Albrecht W. Inhoff

Isolating attentional systems: A cognitive-anatomical analysis

Recently our knowledge of the mechanisms of visual-spatial attention has improved because of studies employing single cell recording with alert monkeys and others using performance analysis of neurological patients. These studies suggest that a complex neural network that includes parts of the posterior parietal lobe and midbrain is involved in covert shifts of visual attention. Is this system an isolated visual attentional module or is it part of a more general attentional system? Our studies employ the dual-task technique to determine whether covert visual orienting can take place while a person’s attention is engaged in a language processing task. We find clear evidence of interference between the two tasks, which suggests some common operations. However, the results also indicate that whatever is common to the two tasks does not have the same anatomical location as that of visual-spatial attention.

Chapter 2 – Definition and Computation of Oculomotor Measures in the Study of Cognitive Processes

Publisher Summary This chapter reviews methodological choice points that need to be considered when raw data are used to define basic oculomotor events, such as fixations and saccades. Oculomotor measures provide distinct methodological advantages in the study of cognitive and perceptual processes. They appear sensitive to a wide range of “cognitive processes” and can be obtained under relatively natural task conditions. Derivation and use of these measures is not, however, straightforward. The chapter also considers the usage of these oculomotor events for the indexing of perceptual and cognitive processes. Attention is given to viewing duration measures, as these are used as the primary indicator of cognitive processes in eye movement research. The discussion is limited in that the raising of measurement-related and methodological issues is not followed by the presentation of specific solutions. There are no “de facto” standard measurements that define basic oculomotor events (fixations and saccades). Furthermore, processing assumptions that underlie the translation of oculomotor events into measures of cognitive processes are increasingly challenged. It remains unclear whether some definitions of oculomotor events and some oculomotor measures are more effective than others.

Mindless reading: Eye-movement characteristics are similar in scanning letter strings and reading texts

The purpose of the present study was to compare the oculomotor behavior of readers scanning meaningful and meaningless materials. Four conditions were used—a normal-text-reading control condition, and three experimental conditions in which the amount of linguistic processing was reduced, either by presenting the subjects with repeated letter strings or by asking the subjects to search for a target letter in texts or letter strings. The results show that global eye-movement characteristics (such as saccade size and fixation duration), as well as local characteristics (such as word-skipping rate, landing site, refixation probability, and refixation position), are very similar in the four conditions. The finding that the eyes are capable of generating an autonomous oculomotor scanning strategy in the absence of any linguistic information to process argues in favor of the idea that such predetermined oculomotor strategies might be an important determinant of eye movements in reading.

Covert Attention and Eye Movements during Reading

Eye movements were monitored during the reading of spatially transformed text in order to examine covert attentional processes in reading. In some conditions, the sequence of letters within a word was congruent with (i.e. in the same direction as) the sequence of words in the sentence; in other conditions the direction of letters within words and the direction of words in the sentence were incongruent. In addition, the window of visible text was varied so that in some conditions only the fixated word (and all preceding words) were visible, whereas in other conditions the fixated word and the succeeding word were both visible. Readers were able to extract more parafoveal information from text when the words themselves were normal than when the letters within the words were transformed. However, with practice, readers were able to use some parafoveal information even when the words were transformed. The most important finding was that the congruity of the word and letter order had no reliable effect on the ability to extract parafoveal information and influenced reading performance only when the words themselves were normal. We conclude that covert attention in reading is not a letter-by-letter scan that sweeps across the page, but either an asymmetric spotlight held constant on each fixation or a shifting of an attentional spotlight extending across multiletter units (possibly words) with the direction of shifts of attention closely coupled to the direction of eye movements.

The effects of morphology on the processing of compound words: evidence from naming, lexical decisions and eye fixations.

The use of lexemes during the recognition of spatially unified familiar English compounds was examined in naming, lexical decision and sentence-reading tasks by manipulating beginning and ending lexeme frequencies while controlling overall compound frequencies. All tasks revealed robust ending lexeme frequency effects, with compound processing being more effective when the ending lexeme was a high-frequency word. Beginning lexeme frequency effects were more elusive and dependent on task demands. Eye movements, recorded during sentence reading, also indicated that the effects of ending lexemes occurred after the first fixation during compound viewing. Together, the results suggest either that the ending lexeme is used as an access code to locate the meaning of the full compound word or that its meaning is coactive with the meaning of the full compound.

