Timothy R. Jordan

Presenting words without interior letters : superiority over single letters and influence of postmask boundaries

Five experiments examined the perceptibility of exterior letter combinations of words in brief pattern-postmasked displays.

Central Fixations are Inadequately Controlled by Instructions Alone: Implications for Studying Cerebral Asymmetry

A fundamental concern when using visual presentations to study cerebral asymmetry is to ensure that stimuli are presented with the same degree of retinal eccentricity from a central fixation point in either visual field. However, a widely used procedure intended to control fixation location merely instructs participants to fixate appropriately without any other means of ensuring that central fixations actually occur. We assessed the validity of assuming that instructions alone ensure central fixation by using the traditional R VF advantage for words and either (a) only instructions to fixate centrally, or (b) an eye-tracking device that ensured central fixation on every trial. Experiments 1 and 2 found that when only instructions were given, the vast majority of fixations were not central, and more occurred to the right of centre than to the left. Moreover, the prevalence of non-central fixations was otherwise disguised by the finding that both fixation procedures produced similar R VF advantages in overt performance. The impact of typical non-central fixations on performance was revealed by systematically manipulating fixation location in Experiment 3, where deviations in fixation of only 0.25° from centre had a reliable impact on visual field effects. Implications of these findings for studies of cerebral asymmetry are discussed.

Seeing and hearing rotated faces : Influences of facial orientation on visual and audiovisual speech recognition

It is well-known that facial orientation affects the processing of static facial information, but similar effects on the processing of visual speech have yet to be explored fully. Three experiments are reported in which the effects of facial orientation on visual speech processing were examined using a talking face presented at 8 orientations through 360 degrees. Auditory and visual forms of the syllables /ba/, /bi/, /ga/, /gi/, /ma/, /mi/, /ta/, and /ti/ were used to produce the following speech stimulus types: auditory, visual, congruent audiovisual, and incongruent audiovisual. Facial orientation did not affect identification of visual speed per se or the near-perfect accuracy of auditory speech report with congruent audiovisual speech stimuli. However, facial orientation did affect the accuracy of auditory speech report with incongruent audiovisual speech stimuli. Moreover, the nature of this effect depended on the type of incongruent visual speech used. Implications for the processing of visual and audiovisual speech are discussed.

PERCEIVING EXTERIOR LETTERS OF WORDS: DIFFERENTIAL INFLUENCES OF LETTER-FRAGMENT AND NON-LETTER-FRAGMENT MASKS

Previous research shows letter-fragment masks and non-letter-fragment fields have different effects on performance with briefly presented alphabetic targets. However, popular accounts of these differences ignore mask configuration. Over a series of experiments, configurational effects of letter-fragment (LF) and non-letter-fragment (NLF) masks were compared. When the configuration of LF masks matched word boundaries, performance with exterior letter pairs from words improved, whereas performance with illegal exterior-letter pairs and single letters was unaffected. When the same changes were made to NLF masks, only an overall drop in performance occurred, with no selective effect on target type. Thus, although LF mask configuration selectively affected lexical processing, NLF mask configuration produced substantially different effects, indicating problems with contemporary accounts of masking differences that ignore influences of mask configuration.

Effects of Distance on Visual and Audiovisual Speech Recognition.

Face-to-face conversations in every day life are conducted over a range of distances. However, previous research provides only limited indications of the effects of distance on visual and audiovisual speech recognition. We report an experiment which investigated effects of distance on perception of unimodal visual speech and congruent and incongruent audiovisual speech using a talking face presented at distances of 1, 5, 10, 20, and 30m and auditory, visual, congruent, and incongruent forms of the syllables /ba/, /bi/, /ga/, and /gi/. Identification of unimodal visual speech was unaffected by increasing distance to 10m, but was impaired at 20 and 30m. However, despite these drops in unimodal visual speech identification, visual speech improved performance with congruent auditory speech at all distances and impaired performance with incongruent auditory speech at distances up to 20m, indicating that auditory speech recognition is influenced by visual speech even when encoded from distant faces. Implications of these findings for understanding visual and audiovisual speech recognition are discussed.

