Weak Interactions: Asymmetry of Time or Asymmetry in Time?

The paper analyzes the philosophical consequences of the recent discovery of direct violations of the time–reversal symmetry of weak interactions. It shows that although we have here an important case of the time asymmetry of one of the fundamental physical forces which could have had a great impact on the form of our world with an excess of matter over antimatter, this asymmetry cannot be treated as the asymmetry of time itself but rather as an asymmetry of some specific physical process in time. The paper also analyzes the consequences of the new discovery for the general problem of the possible connections between direction (arrow) of time and time-asymmetric laws of nature. These problems are analyzed in the context of Horwich’s Asymmetries in time: problems in the philosophy of science (1987) argumentation, trying to show that existence of a time–asymmetric law of nature is a sufficient condition for time to be anisotropic. Instead of Horwich’s sufficient condition for anisotropy of time, it is stressed that for a theory of asymmetry of time to be acceptable it should explain all fundamental time asymmetries: the asymmetry of traces, the asymmetry of causation (which holds although the electrodynamic, strong and gravitational interactions are invariant under time reversal), and the asymmetry between the fixed past and open future. It is so because the problem of the direction of time has originated from our attempts to understand these asymmetries and every plausible theory of the direction of time should explain them.     

Attenuated hypothesis or attenuated test of hypothesis?

After discussing several of the criticisms made by Professor Jensen, it is concluded that the Spearman hypothesis, as currently worded, has been disconfirmed. The near-zero correlation between blacks and low socio-economic status (SES) whites is not an artifact of the methodology. Neither is it a sampling fluke. The logic of sampling error does not apply to the arbitrary selection of intercorrelated tests from an undefined population. It is important also that low and high SES white differences are highly correlate with general factor loadings in a very heterogeneous selection of tests. Research attention should be turned to the difference in outcome of the race and SES comparisons.     

Re-examining selective adaptation: Fatiguing feature detectors,or distributional learning?

When a listener hears many good examples of a /b/ in a row, they are less likely to classify other sounds on, e.g., a /b/-to-/d/ continuum as /b/. This phenomenon is known as selective adaptation and is a well-studied property of speech perception. Traditionally, selective adaptation is seen as a mechanistic property of the speech perception system, and attributed to fatigue in acoustic-phonetic feature detectors. However, recent developments in our understanding of non-linguistic sensory adaptation and higher-level adaptive plasticity in speech perception and language comprehension suggest that it is time to re-visit the phenomenon of selective adaptation. We argue that selective adaptation is better thought of as a computational property of the speech perception system. Drawing on a common thread in recent work on both non-linguistic sensory adaptation and plasticity in language comprehension, we furthermore propose that selective adaptation can be seen as a consequence of distributional learning across multiple levels of representation. This proposal opens up new questions for research on selective adaptation itself, and also suggests that selective adaptation can be an important bridge between work on adaptation in low-level sensory systems and the complicated plasticity of the adult language comprehension system.     

Sad people avoid the eyes or happy people focus on the eyes? Mood induction affects facial feature discrimination

Depressed people tend to avoid eye-contact in social situations and in experimental settings, whereas happy people actively seek eye-contact. We report an experiment in which participants made discriminations between faces that had either configural or featural changes made to the eyes, nose, or head shape. The results showed participants induced to be happy detected changes in eyes more often than participants induced to be sad, but failed to detect changes in other facial features. Sad-induced participants detected changes to the head shape but not the eyes. The results are interpreted in terms of differential use of features attended to by happy and sad participants, whereby happy people are more likely to attend to eyes during face perception than sad people.     

The proportion valid effect in covert orienting: Strategic control or implicit learning?

It is well known that the difference in performance between valid and invalid trials in the covert orienting paradigm (i.e., the cueing effect) increases as the proportion of valid trials increases. This proportion valid effect is widely assumed to reflect “strategic” control over the distribution of attention. In the present experiments we determine if this effect results from an explicit strategy or implicit learning by probing participant’s awareness of the proportion of valid trials. Results support the idea that the proportion valid effect in the covert orienting paradigm reflects implicit learning not an explicit strategy.     

