Four experiments are reported which examined memory capacity and retrieval speed for pictures and for words. Single-trial learning tasks were employed throughout, with memory performance assessed by forced-choice recognition, recall measures or choice reaction-time tasks. The main experimental findings were: (1) memory capacity, as a function of the amount of material presented, follows a general power law with a characteristic exponent for each task; (2) pictorial material obeys this power law and shows an overall superiority to verbal material. The capacity of recognition memory for pictures is almost limitless, when measured under appropriate conditions; (3) when the recognition task is made harder by using more alternatives, memory capacity stays constant and the superiority of pictures is maintained; (4) picture memory also exceeds verbal memory in terms of verbal recall; comparable recognition/recall ratios are obtained for pictures, words and nonsense syllables; (5) verbal memory shows a higher retrieval speed than picture memory, as inferred from reaction-time measures. Both types of material obey a power law, when reaction-time is measured for various sizes of learning set, and both show very rapid rates of memory search.
From a consideration of the experimental results and other data it is concluded that the superiority of the pictorial mode in recognition and free recall learning tasks is well established and cannot be attributed to methodological artifact.
Monocular visual field defects were studied in two monkeys. In one, the macular retina was destroyed by photocoagulation, producing a central scotoma and consistent 5° eccentric fixation. In a second animal the effects of removal of macular projection area in striate cortex and subsequent photocoagulation of the macula were compared. The cortical operation produced a partial field defect, i.e. a region of diminished sensitivity but not a scotoma, which became with practice much smalle than the region of retina whose primary projection area had been ablated. A 10° eccentric fixation was observed. Following the second, retinal, operation a macular scotoma was demonstrated whose size and position corresponded closely with the area of retinal destruction as determined by photography of the fundus and later histological examination of the retina.
An experiment was designed to test the hypothesis that judgments of absolute pitch rely on a sub-liminal tinnitus (ringing in the ears) which is used as a reference tone. In a series of 144 pairs of trials, the subject alternately measured his own tinnitus; and made absolute judgments of pitch by setting a variable tone to match the frequency of a named (target) note. He judged the frequency of the 48 notes spanning the 4 octaves from A flat = 106 Hz to G = 1584 Hz. It was found that his judgments of the pitch of named notes were significantly more accurate (P < 0.01) than had been predicted from the variability of the pitch of his tinnitus. Also, there was only a very low correlation (r = 0.246) between the absolute pitch judgments and the tinnitus settings made on the same trial. This indicates that the hypothesis is false. Nevertheless, it is argued that absolute pitch judgments may not require a channel capacity of more than 3 bits per decision.
A three-choice reaction-time task was used to investigate the source-of-stimulation effect, that is, the tendency for subjects to react faster and more accurately to a stimulus if the spatial locations of the stimulus and the response correspond than if they do not. Auditory stimuli varied on dimensions of tonal frequency and spatial location, although only the former was relevant for response selection. Responses were found to be faster for the conditions in which stimulus location and response location corresponded than for those in which they did not, but stimulus location had no effect on differences between the two hands with bimanual responses. These results support the hypothesis that the source-of-stimulation effect is due to response plans which interact at a level prior to the programming of the motor response.This work was performed while the first author was in receipt of a Science Research Council Studentship.Now at MRC Applied Psychology Unit, 15 Chaucer Road, Cambridge CB2 2EF.
In five experiments visual processing of sentences containing either a more frequent or a less frequent usage of an ambiguous word was examined. When prior or subsequent context was pragmatically related to the relevant sense of the ambiguous word, sentences intending the more frequent sense produced longer ambiguity detection times and shorter immediate comprehension times than sentences intending the less frequent sense. This relative frequency effect was not obtained in comprehension of corresponding unambiguous sentences containing relatively high or low frequency unambiguous synonyms of the senses. These results suggest that access of ambiguous word-senses tends to occur in order of relative frequency, and that multiple access of senses tends only to occur for low frequency usages. When the preceding verb imposed selection constraints on which sense could follow, the frequency effect did not occur consistently; and it was virtually eliminated when biasing context took the form of a previous sentence containing an unambiguous synonym of the relevant sense. Implications for models of access of unambiguous words in sentences, as well as for models of processing ambiguous sentences, are considered.
