Inducing synesthesia in non-synesthetes: Short-term visual deprivation facilitates auditory-evoked visual percepts

Sounds can modulate activity in visual cortex, facilitating the detection of visual targets. However, these sound-driven modulations are not thought to evoke conscious visual percepts in the general population. In individuals with synesthesia, however, multisensory interactions do lead to qualitatively different experiences such as sounds evoking flashes of light. Why, if multisensory interactions are present in all individuals, do only synesthetes experience abnormal qualia? Competing models differ in the time required for synesthetic experiences to emerge. The cross-activation model suggests synesthesia arises over months or years from the development of abnormal neural connections. Here we demonstrate that after ∼5 min of visual deprivation, sounds can evoke synesthesia-like percepts (vivid colors and Klüver form-constants) in ∼50% of non-synesthetes. These results challenge aspects of the cross-activation model and suggest that synesthesia exists as a latent feature in all individuals, manifesting when the balance of activity across the senses has been altered.     

The locus of spatial attention during the temporal integration of visual memories and visual percepts

Temporal integration is a process by which two serially presented visual stimuli are mentally integrated to form a composite representation. In the present research, we explored how spatial selective attention is used during the delay separating stimuli, in order to determine the contents of spatial working memory in this task. A two-task situation was created. On the primary task, two dot arrays were serially presented within a grid, leaving one space empty, which subjects identified. On the secondary task, instead of the second array, a discrimination probe was presented. Integration accuracy increased through delays of 1,500 msec, revealing an estimate of the time required to form an optimal memory trace for integration. Once the memory trace was formed (but not before), response time to the probe was faster if it was presented in a location previously occupied by a dot from Array 1. This indicates that during the delay separating the arrays, the subjects assigned spatial attention to the locations occupied by the first array and actively maintained the leading array in working memory. Implications for theories of visual processing and memory are discussed.     

Reexamining the word length effect in visual word recognition: New evidence from the English Lexicon Project

In the present study, we reexamined the effect of word length (number of letters in a word) on lexical decision. Using the English Lexicon Project, which is based on a large data set of over 40,481 words (Balota et al., 2002), we performed simultaneous multiple regression analyses on a selection of 33,006 English words (ranging from 3 to 13 letters in length). Our analyses revealed an unexpected pattern of results taking the form of a U-shaped curve. The effect of number of letters was facilitatory for words of 3–5 letters, null for words of 5–8 letters, and inhibitory for words of 8–13 letters. We also showed that printed frequency, number of syllables, and number of orthographic neighbors all made independent contributions. The length effects were replicated in a new analysis of a subset of 3,833 monomorphemic nouns (ranging from 3 to 10 letters), and also in another analysis based on 12,987 bisyllabic items (ranging from 3 to 9 letters). These effects were independent of printed frequency, number of syllables, and number of orthographic neighbors. Furthermore, we also observed robust linear inhibitory effects of number of syllables. Implications for models of visual word recognition are discussed.     

On the relations between crowding and visual masking

To study the question of which processes contribute to crowding and whether these are comparable to those of visual temporal masking, we varied the stimulus onset asynchrony (SOA) between target and flankers in a crowding setting. Monotonically increasing Type A masking functions observedfor small spacings and large eccentricities indicate that the integration of information from target and flankers underlies crowding. Decreasing masking functions obtained for large spacings and small eccentricities relate processes of crowding to those contributing to Type B masking. In addition, Type B masking was more frequent with letter-like nonletter flankers than with letter flankers, suggesting that Type B masking, just like crowding over large areas, is due to higher level interactions. The rapid decrease of the effects of interletter spacing and eccentricity with increasing SOA indicates that positional information is transient.     

