An improved technique for monitoring fixation in tachistoscopic tasks

A monocular lens mounted behind a stimulus screen was used to monitor fixation in a tachistoscopic recognition task. This technique was found superior to the often used “sideview technique” and as accurate as the method involving identification of a fixation stimulus. It was found that the “telescope technique” is preferable in those studies where presentation of a fixation stimulus might interfere with recognition or report of the experimental stimulus.     

Encoding and the rea for speech signals

A number of different possible explanations are distinguished for the findings on the right ear advantage (REA) for speech signals varied in their acoustic and phonetic properties. Two experiments are reported, using synthesized semivowels and vowels in monosyllable word frames. Both show REA. The detailed results of both experiments support the idea that a complicated “encoded” relationship between the acoustical stimulus and the response phoneme is a necessary condition for the REA, but that the encoding need only be signalled by an acoustical “trigger feature” in the stimulus; a task requiring a perceptual decoding is not necessary for REA to occur.     

Remembering, Familiarity, and Source Monitoring

Two experiments investigated recollective experience in a source monitoring task. Subjects saw an array of objects and performed, watched, or imagined actions involving pairs of objects. In a subsequent recognition test, subjects indicated whether their recognition judgements were made on the basis of conscious recollective experience (“remember” responses), or on some other basis such as familiarity (“know” responses). The proportions of correct “remember” responses for both objects and actions decreased from performed, through watched, to imagined actions, whereas the proportions of correct “know” responses were uninfluenced by the source of the memories. In addition, the relationship between recollective experience and accuracy of source judgement varied across sources. Source accuracy for performed actions was obtained only in “remember” responses, whereas source accuracy for imagined actions was obtained only in “know” responses. Source accuracy for watched actions was obtained in both “remember” and “know” responses. The findings suggest that the types of memory attributes available at retrieval determine the quality of subsequent memory experience, and it is proposed that memories with strongly self-referential attributes (arising from performed actions) powerfully cue recollective experience during retrieval.     

Response selection errors in spatial choice reaction tasks

In a “Consistent” spatial choice reaction task, the same spatial relationship obtains between each stimulus and its appropriate response. In an “Inconsistent” task this is not so. The present experiment concerns errors in Inconsistent tasks. Duncan (in press) has suggested that, when two spatial S-R relationships are involved in a task, the dominant type of error is a response bearing to the stimulus the wrong one of the two relationships. Duncan's results, however, may be described by a different generalization. Rabbitt and Vyas (1973) have suggested that confusions occur between responses which, when made correctly, bear similar spatial relationships to their stimuli. In the present experiment, a new Inconsistent task is studied. The results support the account of Duncan (in press) but provide no support for that of Rabbitt and Vyas (1973). Partly on the basis of error results, Duncan (in press) proposed a model of response selection in the spatial choice reaction task. Unlike previous accounts, this model is not based on a set of individual “S--R” associations; operations generating sets of S--R pairs are involved.     

Information processing by performers and observers in a paired associate learning task

The effects of two training procedures on learning and performance are compared. Performers select a response alternative for each stimulus on Trial 1 and receive feedback in terms of “Right” or “Wrong”. Observers receive the same information by listening to the experimenter. Experiment I tests the hypothesis that performers and observers are using a different learning strategy when there are only two response alternatives available for each stimulus on Trial 1. A recognition procedure was used on Trial 2; each stimulus was followed by four alternatives, two of them being the same as presented on Trial 1. Subjects have to recognize the two “old” alternatives. Performers are always better at recognizing the chosen alternative, whereas observers are better at recognizing the correct alternative. Experiment II extends the comparison between performers and observers to a task with four response alternatives on Trial 1. There are no longer differences in performance between the two training procedures.     

Tactile short-term memory

Subjects tried to recall the location of a tactile stimulus on the underside of the forearm after delays of 0, 3, 5, 10, 15, 30, 45 and 60 sec. When “rehearsal” was prevented by requiring subjects to count backwards during the delay, accuracy of recall decreased systematically reaching an asymptote after 45 sec. When subjects were left free to “rehearse,” this did not affect the decline in accuracy over the first 10 sec. Between 10 and 15 sec. there was a significant increase in accuracy followed by a slow decline which had not reached asymptote by 60 sec. It is suggested that tactile STM (short-term memory) depends on two processes, a fading sensory trace which is unaffected by distraction and a less labile system which does not appear to be verbal but which depends on “rehearsal.”     