This study demonstrates the role of microfluctuations of accommodation in the viewing of the concentric ring illusion. Four experiments were carried out. Experiment I consisted of changing the distance between the illusion and the eyes but retaining visual angle, luminance and pupil size constant. In Experiment II, the accommodation of the eyes is paralysed by a cycloplegic. In Experiment III, the illusion is shown to a monocular aphakic and in Experiment IV, the exposure time is varied between 1/100 and 5 sec. Furthermore, a series of observations compared the concentric ring illusion seen with both eyes simultaneously. The evidence provided by the results of these experiments plus others discussed provide evidence that the concentric ring illusion is caused by the microfluctuations of accommodation.
Semantic memory retrieval for verifying category–-example associations was tested by a speed accuracy tradeoff method: present the category for 2 s, present a correct or incorrect example followed, after a variable lag (0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1, 2, or 3 s), by a signal to make a “yes-no” response in about 0.2 s. Although the strength of the category–-example association is higher for high dominance examples of a category, retrieval dynamics did not vary with dominance level. Recognition for category–-example associations appears to be a direct-access (parallel) retrieval process. Priming a category by repeated testing of the same category over three consecutive trials had no effect on either asymptotic strength or retrieval dynamics. Partitioning into short, medium, and long latency responses at each lag produced microtradeoff functions which did not lie on the same macrotradeoff function. Retrieval dynamics were invariant with long-term practice.
Hypothesized that nonvisual aiming accuracy (e.g., in darkness) is linearly related to distance and independent of movement speed. In an experiment with 30 right-handed normally visioned undergraduates, results show the theory to be partly true: a linear relationship to distance was demonstrated, but an optimum speed was found. Constant errors showed interesting trends, displaying the usual range effect but also being affected by movement time. A small irreducible component in these errors was found which was considered to be caused by physiological tremor. Results are easily encompassed in the feedback theory but would be difficult for an information theory based model of movement control. (22 ref.) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This note describes a way of modifying a tape recorder for producing accurately controllable delays for experiments with delayed auditory feedback. Any value of delay from 80 millisec. to 1.2 sec. can be obtained to the nearest millisec., and the range could be extended by some minor changes. The delay is continuously monitored on a digital electronic timer.
The effects of direct brain infusions of acetoxycycloheximide (an inhibitor of protein synthesis; ACXH) on acquisition, storage and recall of memory for one-trial appetitive learning were examined in five experiments. ACXH was infused into the rats' hippocampi through implanted cannulas. Control subjects received an equal volume of physiological saline. ACXH was infused (a) 5 h before acquisition, (b) 5 hr before commencement of recall tests, and (c) immediately after acquisition. Each subject's general motor activity was recording during testing. The results indicate that (1) ACXH has similar effects on appetitive and avoidance learning. (2) ACXH administered immediately after acquisition, has no effect on memory. (3) At 4 hr after acquisition memory is affected by ACXH. (4) Short-term memory is unaffected by ACXH and can exist independently of long-term memory. (5) ACXH consistently reduces general motor activity.Department of Psychology, University of Exeter, Washington Singer Laboratories, Exeter, Devon
Four lists of Chinese words in a 2 × 2 factorial design of visual and acoustic similarity were used in a short-term memory experiment. In addition to a strong acoustic similarity effect, a highly significant visual similarity effect was also obtained. This was particularly pronounced in the absence of acoustic similarity in the words used. The results not only confirm acoustic encoding to be a basic process in short-term recall of verbal stimuli in a language other than English but also lend support to the growing evidence of visual encoding in short-term memory as the situation demands.
