Expert face coding: Configural and component coding of own-race and other-race faces

Configural and holistic coding are hallmarks of face perception. Although recent studies have shown that own-race faces are coded more holistically than other-race faces, the evidence for better configural coding of own-race faces is equivocal. We directly measured configural and component coding of own- and other-race male faces in Caucasian and Chinese participants. We manipulated individual features (components) or their spatial relations (configurations) using a novel morphing method to vary difficulty parametrically and tested sensitivity to these changes in a sequential matching task. Both configural and component coding were better for upright own-race than for upright other-race faces. Inversion impaired detection of configural changes more than it did detection of component changes, but also impaired performance more for easier discriminations,independent of type of change. These results challenge explanations of face expertise that rely solely on configural and holistic processing, and also call into question the widespread interpretation of large inversion decrements as diagnostic of configural coding.     

Remembering plurals: Unit of coding and form of coding during serial recall

Subjects were required to recall lists of six words which had been presented visually in sequence. One or two of the words might be plural nouns. A substantial number of errors occurred in which the plural form became detached from its original root. This is taken as evidence for a morpheme-based code as opposed to a unitary word code. A significantly high proportion of these errors maintained the form of the plural ( /S/, /Z/ or (ЪZ/) which is considered evidence for a primarily phonological coding of the plural morpheme. There is however a suggestion that on some occasions the plural is coded morphemically—i.e., in a way which does not distinguish between the various plural endings.     

Color coding information: assessing alternative coding systems using independent brightness and hue dimensions

Can independent dimensions of brightness and hue be used in a combined digital information code? This issue was addressed by developing 2 color-coding systems and testing them on informed and naive participants in signal beam detection and classification experiments for simulated sonar displays. Each coding system's results showed both groups efficiently used encoded information that varied simultaneously along the 2 dimensions of brightness and hue. Findings support the proposed procedures for developing color information codes and the validity of such information codes across different populations. Applied significance of these results is provided by the test of principled methods of color-code construction and the demonstration that extending the information content of user interfaces beyond 1 dimension is feasible in practice.     

Linear and nonlinear opponent color coding

The linearity axiom as proposed by Krantz (1975) is confirmed for red/green equilibria, i.e., lights which appear neither reddish nor greenish (unique yellows, unique blues, and achromatic colors). This experiment also gave some evidence of “veiling,” i.e., the masking of a weak hue component by a strong one. In a second experiment, hue magnitude estimates (HME) for the green component were obtained in variable mixtures of unique green and unique yellow stimuli. Contrary to the suggestion raised by the work of Yager and Taylor (1970), we did not find the relation between the HME and the luminance of the green stimulus to be independent of the amount of added yellow. A relation proposed by Indow and Stevens (1966), in which the proportion of the green luminance is taken as the relevant psychophysical unit, gives a better fit to our data. It is shown, however, that alternative interpretations of such data are possible and that this type of experiment cannot be conclusive regarding the issue of the possibility of absolute judgment of opponent hue attributes.

     

Ensemble coding of faces occurs in children and develops dissociably from coding of individual faces

Ensemble coding allows adults to access useful information about average properties of groups, sometimes even in the absence of detailed representations of individual group members. This form of coding may emerge early in development with initial reports of ensemble coding for simple properties (size, numerosity) in young children and even infants. Here we demonstrate that ensemble coding of faces, which provides information about average properties of social groups, is already present in 6–8‐year‐old children. This access to average information increases with age from 6 to 18 years and its development is dissociable from age‐related improvements in the coding of individual face identities. This dissociation provides the first direct evidence that distinct processes underlie ensemble and individual coding of face identity, evidence that has been lacking from adult studies. More generally, our results add to the emerging evidence for impressively mature sensitivity to statistical properties of the visual environment in children. They indicate that children have access to gist information about social groups that may facilitate adaptive social behaviour.     