Concrete and abstract terms and relations in testing a rule

Subjects have more difficulty in correctly testing a conditional rule stated in abstract form than the same rule given in “thematic” form. The “thematic” form of the rule involves both concrete terms and a concrete relation. Four experimental conditions were formed by combining concrete abstract terms and relations. Fifty subjects were tested in each condition. The results indicated that concrete-ness of the terms is the main factor leading to improved performance with “thematic” as against abstract material in the rule testing task.     

Driye-leyel and flexibility in paired-associate nonsense-syllable learning

“High-anxiety” and “low-anxiety” subjects, selected for extreme scores on the Taylor Anxiety Scale, learned a list of paired-associate nonsense syllables in the belief that they were undergoing an intelligence test. Both groups were then given a second list of paired associates to learn, the stimulus-items being the same as those of the first list but the responses being changed. Before the presentation of the second list, half the subjects in each group were given anxiety-increasing instructions and the remaining half were given reassuring instructions.

The results verified two predictions made from Hull's behaviour theory, using the concept of fear or anxiety as a secondary drive:—“high anxiety” subjects took more trials to master the second learning task than “low-anxiety” subjects; and there was a significant interaction between initial anxiety-level and type of instructions, such that “high-anxiety” subjects who received drive-increasing instructions had a worse performance in the second part than all other sub-groups. There was no indication that “low-anxiety” subjects were significantly affected by the type of instructions received. The “high-anxiety” group had greater difficulty than the “low-anxiety” group in learning the first list, but the difference was non-significant.     

A memory-based, Simon-like, spatial congruence effect: Evidence for persisting spatial codes

The Simon effect refers to the finding that in a task where stimulus location is irrelevant, reaction time is faster when stimulus and response locations are congruent than when they are not. Dominant theories of the Simon effect have generally attributed this spatial congruence effect to a spatial code automatically generated upon stimulus presentation. A common assumption of these theories is that this spatial code decays in less than a few hundred milliseconds following stimulus onset. We report two working-memory experiments suggesting a reexamination of this assumption—a Simon-like spatial congruence effect persisted over a delay of as long as 2400 ms. We propose that, in addition to generating short-lived perceptual codes, spatial information may be coded in working memory as part of the context associated with stimulus events. When reactivated by cues from the original event, such information may influence response selection and produce spatial congruence effects (in this case, positive when participants made a “yes” response and negative when they made a “no” response).     

Eliminating versus reducing smoking using pocket timers

I want to stop smoking, any number of procedures can be recommended as effective temporarily. However, follow-up data for these methods are often lacking or disappointing (Marston and McFall, 1971). The two purposes of this study were to (a) replicate and provide follow-up data for a promising method developed by Upper and Meredith (1970), and (b) compare the success of those who set out to “quit” versus those trying merely to “cut down”. The method used is based on the theory that if smoking can be brought under the control of a single stimulus rather than the usual, multiple elicitors, then it can be more easily modified. The stimulus used in this particular approach was the buzz of a pocket timer.     

An experiment in psoblem solying

Trial-and-error problems are described in terms of “stimulus” difficulty, which is a measure of the number of possible modes of response left to the individual when all the information given is taken into account; and “phenomenal” difficulty, which is a measure derived from the individual's performance. An experiment is described in which three types of problem were presented to human subjects. In all three problems the stimulus difficulty was calculable, stage by stage, in the solution. The problems differed in this stimulus difficulty and also in the qualitative nature of the information provided—from unequivocal to conditional. It is shown that the qualitative difference of the nature of the information bears most relationship to phenomenal difficulty. Some observations are made on the modes of solution adopted, and further experimental work is suggested.     

Binocular rivalry and stereoscopic depth perception

An investigation was made of stimulus factors causing retinal rivalry or allowing stereoscopic depth perception, given a requisite positional disparity. It is shown that similar colour information can be “filtered” out from both eyes; that stereopsis is not incompatible with rivalry and suppression of one aspect of the stimulus, and that the strongest cue for perception of stereoscopic depth is intensity difference at the boundaries of the figures in the same direction at each eye. Identity of colour can also act as a cue for stereopsis. The brightness of different monocular figures seen in the stereoscope in different combinations was estimated by a matching technique, and it is suggested that the perceived brightness is a compromise between the monocular brightness difference between figure and ground seen in relation to the binocular fused background, and the mean brightness of the figures. The results are discussed in terms of neurophysiological “on,” “off” and continuous response fibres.     

