objects. Blind persons generally are better than sighted at echolocation, but it is unclear whether this superiority is related to detection of pitch, loudness, or both. We measured the ability of twelve blind and twenty-five sighted listeners to determine which of two sounds, 500 ms noise bursts, that had been recorded in the presence of a reflecting object in a room with reflecting walls using an artificial head. The sound pairs were original recordings differing in both pitch and loudness, or manipulated recordings with either the pitch or the loudness information removed. Observers responded using a 2AFC method with verbal feedback. For both blind and sighted listeners the performance declined more with the pitch information removed than with the loudness information removed. In addition, the blind performed clearly better than the sighted as long as the pitch information was present, but not when it was removed. Taken together, these results show that the ability to detect pitch is a main factor underlying high performance in human echolocation.     

Randomized controlled trial of brief interventions to reduce college students' drinking and risky sex

The present study tested the proposition that an intervention to reduce alcohol use among college students will also reduce their risky sexual behavior. In a randomized controlled trial, 154 heavy-drinking, predominantly White, heterosexual college students at behavioral risk for infection with HIV and other sexually transmitted diseases were assigned to receive no intervention or a two-session, in-person, motivational interviewing-based intervention focused on (a) reducing alcohol risk behavior, (b) reducing HIV risk behavior, or (c) reducing both alcohol and HIV risk behavior. Three-month retrospective assessments of alcohol use and sexual behavior were conducted at intake and at 3-, 6-, 9-, 12-, and 15-month follow-up appointments. During follow-up, participants who received the single-focus alcohol risk-reduction intervention drank less frequently and consumed fewer drinks per drinking day as compared with no-intervention control participants, but did not differ from control participants in their frequency of intercourse without a condom or number of sexual partners. Participants who received the single-focus HIV risk-reduction intervention evidenced fewer unprotected sex events during follow-up, as compared with control participants. The number of sexual partners reported during follow-up did not differ by condition. Effects of the interventions did not vary significantly over time and were not moderated by participant gender. Results suggest that intervening to reduce alcohol use may not reduce risky sexual behavior among nonminority college students, but that a brief motivational intervention targeting HIV risk behavior may have utility for reducing the frequency of unprotected sex in this population.     

Phonological similarity effects in simple and complex span tasks

Three experiments were conducted to examine the effect of phonological similarity in simple and complex memory span tasks. In Experiment 1, participants performed either a simple or a complex span task, and the memoranda within lists were either phonologically similar or distinct. Phonologically similar lists consisted of words that rhymed.The simple span task was word span. There were two complex span tasks; one was the original reading span task, and the other was a variant of reading span in which all the sentences within a list were contextually related. The classic phonological similarity decrement was observed in word span. In contrast, phonological similarity facilitation was observed in both versions of reading span. This facilitation effect was further investigated in Experiment 2 using two new versions of reading span. In Experiment 2, the sentences in reading span were either short or long, and the memoranda were presented separately from, and were unrelated to, the sentences. Again, words within phonologically similar lists rhymed, and again, facilitation was observed. In Experiment 3, phonological similarity was operationalized in terms of feature overlap, rather than rhyme. The classic phonological similarity decrement was still observed in word span, but facilitation was not observed in complex span. The results suggest that phonological similarity, when operationalized using words that rhyme, serves as a list retrieval cue and that complex span tasks are more dependent on cue-driven memory retrieval mechanisms than are simple span tasks.     

An introduction to Bayesian hierarchical models with an application in the theory of signal detection

Although many nonlinear models of cognition have been proposed in the past 50 years, there has been little consideration of corresponding statistical techniques for their analysis. In analyses with nonlinear models, unmodeled variability from the selection of items or participants may lead to asymptotically biased estimation. This asymptotic bias, in turn, renders inference problematic. We show, for example, that a signal detection analysis of recognition memory data leads to asymptotic underestimation of sensitivity. To eliminate asymptotic bias, we advocate hierarchical models in which participant variability, item variability, and measurement error are modeled simultaneously. By accounting for multiple sources of variability, hierarchical models yield consistent and accurate estimates of participant and item effects in recognition memory. This article is written in tutorial format; we provide an introduction to Bayesian statistics, hierarchical modeling, and Markov chain Monte Carlo computational techniques.     