Long-term memory for elementary visual percepts: memory psychophysics of context and acquisition effects

In the first phase of each of two experiments, participants learned to associate a set of labels (i.e., consonant-vowel-consonant [CVC]) with a set of line lengths by using a paired-associate learning procedure. In the second phase of each experiment, these learned labels were used as memorial standards in the method of constant stimuli. Psychometric functions and the associated indices of discriminative performance (i.e., Weber fractions [WFs], just noticeable difference, and point of subjective equality) were then obtained for the remembered standards. In Experiment 1, WFs (i.e., the indices of memory precision) obtained with remembered standards were found to be higher (i.e., had poorer discriminability) than were WFs obtained with perceptual standards. In addition, WFs obtained with the remembered standards exhibited serial position effects (i.e., poorer discriminability for central items in the memory ensemble) and systematically varied with set size (i.e., the number of standards in the memory set), but WFs obtained with perceptual standards did not depend on serial position or set size. In Experiment 2, increasing the number of acquisition trials reduced WFs and diminished serial position effects. In addition, WFs did not vary systematically with the "physical" spacing between the standards in memory, but they did with the ordinal spacing. The results are consistent with a noisy analogue representation of remembered magnitudes, whereby central items in a memory ensemble are subject to lateral inhibition and thus reduced discriminability. Finally, presentation order effects, as defined by the classic time-order error, were observed with purely perceptual comparisons but not with comparisons involving a remembered standard. This latter finding is inconsistent with a strong form of the functional equivalence view of perception and memory.     

Flicker-light induced visual phenomena: frequency dependence and specificity of whole percepts and percept features

Flickering light induces visual hallucinations in human observers. Despite a long history of the phenomenon, little is known about the dependence of flicker-induced subjective impressions on the flicker frequency. We investigate this question using Ganzfeld stimulation and an experimental paradigm combining a continuous frequency scan (1–50 Hz) with a focus on re-occurring, whole percepts. On the single-subject level, we find a high degree of frequency stability of percepts. To generalize across subjects, we apply two rating systems, (1) a set of complex percept classes derived from subjects’ reports and (2) an enumeration of elementary percept features, and determine distributions of occurrences over flicker frequency. We observe a stronger frequency specificity for complex percept classes than elementary percept features. Comparing the similarity relations among percept categories to those among frequency profiles, we observe that though percepts are preferentially induced by particular frequencies, the frequency does not unambiguously determine the experienced percept.     

Intentional control of visual processing benefits from referential objects

Arguments have been made that enhanced visual processing occurs in the area of the palms of the hands due to greater density of bimodal neurons. An alternative is that the hands serve as reference objects relative to which attentional resources are allocated. Two experiments were conducted to determine whether the palms are unique in speeding responses in an Eriksen flanker-type task compared with other parts of the hands and objects used as barriers. In Experiment 1, the hands were crossed and positioned so that the palms faced outward toward letters located in the outer positions. Trial blocks differed in whether the centrally located letter or outer letters were designated as the target for responding. Results yielded reductions in flanker interference much as obtained when the palms face inward. This reduction occurred regardless of whether the center or outer positions of the letters were designated as the target. Experiment 2 replicated these results using as reference objects wooden blocks that mimicked the hands' physical contours, positioned with a curve-edge facing outwards. The results lend support to the referential coding account of the reduction of flanker interference.     

Underlying processes in the implicit association test: dissociating salience from associations

The authors investigated whether effects of the Implicit Association Test (IAT) are influenced by salience asymmetries, independent of associations. Two series of experiments analyzed unique effects of salience by using nonassociated, neutral categories that differed in salience. In a 3rd series, salience asymmetries were manipulated experimentally while holding associations between categories constant. In a 4th series, valent associations of the target categories were manipulated experimentally while holding salience asymmetries constant. Throughout, IAT effects were found to depend on salience asymmetries. Additionally, salience asymmetries between categories were assessed directly with a visual search task to provide an independent criterion of salience asymmetries. Salience asymmetries corresponded to IAT effects and also accounted for common variance in IAT effects and explicit measures of attitudes or the self-concept.     

Overcoming modern-postmodern dichotomies: Some possible benefits for the counselling profession

The rhetorical/discursive turn, in its multiple disciplinary masks, is here to stay. Even psychology is giving in to its charm. The Sophists can smile again, the agora is back and the solipsistic self is in retreat. Dialogical, narrative and cultural psychologies, as well as the counselling profession, triumph the return of the social, the contextual, and the historical to the conceptual realm of the autonomous individual. Though we encourage and enjoy critical views of modern perspectives, such as that supported by poststructuralist and postmodern perspectives, we wonder whether orthodoxies might not be more inclined towards relocation than to eviction. Based on our conviction that a positivist/relativist dichotomy is a poor exchange for older modern dichotomies (self/other), the paper critically reviews the poststructuralist turn in therapy and counselling, and discusses the implications for counselling theory and counsellors' work.     