Movements or targets: What makes an action in action–effect learning?

According to ideomotor theory, actions become linked to the sensory feedback they contingently produce, so that anticipating the feedback automatically evokes the action it typically results from. Numerous recent studies have provided evidence in favour of such action–effect learning but left an important issue unresolved. It remains unspecified to what extent action–effect learning is based on associating effect-representations to representations of the performed movements or to representations of the targets at which the behaviour aimed at. Two experiments were designed to clarify this issue. In an acquisition phase, participants learned the contingency between key presses and effect tones. In a following test phase, key–effect and movement–effect relations were orthogonally assessed by changing the hand–key mapping for one half of the participants. Experiment 1 showed precedence for target–effect over movement–effect learning in a forced-choice RT task. In Experiment 2, target–effect learning was also shown to influence the outcome of response selection in a free-choice task. Altogether, the data indicate that both movement–effect and target–effect associations contribute to the formation of action–effect linkages—provided that movements and targets are likewise contingently related to the effects.     

Transfer in discrimination learning: Do children mediate more than adults?

A series of four-dimensional, discrimination-learning problems were presented to second-, sixth-, eighth-, and twelfth-grade students (ages 7, 11, 13, and 17 years, respectively). One pretraining problem, using different dimensions, preceded the four experimental problems; these employed identical dimensions and stimulus values. Solutions were selected without dimensional replacement.Blank-trial probes enabled detection of initial predictions. Results clearly indicated that (1) older subjects made dramatically fewer intradimensional predictions (utilizing the solution dimension from the preceding problem) than did younger subjects, (2) all age groups demonstrated systematic changes over problems; these reflected the specific solution sequence experienced, and (3) there were consistent developmental differences in the speed with which subjects noted and utilized regularities across problems.The pattern of data is not congruent with the expectations of mediation theory. However, it is in accord with the transfer hypothesis, which is a recent extension of hypothesis theory. The transfer hypothesis provides a theoretical framework which suggests when we should observe “mediational” behavior (i.e., intradimensional transfer) and when to expect the inverse.     

Quantity discrimination in Tenebrio molitor: evidence of numerosity discrimination in an invertebrate?

Numerosity discrimination, the ability to distinguish between sets with more and less items, is recognised as the foundation for higher numerical abilities. Understanding numerosity discrimination from a comparative perspective is hence pivotal in tracing the evolution of numerical representation systems. However, numerosity discrimination has been well studied only in vertebrates, where two innate systems of number representation have been described: an ‘analog magnitude system’ used to discriminate among numerosities by representing them as cardinal magnitudes and a ‘parallel individualisation system’ that allows precise discrimination among small arrays of items (≤4) by representing objects individually. We investigated the existence of quantity discrimination in an insect species (Tenebrio molitor) by using a spontaneous two-choice procedure in which males were exposed to substrates bearing odours from different numbers of females (≤4) in increasing numerosity ratios (1:4, 1:3 and 1:2). We show that males can discriminate sources of odours reflecting 1 versus 4 and 1 versus 3 females, but not 2 versus 4 or 1 versus 2, indicating that T. molitor males exhibit a marked preference for sources reflecting more female donors only when numerosity ratios are below 1:2. We discuss the functional significance of this finding and whether our pattern of results could be best explained by summation of a non-numerical continuous variable or by the existence of a numerosity discrimination mechanism with an operational signature ratio of 1:2.     

Form discrimination: features or invariants?

Does form discrimination rely on feature analysis, as the indirect theory of perception supposes, or on affordances (behavioural meanings specified by invariant patterns), as direct theory states. Subjects were to indicate the position of a target in a perspective rendering of a plane, displayed for 100 msec. in a large screen projection. In one of the conditions the target disrupted the plane, in the other it did not. Although targets of the two conditions shared the same features, the disruptive targets were discriminated more often than the nondisruptive targets. This result supports the direct approach to perception which states that a perceiver discriminates behaviourally relevant patterns rather than geometrical properties.     

