Terms of the debate on the format and structure of visual memory

Our ability to actively maintain information in visual memory is strikingly limited. There is considerable debate about why this is so. As with many questions in psychology, the debate is framed dichotomously: Is visual working memory limited because it is supported by only a small handful of discrete “slots” into which visual representations are placed, or is it because there is an insufficient supply of a “resource” that is flexibly shared among visual representations? Here, we argue that this dichotomous framing obscures a set of at least eight underlying questions. Separately considering each question reveals a rich hypothesis space that will be useful for building a comprehensive model of visual working memory. The questions regard (1) an upper limit on the number of represented items, (2) the quantization of the memory commodity, (3) the relationship between how many items are stored and how well they are stored, (4) whether the number of stored items completely determines the fidelity of a representation (vs. fidelity being stochastic or variable), (5) the flexibility with which the memory commodity can be assigned or reassigned to items, (6) the format of the memory representation, (7) how working memories are formed, and (8) how memory representations are used to make responses in behavioral tasks. We reframe the debate in terms of these eight underlying questions, placing slot and resource models as poles in a more expansive theoretical space.     

Perceptual hysteresis in the judgment of auditory pitch shift

Perceptual hysteresis can be defined as the enduring influence of the recent past on current perception. Here, hysteresis was investigated in a basic auditory task: pitch comparisons between successive tones. On each trial, listeners were presented with pairs of tones and asked to report the direction of subjective pitch shift, as either “up” or “down.” All tones were complexes known as Shepard tones (Shepard, 1964), which comprise several frequency components at octave multiples of a base frequency. The results showed that perceptual judgments were determined both by stimulus-related factors (the interval ratio between the base frequencies within a pair) and by recent context (the intervals in the two previous trials). When tones were presented in ordered sequences, for which the frequency interval between tones was varied in a progressive manner, strong hysteresis was found. In particular, ambiguous stimuli that led to equal probabilities of “up” and “down” responses within a randomized context were almost fully determined within an ordered context. Moreover, hysteresis did not act on the direction of the reported pitch shift, but rather on the perceptual representation of each tone. Thus, hysteresis could be observed within sequences in which listeners varied between “up” and “down” responses, enabling us to largely rule out confounds related to response bias. The strength of the perceptual hysteresis observed suggests that the ongoing context may have a substantial influence on fundamental aspects of auditory perception, such as how we perceive the changes in pitch between successive sounds.     

Changes in colour and location as cues of generative transmission in perception of causality

Observers viewed modified launching effect displays containing a spatial gap between the final location of the launcher (a black square) and the initial location of the target (a black outline square with a white interior). In some conditions, a set of stationary objects (black outline squares with white interiors) filled the spatial gap, and these objects began changing colour upon contact from the launcher. The colour changes could involve all gap objects turning black, the first gap object turning dark grey and subsequent gap objects turning successively lighter grey, or first gap object turning light grey and subsequent gap objects turning successively darker grey. The colour changes could move from the launcher to the target or from the target to the launcher. The gap objects could also remain unchanged. Participants rated whether the launcher caused subsequent motion of the target and how much force the launcher imparted to the target. The sequence of colour changes, and the sequence of locations in which colour changes occurred, influenced ratings; sequences of colour changes consistent with the idea that influence of the launcher was transmitted across gap objects to the target resulted in higher ratings. Implications for visual perception of causality are discussed.     

Questions of condom use in the Muslim and Catholic response to HIV and AIDS in Nairobi,Kenya

Religious leaders in Roman Catholic and Sunni Muslim communities in Kenya’s capital city of Nairobi are charged with responding in an official capacity to the pressing concerns facing their respective communities both theologically and practically. However, speaking about sexuality from a religious perspective particularly on the use of condoms in AIDS prevention has been rather troublesome topic many leaders and clergy find problematic discussing openly. This paper offers a comparative analysis of Muslim and Catholic views on sexuality by establishing the parameters within which to consider the presence and activity of Catholic and Muslim leaders in Kenya and the holistic, grassroots approach in responding to the AIDS epidemic in Nairobi regarding condom use.     

Rodent ultrasonic vocalizations as biomarkers of future alcohol use: A predictive analytic approach

Excessive alcohol consumption has a vast, negative impact on society. Rodent models have been successful in furthering our understanding of the biological underpinnings that drive alcohol consumption. Rodents emit ultrasonic vocalizations (USVs) that are each composed of several acoustic characteristics (e.g., frequency, duration, bandwidth, power). USVs reflect neurotransmitter activity in the ascending limb of the mesolimbic dopaminergic and cholinergic neurotransmitter systems and serve as noninvasive, real-time biomarkers of dopaminergic and cholinergic neurotransmission in the limbic system. In the present study, we recorded spontaneously emitted USVs from alcohol-naïve Long-Evans (LE) rats and then measured their alcohol intake. We compared the USV acoustic characteristics and alcohol consumption data from these LE rats with previously published data from selectively bred high-alcohol (P and HAD-1) and low-alcohol (NP and LAD-1) drinking lines from studies with the same experimental method. Predictive analytic techniques were applied simultaneously to this combined data set and revealed that (a) USVs emitted by alcohol-naïve rats accurately discriminated among high-alcohol consuming, LE, and low-alcohol consuming rat lines, and (b) future alcohol consumption in these same rat lines was reliably predicted from the USV data collected in an alcohol-naïve state. To our knowledge, this is the first study to show that alcohol consumption is predicted directly from USV profiles of alcohol-naïve rats. Because USV acoustic characteristics are sensitive to underlying neural activity, these findings suggest that baseline differences in mesolimbic cholinergic and dopaminergic tone could determine the propensity for future alcohol consumption in rodents.     