Aging and autobiographical memory: dissociating episodic from semantic retrieval

Cognitive aging research documents reduced access to contextually specific episodic details inolder adults, whereas access to semantic or other nonepisodic information is preserved or facilitated. The present study extended this finding to autobiographical memory by using a new measure; the Autobiographical Interview. Younger and older adults recalled events from 5 life periods. Protocols were scored according to a reliable system for categorizing episodic and nonepisodic information. Whereas younger adults were biased toward episodic details reflecting happenings, locations, perceptions, and thoughts, older adults favored semantic details not connected to a particular time and place. This pattern persisted after additional structured probing for contextual details. The Autobiographical Interview is a useful instrument for quantifying episodic and semantic contributions to personal remote memory.     

Haptic orientation perception benefits from visual experience: evidence from early-blind, late-blind, and sighted people

Early-blind, late-blind, and blindfolded sighted participants were presented with two haptic allocentric spatial tasks: a parallel-setting task, in an immediate and a 10-sec delay condition, and a task in which the orientation of a single bar was judged verbally. With respect to deviation size, the data suggest that mental visual processing filled a beneficial role in both tasks. In the parallel-setting task, the early blind performed more variably and showed no improvement with delay, whereas the late blind did improve, but less than the sighted did. In the verbal judgment task, both early- and late-blind participants displayed larger deviations than the sighted controls. Differences between the groups were absent or much weaker with respect to the haptic oblique effect, a finding that reinforces the view that this effect is not of visual origin. The role of visual processing mechanisms and visual experience in haptic spatial tasks is discussed.     

Reversal of object-based benefits in visual attention

In divided-attention tasks, observers must make speeded (or near threshold accuracy) judgements concerning two target features in a display. Typically, when the two features belong to the same object they are more rapidly judged than when they belong to separate objects, a pattern of findings referred to here as a “same-object benefit”. However, we note here that many of these studies share common features, in particular the use of pre-exposed, outline, and/or overlapping objects, and their findings may not generalize to other types of display. Building substantially on previous work by Davis, Welch, Holmes, and Shepherd (2001), we show in four new studies that once these features are not present in a divided-attention task, no same-object benefits are reported. Rather we now find “same-object costs”, where features belonging to a single object are less rapidly judged than features belonging to separate objects.     

On the benefits of transient attention across the visual field

There are well-known differences in resolution and performance across the visual field with performance generally better for the lower than the upper visual hemifield. Here we attempted to assess how transient attention summoned by a peripheral precue affects performance across the visual field. Four different attentional precueing tasks were used, varying in difficulty and attentional load. When a single discrimination target was presented (experiments 1 and 2), precues that summon transient attention had very little, if any, effect upon performance. However, when the target was presented among distractors (experiments 3 and 4), the precue had a substantial effect upon discrimination performance. The results showed that asymmetries in visual resolution between the upper and lower hemifields become more pronounced with increasing eccentricity. Furthermore, when the observers performed a precued acuity task with distractors, involving the judgment of the relative position of a small disk within a larger one, there was an asymmetry in the transient attentional effect on discrimination performance; the benefits of transient attention were larger in the upper than in the lower hemifield. Areas in the visual field where visual performance is generally worse thus appear to receive the largest attentional boost when needed. Possible ecological explanations for this are discussed.     

The representation of simple ensemble visual features outside the focus of attention

The representation of visual information inside the focus of attention is more precise than the representation of information outside the focus of attention. We found that the visual system can compensate for the cost of withdrawing attention by pooling noisy local features and computing summary statistics. The location of an individual object is a local feature, whereas the center of mass of several objects (centroid) is a summary feature representing the mean object location. Three experiments showed that withdrawing attention degraded the representation of individual positions more than the representation of the centroid. It appears that information outside the focus of attention can be represented at an abstract level that lacks local detail, but nevertheless carries a precise statistical summary of the scene. The term ensemble features refers to a broad class of statistical summary features that we propose collectively make up the representation of information outside the focus of attention.     