Are age differences in consistent-mapping visual search due to feature learning or attention training?

In this experiment, the ability of young and old adults to differentially modify the attention-attraction strength of targets and distractors relative to feature differentiation was examined. Eight young and 8 old subjects were trained for 8,000 trials in conditions that allowed maximal target-distractor strength differentiation, inhibited target-distractor strength differentiation but facilitated feature differentiation, or inhibited both target-distractor strength differentiation and feature differentiation. Age-related performance was assessed between and within conditions during training and with reversal conditions where the roles of targets and distractors were switched. The pattern of data during training and at reversal supports the proposal that age differences in extended-practice visual search are due to differences in the ability to differentially strengthen targets and distractors.     

Less negative=more positive? Social discrimination as avoidance or approach

A motivational approach to ingroup favoritism based on regulatory focus theory (RFT; Higgins, 1997) is introduced. RFT suggests that individual self-regulation is either more concerned with approaching positive events (promotion focus) or with avoiding negative events (prevention focus). It is suggested that if an individual self-categorizes as a group member, resource allocations to one’s group will be based on these mechanisms of self-regulation. Thus, a promotion focus should engender ingroup favoritism during the distribution of positive resources but not during the distribution of negative resources, whereas a prevention focus should engender ingroup favoritism for negative but not for positive resources. The results of two studies support this prediction based on momentary and chronic regulatory focus. The self-regulation approach to ingroup favoritism provides an explanation for social discrimination in the distribution of positive and negative resources.     

Switching or sharing in dual-task line-length discrimination?

In two experiments, we tested whether subjects switched or shared attention between two simultaneously relevant line-length discrimination tasks. Switching models that allowed within- as well as between-trial switching were considered. In the first experiment, stimulus duration was varied randomly from trial to trial. With varied durations, many switching models predict negative contingencies: for a given duration and attentional allocation, accurate responses on one task should be associated with inaccurate responses on the other task. The results, however, showed no negative contingencies, which is consistent with sharing models. In the second experiment, stimulus duration was reduced to 20 msec, yet responses were more than 75% correct overall. This implies that information was obtained about both of the tasks within single trials, contradicting those switching models which predict that information can be obtained from, at most, one task within a period of 20 msec or less. In short, the results of both experiments support sharing models.     

Induction in variants of White's effect: common or separate mechanisms?

In White's display the gray target surrounded more by black than white appears darker than the target of the same physical luminance surrounded more by white than black. Several subsequent studies have shown that this effect occurs only when the luminance of the test regions lies between the minimum and maximum luminance values of the inducing stripes. With targets either lighter or darker than both inducing stripes, the direction of the effect is reversed and the effect is known as the 'inverted' White's effect. Views differ on whether the classical and inverted White's effects are mediated by common or separate underlying mechanisms. We varied the aspect ratio of the test and inducing regions in the classical and inverted White's effects. Consistent with previously reported findings, we found that the direction of the classical effect did not depend on the amount of black or white border in immediate contact with the test patch. On the other hand, perceived lightness in the inverted White's effect was affected by such variations, suggesting that induction in classical and inverted White's configurations is governed by different mechanisms. These results confirm the critical importance of the interaction between luminance and geometric relationships in induced brightness.     

Manual asymmetry in weight discrimination: hand or spatial-field advantage?

Sixty subjects who were either left-handed or right-handed performed one-handed weight discrimination using their left and right hands in the left and right spatial fields. Differential thresholds, for the left and right hands of both left-handed and right-handed subjects, were found to be lower in the spatial field contralateral to the ear which proved superior in a dichotic listening test. It is concluded that manual asymmetry for weight discrimination results primarily from the mapping of sensorimotor events in the spatial fields onto contralateral cerebral cortex, with an advantage in the spatial field contralateral to the nonlanguage cerebral hemisphere.     

Within-category discrimination of musical chords: Perceptual magnet or anchor?