Facial expression coding in children and adolescents with autism: Reduced adaptability but intact norm-based coding

Individuals with autism spectrum disorder (ASD) can have difficulty recognizing emotional expressions. Here, we asked whether the underlying perceptual coding of expression is disrupted. Typical individuals code expression relative to a perceptual (average) norm that is continuously updated by experience. This adaptability of face-coding mechanisms has been linked to performance on various face tasks. We used an adaptation aftereffect paradigm to characterize expression coding in children and adolescents with autism. We asked whether face expression coding is less adaptable in autism and whether there is any fundamental disruption of norm-based coding. If expression coding is norm-based, then the face aftereffects should increase with adaptor expression strength (distance from the average expression). We observed this pattern in both autistic and typically developing participants, suggesting that norm-based coding is fundamentally intact in autism. Critically, however, expression aftereffects were reduced in the autism group, indicating that expression-coding mechanisms are less readily tuned by experience. Reduced adaptability has also been reported for coding of face identity and gaze direction. Thus, there appears to be a pervasive lack of adaptability in face-coding mechanisms in autism, which could contribute to face processing and broader social difficulties in the disorder.     

Location coding in chess

Whether the chunks used in memorizing chess positions are general and relatively encoded schemata or very precisely coded instances is a problem that has raised some controversy within the psychology of chess skill. As chess research has had a strong impact on expertise research, this problem is important in many areas of skills research other than chess. To resolve it, four experiments were set up. In the experiments it was shown that subjects were better at recalling correctly located non-transposed chunks than transposed chunks, which were similar in structure but incorrectly located on the chessboard. The results imply that the representation of chess-specific patterns in the memory of a chess player contains not only information about the forms of chess-specific patterns, but also about their absolute locations on the chessboard. This provides an explanation for the well-known interaction between skill and type of position and its disappearance in recent experiments by Lories and Saariluoma. It can be argued that the difficulty of recalling random positions is not chiefly caused by the total absence of chunks but by their dislocation.     

Age, exercise, and coding performance

We investigated the effects of exercise on the coding performance of young and older subjects. Hypotheses were tested that exercise either facilitates spatial localization or reduces susceptibility to distraction in older subjects. In a balanced design, we administered Digit Symbol and Symbol Digit coding tasks to exercisers and nonexercisers at two age levels under conditions of low or high within-task interference. The findings showed higher performance by the exercisers than by the nonexercisers only at the older age level and only with the Symbol Digit task. These findings support the hypothesis that exercise compensates for a loss of spatial localization skills with age. We found no evidence that susceptibility to distraction either increased with age or was affected by chronic exercise.     

Categorical shape and color coding by pigeons

Categorical coding is the tendency to respond similarly to discriminated stimuli. Past research indicates that pigeons can categorize colors according to at least three spectral regions. Two present experiments assessed the categorical coding of shapes and the existence of a higher order color category (all colors). Pigeons were trained on two independent tasks (matching-to-sample, and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials one of the two comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the two stimuli from the other task was introduced suggested categorical coding rules. In Experiment 1 evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Experiment 2 replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Overall, the results indicate that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical.     

Acoustic and associative coding in short-term memory

Short lists of word-digit pairs were presented to 456 college student subjects. One of the words was repeated as a memory probe either immediately after list presentation or after a short rehearsal interval. The stimulus words were either acoustically identical or associatively related (UP, DOWN). Both acoustic identity and associative relatedness produced a memory decrement which decreased with rehearsal. One interpretation of these results is that the primary memory trace is a multiple-dimension one and that, given time, subjects can recover non-acoustic information from it. The data also indicate that the “fate” over time is different for acoustically similar and associatively related items.     

Visual and name coding in dyslexic children

Summary Four experiments are reported which were designed to test for differences between dyslexic and non-dyslexic subjects at a number of visual information processing functions. It is argued that the older dyslexic child's reading problems cannot be ascribed to slowness of visual code production, to the limited capacity of the system, or to an extra rapid rate of decay. The results are compatible with the theory that, as a group, the dyslexic children tested show a slowness or inadequacy at a non-visual, name or linguistic coding level. It is suggested that this deficiency does not lie in the area of articulatory encoding but at an earlier stage where phonological or lexical codes are produced from visual stimuli.     

Orientation of stimuli and binocular disparity coding

An experiment is described which attempts to relate physiological work on disparity coding in the cat to a psychophysical situation using human subjects and Julesz stereograms composed of small line elements. It was found that depth perception occurred only if matching disparate lines in each stereogram shared a similar orientation. Depth began to deteriorate if an orientation difference exceeded 10° and it was extinguished at about 60°. The results are interpreted as supporting the hypothesis that shape-sensitive disparity detectors of the kind found in the cat exist also in man.     