The Asian American values scale--multidimensional: development, reliability, and validity

The development of the 42-item Asian American Values Scale-Multidimensional (AAVS-M) is presented. In Study 1, data from 163 Asian American respondents were subjected to a principal components analysis, which reduced the initial set of 180 items to 42 items divided into 5 components: collectivism, conformity to norms, emotional self-control, family recognition through achievement, and humility. The data also revealed initial evidence of the AAVS-M total and subscale scores' reliability and validity. In Study 2, data from 189 Asian American respondents were subjected to a confirmatory factor analysis, which supported a hierarchical factor structure underlying the AAVS-M. Additional reliability and validity evidence of AAVS-M total and subscale scores were found. In Study 3, data from 38 Asian American respondents yielded evidence of AAVS-M total and subscale scores' test-retest reliability.     

The effects of binge MDMA on acquisition and reversal learning in a radial-arm maze task

The current study used the partially-baited radial-arm maze paradigm to study the effects of a single-treatment high-dose exposure ('binge') to MDMA (± 3,4-methylenedioxymethaphemtamine or 'Ecstasy') on memory task acquisition. Sprague-Dawley rats were administered a binge dose (4 × 10 mg/kg) of MDMA and their ability to subsequently acquire the radial-arm maze task was compared against saline controls. The MDMA-treated rats were significantly slower to learn the task and made more reference memory errors than the controls. Working memory function was found to be relatively unimpaired. Following a reversal of task rules the MDMA-treated rats were again significantly slower to acquire the appropriate rule despite having eventually achieved a similar level of overall performance as control rats. However evidence of drug tolerance was found when all rats were challenged with an acute low dose of MDMA (1 × 4.0 mg/kg) because the binge MDMA rats were relatively less impaired. Therefore, although binge treated MDMA rats were able to achieve very accurate performance equivalent to the controls they took significantly longer to do this and were less able to adapt their behavior to a change in task rules. In addition the binge treated MDMA rats displayed tolerance to acute MDMA exposure. These findings are consistent with the possibility that human Ecstasy users may show deficits in acquiring information and may experience deficits in cognitive flexibility as well as developing tolerance to the drug with repeated exposure.     

The completeness of the pragmatic solution to Moore’s paradox in belief: a reply to Chan

Moore’s paradox in belief is the fact that beliefs of the form ‘p and I do not believe that p’ are ‘absurd’ yet possibly true. Writers on the paradox have nearly all taken the absurdity to be a form of irrationality. These include those who give what Timothy Chan calls the ‘pragmatic solution’ to the paradox. This solution turns on the fact that having the Moorean belief falsifies its content. Chan, who also takes the absurdity to be a form of irrationality, objects to this solution by arguing that it is circular and thus incomplete. This is because it must explain why Moorean beliefs are irrational yet, according to Chan, their grammatical third-person transpositions are not, even though the same proposition is believed. But the solution can only explain this asymmetry by relying on a formulation of the ground of the irrationality of Moorean beliefs that presupposes precisely such asymmetry. I reply that it is neither necessary nor sufficient for the irrationality that the contents of Moorean beliefs be restricted to the grammatical first-person. What has to be explained is rather that such grammatical non-first-person transpositions sometimes, but not always, result in the disappearance of irrationality. Describing this phenomenon requires the grammatical first-person/non-first person distinction. The pragmatic solution explains the phenomenon once it is formulated in de se terms. But the grammatical first-person/non-first-person distinction is independent of, and a fortiori, different from, the de se/non-de se distinction presupposed by pragmatic solution, although both involve the first person broadly construed. Therefore the pragmatic solution is not circular. Building on the work of Green and Williams I also distinguish between the irrationality of Moorean beliefs and their absurdity. I argue that while all irrational Moorean beliefs are absurd, some Moorean beliefs are absurd but not irrational. I explain this absurdity in a way that is not circular either.