Recent speech research has begun to evaluate the internal structure of categories. In one such study, Kuhl (1991) found that discrimination was poorer for vowel stimuli that were more representative of the category (prototype, or P, set) than it was for less representative stimuli (nonprototype, or NP, set). This finding was interpreted as indicating that a category prototype may function as a “perceptual magnet,” effectively decreasing perceptual distance, and thus discriminability, between stimuli. The present study examines the function of prototypes in a musical category—another natural, but nonspeech category. Paralleling the Kuhl study, representative (P) and less representative (NP) sets of major triad stimuli were constructed, based on equal temperament. Musically experienced subjects rated the stimuli in each set for goodness as a major triad, with the highest rated stimulus serving as a prototype standard for a subsequent discrimination task. Results from the discrimination task demonstrated better performance in the P context than in the NP context. The current nonspeech results indicate that a prototype functions as an anchor rather than a magnet. In addition to providing a natural, nonspeech standard for comparison with speech findings, the results provide some important insights into the nature of musical categories.     

The variability of practice hypothesis in motor learning: does it apply to Alzheimer's disease?

Based on Schmidt's (1975) variability of practice hypothesis, this study examined acquisition and transfer of a gross motor skill, namely tossing, in 58 patients with Alzheimer's disease (AD) and 58 healthy older adults under constant, blocked, and random practice conditions. While healthy older adults were able to learn the tossing task equally well under the three practice conditions, only AD patients receiving constant practice showed significant improvements. Tests of intermediate transfer yielded the expected random practice advantage in healthy controls but not AD patients. None of the practice conditions facilitated intermediate transfer in AD patients; however, constant practice did benefit these impaired individuals on tests of near transfer. These results indicate that the variability of practice hypothesis does not extend to AD patients. As motor learning and transfer were clearly a function of constant practice, future attempts to retrain basic activities of daily living in AD patients should emphasize consistency in training.     

Order of acquisition in learning perceptual categories: A laboratory analogue of the age-of-acquisition effect?

In the age-of-acquisition (AoA) effect, an advantage for recognition and production is found for items learned early in life, as compared with items learned later. In this laboratory analogue, participants learned to categorize novel random checkerboard stimuli. Some stimuli were presented from the onset of training; others were introduced later. At test, when early and late stimuli had equal cumulative frequency, early stimuli were classified significantly more quickly. Because stimuli were randomly assigned to be introduced either early or late, we can conclude that early stimuli were categorized more quickly because of their order of acquisition. This finding suggests that age- or order-of-acquisition effects are a general property of any learning system.     

Prawn-in-a-tube procedure: habituation or associative learning in cuttlefish?

The prawn-in-a-tube procedure (J. B. Messenger, 1973a) has been used almost exclusively to study associative learning in cuttlefish. In two experiments, the authors sought to determine whether the decline in attack responses observed in this procedure was best accounted for by habituation or associative learning. Results of Experiment 1 revealed an asymmetrical stimulus-specificity effect that could be interpreted as either an instance of habituation or of associative learning. Results of Experiment 2 demonstrated that the response decline could not be reversed following the presentation of a dishabituatory stimulus. The combined results of these experiments support the conclusion that the response decline is best viewed as a resulting of associative processes. The authors considered whether the response decline represents extinction or passive avoidance.     

Beyond unusual? Examining the role of attention in the weapon focus effect

The current study examined whether the weapon focus effect could be accounted for in terms of stimulus novelty. Participants viewed a slideshow of a simulated event while attending to a secondary task. In the critical slide, the target was shown holding a threatening object (weapon condition), a novel object (unusual condition) or a neutral object (control condition). Reaction times on the secondary task were impaired in the weapon and unusual conditions. Participants in the weapon condition had poorest recognition scores for the target's appearance when confidence was also taken into account. Results suggest that while both unusual and threatening objects command attention, the significance of a weapon can lead to impaired performance on less immediately informative aspects of a scene such as target appearance. Copyright © 2006 John Wiley & Sons, Ltd.