Visual pattern recognition: Size preprocessing re-examined

Template theories of visual pattern recognition assume the operation of preprocessing routines to deal with irrelevancies such as discrepancies in stimulus size. In three experiments where size was an irrelevant dimension, observers classified pairs of forms as either “same” or “different”. In Experiment I, the classification “different” was required when the stimuli shared the same form but a different orientation, and “same” when the stimuli shared the same form and orientation. Under these conditions RT was an increasing function of the magnitude of the size disparity between stimuli with equal slopes for “same” and “different” judgements. In Experiment II, “different” classifications were made to stimuli that had different forms, and “same” to figures with the same form. This stimulus set produced a size disparity function that interacted with response type; “different” responses had a shallower slope. Experiment III consisted of a mixed stimulus set drawn from both Experiment I and II. Stimuli that produced additive effects of size disparity and response type in Experiment I now produced an interaction between these two factors similar to the one observed in Experiment II. The results of these experiments are interpreted as evidence that previous contradictory results reported in the literature stem from differences in the way the stimulus set is constructed, and that size transformations can not be a necessary operation, at least when “different” judgements are made. The results are problematic for the view that size disparity effects in matching tasks are easily interpretable in terms of a primitive size normalization stage that precedes any comparison operations.     

Does intermodal equivalence exist between heteromodal stimulus dimensions or between stimulus values on those dimensions?

In a same--different judgement task with successively presented signals, subjects matched dots in different vertical positions and tones of different frequencies intramodally and intermodally. The first and second stimuli of trials in each of the four modality conditions were drawn from a set consisting of two, three or five alternatives. In all intermodal set size conditions, the dimensions of pitch and vertical position were related by the same equivalence rule. While intramodal performance improvement depended only on the total number of practice trials at matching on the relevant dimensions, intermodal performance improvement appeared to be related to the number of trials practice with each heteromodal stimulus pairing in a particular set. After performance had approached asymptotic level neither intramodal nor intermodal matching reaction time depended on set size. Mean “same” reaction time was less than mean “different” reaction time, and this difference was greater for intermodal matching than for intramodal matching. The results indicated that intermodal equivalence exists between discrete stimulus values on heteromodal dimensions rather than between the dimensons themselves.     

The effect of training and handedness on the performance of two simple motor tasks

In the first experimental series nine right-handed and nine left-handed subjects were tested on each side on two tasks. The first task measured the accuracy of reproduction of pressure in attempted extension of the elbow joint, and the second the speed of oscillation of attempted flexion and extension of the elbow joint. The results showed no significant difference in performance on the two sides in the accuracy task but a significant difference in performance on the speed task.

In the second experimental series the effect of 15-minutes daily training on each of two tasks over a four-week period was investigated on six subjects. The two tasks were the same as those used in the first experimental series, and attempted movement at the metacarpo-phalangeal joint as well as the elbow joint was studied. The mean results of all subjects showed a significant reduction in the mean error of the “accuracy” task over the training period for both the finger and arm. However, further analysis suggests that this may have been due to a clarifying of the subjects' concept of the target value rather than an improvement in his ability to grade the appropriate muscle contractions. A significant increase in the mean speed of oscillation over the training period was also recorded for both finger and arm. This improvement was accompanied in most instances by a corresponding decrease in variation of cycle length of the individual oscillations, which is interpreted as an improvement in the subjects' “timing” of the appropriate muscle contractions.     

Discriminability and central intermittency in same-different judgements

Four sets of paired visual stimuli (OO, XX, XO, or OX) were judged by 48 subjects to be either “same” or “different.” Decision latencies of the same and different judgement were studied as a function of the inter-stimulus interval (ISI). In Experiments I and II, in which stimulus durations were 70 millisec., decision latencies showed marked increases when the ISI was reduced to 100 millisec., but in Experiments III and IV, in which the stimulus durations were only 40 millisec., comparable increases did not occur until the ISI was reduced to 50 millisec. These increases were more marked for “same” than for “different” judgements, although overall decision latencies were generally shorter for “same” judgements. The effects of varying ISIs and stimulus durations are interpreted in terms of masking; they fail to support an hypothesis of central intermittency.     