Counter‐intuitive moral judgement following traumatic brain injury

Several neurological patient populations, including traumatic brain injury (TBI), appear to produce an abnormally ‘utilitarian’ pattern of judgements to moral dilemmas; they tend to make judgements that maximize the welfare of the majority, rather than deontological judgements based on the following of moral rules (e.g., do not harm others). However, this patient research has always used extreme dilemmas with highly valued moral rules (e.g., do not kill). Data from healthy participants, however, suggest that when a wider range of dilemmas are employed, involving less valued moral rules (e.g., do not lie), moral judgements demonstrate sensitivity to the psychological intuitiveness of the judgements, rather than their deontological or utilitarian content (Kahane et al., Social Cognitive and Affective Neuroscience, 7, 2011, 393). We sought the moral judgements of 30 TBI participants and 30 controls on moral dilemmas where content (utilitarian/deontological) and intuition (intuitive/counter‐intuitive) were measured concurrently. Overall TBI participants made utilitarian judgements in equal proportions to controls; disproportionately favouring utilitarian judgements only when they were counter‐intuitive, and deontological judgements only when they were counter‐intuitive. These results speak against the view that TBI causes a specific utilitarian bias, suggesting instead that moral intuition is broadly disrupted following TBI.     

The roles of order,distance, and interstitial items in temporal visual statistical learning

Humans are adept at learning regularities in a visual environment, even without explicit cues to structure and in the absence of instruction—this has been termed “visual statistical learning” (VSL). The nature of the representations resulting from VSL are still poorly understood. In five experiments, we examined the specificity of temporal VSL representations. In Experiments 1A, 1B, and 2, we compared recognition rates of triplets and all embedded pairs to chance. Robust learning of all structures was evident, and even pairs of non-adjacent items in a sequentially presented triplet (AC extracted from a triplet composed of ABC) were recognized at above-chance levels. In Experiment 3, we asked whether people could recognize rearranged pairs to examine the flexibility of learned representations. Recognition of all possible orders of target triplets and pairs was significantly higher than chance, and there were no differences between canonical orderings and their corresponding randomized orderings, suggesting that learners were not dependent upon originally experienced stimulus orderings to recognize co-occurrence. Experiment 4 demonstrates the essential role of an interstitial item in VSL representations. By comparing the learning of quadruplet sets (e.g., ABCD) and triplet sets (e.g., ABC), we found learning of AC and BD in ABCD (quadruplet) sets were better than the learning of AC in ABC (triplet) sets. This pattern of results might result from the critical role of interstitial items in statistical learning. In short, our work supports the idea of generalized representation in VSL and provides evidence about how this representation is structured.     

An evaluation of a visual–visual successive matching‐to‐sample procedure to establish equivalence classes in adults

Traditionally, behavior analysts have studied stimulus equivalence using a matching‐to‐sample (MTS) preparation. Although researchers have shown the utility of MTS to yield equivalence classes, the procedure requires several prerequisite skills for a learner to accurately respond. Previous research with humans and nonhumans has shown that relational responding can be produced via compound stimulus discrimination and successive matching‐to‐sample (S‐MTS). We conducted four experiments with college students to further evaluate the effectiveness of S‐MTS in the establishment of stimulus relations. S‐MTS trials consisted of the presentation of a single sample stimulus followed by one comparison in a fixed location on a computer screen. Depending upon the sample–comparison relation, participants touched (i.e., go) or did not touch (i.e., no‐go) the comparison stimulus. Following training of the baseline relations (AB/BC), we assessed the emergence of symmetry, transitivity, and equivalence performances (i.e., BA/CB and AC/CA). Results support the utility of the S‐MTS procedure as a possible alternative to traditional MTS. This study has direct implications for participants for whom traditional three‐array MTS procedures may be challenging.     

BETWEEN KNOWING AND BEING: REFLECTIONS ON BEING TAUGHT SCIENCE AND RELIGION BY PROFESSOR CHRISTOPHER SOUTHGATE

It is a joy to be asked to contribute to this commemorative edition of Zygon, in honor of my friend Christopher Southgate. But a narrowly academic article seems not to fit the brief of writing a reflection on Southgate's teaching of science and religion, as one who has witnessed it, gladly, as both student and colleague. What follows, then, is deliberately reflective in tone, with little in the way of academic references apart from occasional links to Southgate's own work—though, I hope, enough of a strand of argument to justify inclusion in these pages. My argument is simply put: Southgate teaches by not teaching, but by drawing out knowledge from students and thereby empowering their growth. He is an exemplar, a kind man committed to the unfolding of understanding, interested too in forming dispositions in his students that will lead to their flourishing as thinkers and as people.     

Collaboration facilitates abstract category learning

We examined the effects of collaboration (dyads vs. individuals) and category structure (coherent vs. incoherent) on learning and transfer. Working in dyads or individually, participants classified examples from either an abstract coherent category, the features of which are not fixed but relate in a meaningful way, or an incoherent category, the features of which do not relate meaningfully. All participants were then tested individually. We hypothesized that dyads would benefit more from classifying the coherent category structure because past work has shown that collaboration is more beneficial for tasks that build on shared prior knowledge and provide opportunities for explanation and abstraction. Results showed that dyads improved more than individuals during the classification task regardless of category coherence, but learning in a dyad improved inference-test performance only for participants who learned coherent categories. Although participants in the coherent categories performed better on a transfer test, there was no effect of collaboration.