This study attempts to discover why items which are similar in sound are hard to recall in a short-term memory situation. The input, storage, and retrieval stages of the memory system are examined separately. Experiments I, II and III use a modification of the Peterson and Peterson technique to plot short-term forgetting curves for sequences of acoustically similar and control words. If acoustically similar sequences are stored less efficiently, they should be forgotten more rapidly. All three experiments show a parallel rate of forgetting for acoustically similar and control sequences, suggesting that the acoustic similarity effect does not occur during storage. Two input hypotheses are then examined, one involving a simple sensory trace, the other an overloading of a system which must both discriminate and memorize at the same time. Both predict that short-term memory for spoken word sequences should deteriorate when the level of background noise is increased. Subjects performed both a listening test and a memory test in which they attempted to recall sequences of five words. Noise impaired performance on the listening test but had no significant effect on retention, thus supporting neither of the input hypotheses. The final experiments studied two retrieval hypotheses. The first of these, Wickelgren's phonemic-associative hypotheses attributes the acoustic similarity effect to inter-item associations. It predicts that, when sequences comprising a mixture of similar and dissimilar items are recalled, errors should follow acoustically similar items. The second hypothesis attributes the effect to the overloading of retrieval cues which consequently do not discriminate adequately among available responses. It predicts maximum error rate on, not following, similar items. Two experiments were performed, one involving recall of visually presented letter sequences, the other of auditorily presented word sequences. Both showed a marked tendency for errors to coincide with acoustically similar items, as the second hypothesis would predict. It is suggested that the acoustic similarity effect occurs at retrieval and is due to the overloading of retrieval cues.
Experiment I studied short-term memory (STM) for auditorily presented five word sequences as a function of acoustic and semantic similarity. There was a large adverse effect of acoustic similarity on STM (72·5 per cent.) which was significantly greater (p < 0·001) than the small (6·3 per cent.) but reliable effect (p < 0·05) of semantic similarity.
Experiment II compared STM for sequences of words which had a similar letter structure (formal similarity) but were pronounced differently, with acoustically similar but formally dissimilar words and with control sequences. There was a significant effect of acoustic but not of formal similarity.
Experiment III replicated the acoustic similarity effect found in Experiment I using visual instead of auditory presentation. Again a large and significant effect of acoustic similarity was shown.
The following three studies of single-probe recognition memory set out to show the effect on the signal-detectability measures of d′ and β (Tanner and Swets, 1954) of variations in the acoustic similarity of interfering material, which may either precede or follow the item to be remembered (proactive or retroactive interference —PI or RI). The first experiment studies a situation employed by Wickelgren (1966a), who reported that acoustically similar RI substantially reduced d′. It is shown that this effect could have been due to biases in Wickelgren's original designs, and that when a bias-free design is used, the fall in d′ is only of borderline significance.
To investigate this problem further, a design was evolved in which two items were presented for memorizing, which varied in acoustic similarity to each other, and (after a distracting task) a probe was presented with one of three questions: Was this the first item of the pair? Was it the second? or, Did it occur in either position? In the first case, recognition-memory with RI of varying acoustic similarity was being studied, and as in the first experiment, it was found that similarity slightly reduced d′. With the second question, PI effects were being studied, and here negligible differences were found. With the third type of question, a “location-free” test, no effects of similarity were found. The last result rules out Posner's (1967) “acid-bath” explanation of similarity effects in interference: an explanation in terms of “differentiation” (or “filtering”) was also invalidated by the results of a third experiment, in which the same effects were found even though similarity varied only between stimulus items and interference, and not between these and the probe. Wickelgren's (1966b) associative model appears to have least difficulty in accommodating these results, though even this needs certain ad hoc assumptions to be able to do so.
It has been shown that short-term memory (STM) for word sequences is grossly impaired when acoustically similar words are used, but is relatively unaffected by semantic similarity. This study tests the hypothesis that long-term memory (LTM) will be similarly affected. In Experiment I subjects attempted to learn one of four lists of 10 words. The lists comprised either acoustically or semantically similar words (A and C) or control words of equal frequency (B and D). Lists were learned for four trials, after which subjects spent 20 min. on a task involving immediate memory for digits. They were then asked to recall the word list. The acoustically similar list was learned relatively slowly, but unlike the other three lists showed no forgetting. Experiment II showed that this latter paradox can be explained by assuming the learning score to depend on both LTM and STM, whereas the subsequent retest depends only on LTM. Experiment III repeats Experiment I but attempts to minimize the effects of STM during learning by interposing a task to prevent rehearsal between the presentation and testing of the word sequences. Unlike STM, LTM proved to be impaired by semantic similarity but not by acoustic similarity. It is concluded that STM and LTM employ different coding systems.
Previous work has shown that in searching for existing or absent “e.s” in printed prose, the presence or absence of silent “e.s” was less likely to be detected than that of pronounced “e.s.” It was suggested that the acoustic or kinaesthetic “image” was searched for evidence of an “e” in addition to the visual stimulus and that evidence from both sources was considered in making the appropriate response.