Sequential resolution of fragmented visual percepts: experimental investigation of a subject's perceptual experience after a right medial temporal stroke

This report concerns the fragmented visual percepts in a woman, TR, following a right entorhinal-perirhinal infarct. In a previous report, Weddell [Weddell, R. A. (2005). A visual disorder producing highly selective deletion of recurring letters. Cortex, 41, 471-485] linked TR's highly selective tendency to delete recurrent letters with her fragmented percepts. The conflation of same-identity form elements was attributed to anterior extrastriate damage, which reduced the amount of information sustainable in fully resolved visual percepts, and the present experimental investigation of her subjective account of segment formation and resolution completes the story. She said that complex objects and long words first appeared as blurred regions, which sometimes included form elements. It is argued that figure-centred attentional mechanisms subdivided this blurred region into up to 3-4 parts. String length, lexical status (word vs. nonword), and background colour and/or luminance determined fragment length. Two rules described the fragment resolution sequence: largest segments usually resolved first, left-to-right resolution accounting for a few sequences. This resolution sequence occurred when stimuli were exposed too briefly for saccadic exploration, implicating endogenous attentional shifts. Experiment 4 confirmed TR's assertion that spatial, orthographic, and phonological information were stored during the fragment resolution process. Moreover, TR exerted considerable voluntarily control over the fragment resolution sequence and some influence over fragment length. Finally, these findings were interpreted in terms of an extended version of a neural network model of vision largely derived from nonhuman primate studies.     

Reexamining the Calculus of Voting

This study applies social cognitive theory to the study of voter turnout, examining the effects of self‐efficacy on citizens' decisions of whether or not to vote. Consistent with recent arguments in cognitive psychology ( Fenton‐O'Creevy, Nicholson, Soane, & Willman, 2003, 2005 ), I argue that excessive perceptions of self‐efficacy lead some citizens to overestimate their vote's impact in close elections and to vote as a consequence of these perceptions. This illusion of control is further engendered by the features of skill‐based activities such as choice, personal involvement, stimulus familiarity, and exertion of effort ( Langer, 1975 ) that are inherent in the act of voting. Employing both cross‐sectional and panel data, I find that individuals with high levels of self‐efficacy are more likely to be moved to vote by perceptions that an election will be close than are citizens with low levels of self‐efficacy.     

Visual consciousness: dissociating the neural correlates of perceptual transitions from sustained perception with fMRI

To investigate the possible dichotomy between the neurophysiological bases of perceptual transitions versus sustaining a particular percept over time, an fMRI study was conducted with subjects viewing fragmented pictures. Unlike most other perceptually unstable stimuli, fragmented pictures give rise to only one perceptual transition and a continuous period of sustained perception. Earlier research is inconclusive on the subject of which anatomical regions should be attributed to what temporal aspect of perception, and the aim of the present study was to shed more light on the subject. In this study occipitotemporal and fronto-parietal regions were found to be activated for both aspects. However, regions in the medial-temporal lobe were activated specifically for transitions, whereas medial and dorsolateral prefrontal regions were activated specifically for sustained perception. These results provide further support for the theory that the initial creation of perceptual awareness and upholding perceptual awareness over time are separate processes involving different brain regions.     

Relating the perception of visual ensemble statistics to individual levels of autistic traits

Integrating information across the visual field into an ensemble (e.g., seeing the forest from the trees) is an effective strategy to efficiently process the visual world, and one that is often impaired in autism spectrum disorder. Individual differences in sensory processing predict ensemble encoding, providing a potential mechanism for differing perceptual strategies across individuals, and possibly across diagnostic groups exhibiting atypical sensory processing. Here, we explore whether ensemble encoding is associated with traits associated with autism spectrum disorder (ASD). Participants (N=68) were presented with an ensemble display consisting of circles of varying sizes and colors, and were asked to remember the size of the red and blue circles, while ignoring the green circles. Participants were then cued to a target location after a brief delay, and instructed to report the remembered size of the circle they had previously viewed in that location, as ensemble information commonly biases memory for individual objects toward the probed mean of a set of similar objects. The Autism-spectrum Quotient (AQ) was completed to measure each individual’s level of autistic traits. We found that an individual’s level of ensemble perception, measured as their bias toward the probed mean, was negatively associated with a higher level of ASD traits. These results suggest that individuals with higher levels of ASD traits are less likely to integrate perceptual information. These findings may shed light on different perceptual processing within the autism spectrum, and provide insight into the relationship between individual differences and ensemble encoding.