The perceptual span and oculomotor activity during the reading of Chinese sentences

Eye-movement-contingent display changes were used to control the visibility of characters during the reading of Chinese text. Characters outside a window of legible text were masked by dissimilar characters, and effects of viewing constraints were ascertained in several oculomotor measures. The results revealed an asymmetric perceptual span that extended 1 character to the left of the fixated character and 3 characters to its right. The size of right-directed saccades extended across 2 to 2 1/2 character spaces, indicating that the perceptual spans of successive fixations overlapped slightly and that some linguistic information was integrated across fixations. The relatively small spatial overlap of successive spans appears to reflect a text-specific process. However, the results also revealed substantial similarities in the coding of morphographic Chinese and alphabetic English texts, indicating that text-specific coding routines are subordinated to general coding principles.

Parafoveal processing of words and saccade computation during eye fixations in reading

Studied parafoveal word processing during eye fixations in reading to answer two questions: (a) Is the processing of parafoveally available words limited to the identification of beginning letters? (b) Does the parafoveal processing of words affect the following interword saccade? Reading afforded either no parafoveal preview, preview of beginning trigrams, preview of ending trigrams, or preview of the whole parafoveal word. Previews were controlled by replacing original letters either with Xs or dissimilar letters. Preview benefits were larger for the whole word previews than for beginning or ending trigram previews. X-masks yielded preview benefits from intact beginning and ending trigrams but dissimilar letter masks yielded benefits from beginning trigrams only. Saccades were larger for whole word previews than for no previews. These results support Logogen-type models of word recognition and a model of saccade computation that posits a time-locked functional relation between the acquisition of parafoveal word information and the positioning of each fixation.

Encoding of text, manual movement planning, and eye-hand coordination during copytyping.

Typing span and coordination of word viewing times with word typing times in copytyping were examined. In Experiment 1, typists copied passages of text while their eye movements were measured. Viewing location was determined during each eye fixation and was used to control the amount of usable visual information. Viewing constraints decreased interword saccade size when fewer than 7 character spaces of text were visible to the right of fixation and increased interkeypress times when fewer than 3 character spaces of text were visible. The eye-hand span amounted to 2.8 character spaces. Experiment 2 revealed increases in word typing times and word viewing times as biomechanic typing difficulty increased and word frequency decreased. These findings are consistent with a model of eye-hand coordination that postulates that eye-hand coordination involves central and peripheral processes.

Lexical access during eye fixations in reading: Are word access codes used to integrate lexical information across interword fixations? ☆

Eye fixation records during reading were obtained to test whether lexical access of a word is distributed across successive interword fixations. Specifically, prelexical analyses discerning the word access code could be performed during the parafoveal processing of a word and lexical access could be completed during the words subsequent fixation. A series of sentences was read with each sentence containing either a 6-letter compound word (e.g., cowboy), a 6-letter pseudocompound word (e.g., carpet), or a 6-letter control word (e.g., mirror). Reading occurred under four parafoveal text preview conditions affording either no usable preview, preview of a words beginning three letters, preview of a words beginning four letters, or preview of a complete parafoveal word. Previews of three and four letters either corresponded to linguistically defined subword units (putative word access codes) or violated these units. The results showed that parafoveal preview benefits from 3- and 4-letter sequences were unaffected by the linguistic status of previewed letters, indicating that word access codes are not used to integrate lexical information across interword fixations. Parafoveal previews of whole words revealed, however, effects of linguistic status. Preview benefits were largest for pseudocompound words which comprised high frequency beginning and ending subword constituents and smallest for control words which did not contain subword constituents with lexical representations. These results support models of parafoveal word recognition which posit, first, that all letters of a parafoveal word contribute to the early phase of word identification and, second, that these letters form mutually reinforcing letter coalitions.

Social anxiety and difficulty disengaging threat: Evidence from eye-tracking

Theoretical models of social phobia propose that biased attention contributes to the maintenance of symptoms; however these theoretical models make opposing predictions. Specifically, whereas Rapee and Heimberg (1997) suggested the biases are characterised by hypervigilance to threat cues and difficulty disengaging attention from threat, Clark and Wells (1995) suggested that threat cues are largely avoided. Previous research has been limited by the almost exclusive reliance on behavioural response times to experimental tasks to provide an index of attentional biases. The current study evaluated the relationship between the time-course of attention and symptoms of social anxiety and depression. Forty-two young adults completed a dot-probe task with emotional faces while eye-movement data were collected. The results revealed that increased social anxiety was associated with attention to emotional (rather than neutral) faces over time as well as difficulty disengaging attention from angry expressions; some evidence was found for a relationship between heightened depressive symptoms and increased attention to fear faces.