An analogy between colour and spatial coding

The early stages of colour coding are well established in that the trichromatic receptor stage is followed by a set of opponent colour channels. One interpretation of the sequence is that opponent channels carry unrelated aspects of the colour stimulus, unlike the cone channels. The overlap of the cone channels can be removed by decorrelating their spectral-sensitivity functions, and this procedure has been found to give opponent colour channels which match those found psychophysically. Since the known spatial-frequency channels also show considerable overlap, the question arises which aspects of the spatial stimulus are captured by decorrelating the spatial-frequency channels. The results of decorrelating the spatial-frequency channels are that the first decorrelated spatial filter acts as a broad bandpass filter which has a peak sensitivity at 7.9 cycles deg-1, and that the second decorrelated spatial filter acts as an opponent spatial-frequency channel, with a minimum output at a low (4.1 cycles deg-1) spatial frequency and a maximum output at a high (15.1 cycles deg-1) spatial frequency. The characteristics of the first decorrelated filter closely resemble the properties of the foveal perceptive field which have been used to explain the Hermann grid illusion. Thus, the decorrelation analysis produces a model for the functional organisation of the channel implementation at the neural and psychophysical levels, but which directly relates to the subjective appearance of the visual stimuli.     

Phonological coding in rhyming and homophony judgement

Recent data concerning the effects of articulatory suppression on the time taken to decide whether pairs of letter strings rhyme or sound the same are inconsistent. A consideration of the nature of the two tasks, as well as independent experimental evidence, suggests that they have different processing requirements. Two experiments are reported. Experiment 1 shows that articulatory suppression increases rhyming judgement time for both words and non-words. Experiment 2 shows that suppression does not increase homophony judgement time for either words or non-words. It is suggested that only rhyming judgements require the registration of a post-lexical representation in the articulatory loop component of working memory. This process of registration is hindered when subvocalization is prevented by articulatory suppression.     

Spatial coding and oblique discrimination by children

Children from five to eight years of age learned to discriminate between mirrorimage oblique lines more readily when cards bearing the obliques were presented vertically than when they were presented horizontally. The difference in performance between the vertical and horizontal planes could not be accounted for by differences in either the external visual context or the availability of asymmetrical body information (e.g., left vs right hand). The superiority of the vertical plane was attributed to the congruence of objective, bodily, and retinal vertical axes for the vertical, but not the horizontal plane, It was concluded, on this basis, that at least part of children's difficulty discriminating between mirror-image obliques is due to their difficulty establishing the internalized vertical axis necessary for the left-right spatial coding of the obliques.     

Temporal structure coding with and without awareness

In order to interpret a constantly changing environment, visual events far apart in space and time must be integrated into a unified percept. While spatial properties of invisible signals are known to be encoded without awareness, the fate of temporal properties remains largely unknown. Here, we probed temporal integration for two distinct motion stimuli that were either visible or rendered invisible using continuous flash suppression. We found that when invisible, both the direction of apparent motion and the gender of point-light walkers were processed only when defined across short time periods (i.e., respectively 100 ms and 1000 ms). This limitation was not observed under full visibility. These similar findings at two different hierarchical levels of processing suggest that temporal integration windows shrink in the absence of perceptual awareness. We discuss this phenomenon as a key prediction of the global neuronal workspace and the information integration theories of consciousness.     

Eye movements and spatial coding in reading

Summary Two experiments are reported which test the hypothesis that during reading subjects maintain in working memory a record of the spatial location of items and that this code is used to guide reinspections. In the first experiment the premisses of short syllogisms were read, one word at a time, under three presentation conditions: (a) in correct temporal order and in appropriate sequential spatial locations; (b) in correct temporal order but in random spatial locations; (c) in correct temporal order and in a single central location. A measure was taken of the time to respond to possible conclusions of the syllogisms. Solution times were longer in conditions (b) and (c) relative to (a). In the second experiment eye movements were recorded as subjects judged the soundness of auditorily presented conclusions following visual presentation of the premisses of syllogisms. Non-random eye movements took place during the solution phase directed to locations previously occupied by text in the display.