Increasing the benefits of eye-tracking devices in divided visual field studies of cerebral asymmetry

A wide range of methods has been proposed for ensuring central fixation in divided visual field studies of cerebral asymmetry. We present some of the problems associated with ensuring central fixation and argue that objectively monitoring fixation location with an eye-tracking device can provide the only accurate and, therefore, acceptable technique. However, the mere use of this equipment does not overcome all of the problems associated with controlling fixation location, and previous studies have overlooked the importance of providing feedback on fixation accuracy and the role of visual attention. We propose a straightforward method of accommodating both these influences in studies using eyetracking devices to control fixation location.

Word Superiority Over Isolated Letters: The Neglected Role of Flanking Mask Contours

When stimuli are presented in pattern-postmasked displays, performance is better for words than for isolated letters. Contemporary accounts of this word advantage emphasize the role played by mask contours that overlay the positions of letters in each stimulus; however, the precise effect of these overlying mask contours has never been empirically determined. The role of overlying and flanking (falling to the left and right of each word and isolated letter) mask contours in the word advantage over isolated letters was examined. A word advantage was obtained only when more flanking mask contours were shown with isolated letters than with words; when masks covered only the positions of letters in each stimulus, and thus no flanking mask contours were presented, the word advantage was removed or reversed. Implications for contemporary accounts of the word advantage over isolated letters are discussed.

Word superiority over isolated letters: The neglected case of forward masking

Previous research shows that when briefly presented alphabetic stimuli are followed by pattern masks, letters in words are reported more accurately than are isolated letters (the “Word-Letter Phenomenon,” or WLP); however, when these masks are replaced by blank fields, the WLP disappears. These findings have led to the popular notion that the WLP reflects selective masking of ongoing stimulus processing and so critically depends on the use of poststimulus masks. Here we report three experiments which re-examine the role of masking in the WLP by contrasting the effects of postmasked displays with the effects of premasked displays in which words and isolated letters werepreceded by a pattern mask and followedby a completely blank field. Despite the critical role generally assigned to poststimulus pattern masks, similar WLPs were obtained with pre- and postmasked displays. Implications for theories of word and letter recognition are discussed.

An experimental investigation of the pair bond in the callitrichid monkey,Saguinus labiatus

The strength and specificity of attraction between mated pairs of red-bellied tamarins (Saguinus labiatus) were tested in the laboratory. Test individuals were placed in a choice situation in which they could indicate their preference, by proximity and quality of behavior measures, to either their pair mate in an adjoining cage or an alternative in a second adjoining cage (same-sex animal, opposite-sex animal, or an empty cage). The test animals showed a significant preference to be in visual contact and proximity with their pair mates instead of the alternative when it was an animal of the same sex as the test individual or an empty cage. However, when the choice was between their pair mate and an animal of the opposite sex, no preference for their pair mate was apparent. No sex differences were found. It is concluded that attraction to a pair mate is not sufficient to maintain a pair bond, and when pairs ofS. labiatus breed monogamously, the pair relationship is likely to be maintained, at least in part, through aggression between same-sex individuals.

A connectionist model of visual-word recognition that accounts for interactions between mask size and word length

SummaryA connectionist model is described, which accounts for data showing a “mask appropriateness” effect in word and letter recognition. In a backward-masking paradigm, if the letter fragment masks that are used are of a similar size to the word or word fragment they are masking, performance is better than if the masks are longer or discontinuous (Jordan, 1990). The model simulates these effects by adding to the familiar architecture of the interactive activation model “length” units, which are stimulated whenever word units of a particular letter length are active, and “mask” units, which are stimulated by masks of particular sizes and in turn stimulate length units. Detailed predictions of the model are examined for both forward and backward masking, and are found to be in good accord with the data.