Crossmodal integration in the identification of consonant segments

Although speechreading can be facilitated by auditory or tactile supplements, the process that integrates cues across modalities is not well understood. This paper describes two “optimal processing” models for the types of integration that can be used in speechreading consonant segments and compares their predictions with those of the Fuzzy Logical Model of Perception (FLMP, Massaro, 1987). In “pre-labelling” integration, continuous sensory data is combined across modalities before response labels are assigned. In “post-labelling” integration, the responses that would be made under unimodal conditions are combined, and a joint response is derived from the pair. To describe pre-labelling integration, confusion matrices are characterized by a multidimensional decision model that allows performance to be described by a subject's sensitivity and bias in using continuous-valued cues. The cue space is characterized by the locations of stimulus and response centres. The distance between a pair of stimulus centres determines how well two stimuli can be distinguished in a given experiment. In the multimodal case, the cue space is assumed to be the product space of the cue spaces corresponding to the stimulation modes. Measurements of multimodal accuracy in five modern studies of consonant identification are more consistent with the predictions of the pre-labelling integration model than the FLMP or the post-labelling model.     

Visual search without eye movement

Two experiments have been made on the problem of visual search using six patterns which were geometrically simple, and familiar to the subject.

In each case the subject's task was to say where, among the complex of patterns, a particular pattern (the “test object”) appeared when the exposure of the whole display was so brief as to prevent scanning by the eyes. He could be informed visually (in Experiment I) or verbally (in Experiment II) which pattern was to be regarded as the “test object.”

In both experiments it was found that foreknowledge of what was to be the test object gave a significantly higher standard of accuracy than knowledge given later. This suggests that something analogous to visual search can occur without eye movements.     

Neural correlates of partial transmission of sensorimotor information in the cerebral cortex

Using single neuron recordings in monkey primary motor (MI) cortex, two series of experiments were conducted in order to know whether response preparation can begin before perceptual processing finishes, thus providing evidence for a temporal overlap of perceptual and motor processes.

In Experiment 1, a “left/right, Go/No-Go” reaction time (RT) task was used. One monkey was trained to perform wrist flexion/extension movements to align a pointer with visual targets. The visual display was organized to provide a two-dimensional stimulus: side (an easy discrimination between left and right targets) which determined movement direction, and distance (a difficult discrimination between distal and proximal targets) which determined whether or not the movement was to be made. Changes in neuronal activity, when they were time-locked to the stimulus, were almost similar in the Go and No-Go trials, and when they were time-locked to movement onset, were markedly reduced in No-Go as compared to Go trials.

In Experiment 2, a stimulus-response compatibility (SRC) task was used. Two monkeys were trained to align a pointer with visual targets, on either left or right. In the spatially “compatible” trials, they had to point at the stimulus position, whereas in the “incompatible” trials, they had to point at the target located in the opposite side. For 12.5% of neurons, changes in activity associated with incompatible trials looked like changes in activity associated with movements performed in the opposite direction during compatible trials, thus suggesting the hypothesis of an automatic activation of the congruent, but incorrect response.

Results of both experiments provide evidence for a partial transmission of information from visual to motor cortical areas: that is, in the No-Go trials of the first task, information about movement direction, before the decision to perform or not this movement was made, and, in the incompatible trials of the SRC task, information about the congruent, but incorrect response, before the incongruent, but correct response was programmed.     

An observation on set and visual comparison processes

Tasks involving the comparison of sequentially presented stimulus items to determine identity have generally only required interpretation in terms of simple matching. Some studies have attempted to show effects of selective set in these tasks but with little success except in tasks involving comparison of sentences with pictures. By simplifying the task a reliable set effect is demonstrated, showing that a mismatch of certain stimulus attributes only has an identifiable effect on a subject's reaction-time if he may reasonably be supposed to know that the attribute is critical and is set to examine stimulus items for the attribute. Such conditions result in a relatively fast judgement. The finding suggests that the sequential “same“/“different” judgement is a richer source of data concerning recognition and comparison than has been supposed.