The present experiment employs mainly substitutive errors within words, which may or may not change their pronunciation. The results suggest that the form of the acoustic correlates has no bearing upon whether the words are detected as wrongly spelt, but that the presence or absence of an acoustic event corresponding in time to the spatial location of the error is important.
Several investigations have reported problems in demonstrating for vowels the phenomena of backward masking and right ear advantage so easily demonstrated for consonants. An experiment is reported on the dichotic backward masking (BM) of acoustically similar and dissimilar sets of vowels in consonant-vowel syllables. The results suggest that increasing perceptual difficulty by varying the acoustic similarity of the stimulus set augments BM. A second experiment showed that the right ear advantage (REA) was augmented by manipulating the acoustic similarity of the stimulus set and by decreasing intelligibility through the addition of noise. This and other evidence was employed to ascribe variations in both REA and BM to the interaction of perceptual processing time with information decay in precategorical acoustical storage. It is argued that this process interaction underlies statistical interactions in dichotic data which show that variations in difficulty (discriminability, noise addition, brain deterioration) affect most adversely the least favoured items (those presented earlier, those on the unattended ear, those on the left ear).Now at: Central School of Speech and Drama, Eton Avenue, London NW33HY, U.K. to where requests for reprints should be directed.
Protein-deprived rats were given, on one day, a balanced mixture of amino acids followed by access to protein-free food having a distinctive odour. On another day, an imbalanced (histidine-free) amino acid mixture was given just before food having another odour. The rats afterwards preferred the balance-paired odour to the imbalance-paired odour. The preference was acquired whether the duration of odour presentation, or the amount of odourised food taken, was kept constant on the two conditioning days. Retention of the preference seemed unattenuated after 4 weeks. An attraction to the balance-paired odour (relative to odours paired with a water load) contributed to the acquired preference. There was also a relative aversion to unfamiliar odours when they had been paired with imbalance. Such acquired chemosensory control of preferences, together with an anorexigenic effect of imbalanced amino acid mixtures, can account for characteristics of feeding behaviour under conditions in which the diet is deficient in an essential amino acid.
Three experiments investigated the effect of post-trial stimulation on conditioning. Rats were trained in a conditioned suppression procedure in which only half of the CS presentations were followed immediately by a shock reinforcer. Presenting a second, post-trial, shock 8 s after the end of reinforced CS presentations increased resistance to extinction in Experiment I and facilitated conditioning in Experiment II relative to a condition in which the same post-trial shock was delivered 8 s after non-reinforced trials. Experiment III demonstrated that prior exposure to pairings of the shock reinforcer and the post-trial shock also enhanced subsequent conditioning, and thus ruled out an explanation of the facilitation in terms of the surprising nature of the post-trial stimulation.
The effect of interstimulus interval (ISI) variation on the acquisition of a classically conditioned emotional response was investigated using a one-trial conditioning procedure. The optimum ISI was found to be 10 s with a bidirectional gradient for conditioned suppression at ISI above and below 10 s. Control groups demonstrated that conditioning was not a function of either pseudoconditioning, sensitization or stimulus novelty.
Rats were trained and tested on an avoidance task in a shuttle box. The change in the performance of the control rats over two sessions was found to be a U-shaped function of the interval between the sessions. The change in performance of rats injected with physostigmine prior to the second session was also found to be a U-shaped function of the intersession interval, although the drug was shown to impair avoidance behaviour. These results are consistent with those of Hamburg (1967) and of Biederman (1970), and support the general contention that cholinergic mechanisms in the brain are involved in the control of avoidance and escape behaviour in the rat. They do not, however, necessarily support the hypothesis advanced by Deutsch (1969, 1971) to describe a biochemical basis of learning and memory, especially if it is used to explain the effects of cholinesterase inhibitors on avoidance behaviour in the shurtlebox.
To obtain an estimate of the learning ability of opossums, five tame ones were trained on a series of position reversals to a criterion. With 4 trials per day there was no consistent improvement over a series of 15 reversals. When each daily session was increased to as many trials as needed to reach criterion, errors dropped sharply, indicating the formation of a position learning set. Upon return to 4 trials per day, 3 of 4 animals continued to perform with few errors, showing transfer of learning set. Opossums do more poorly than rats on this task, which is in agreement with the relative phyletic level of the two species.
Cockroaches can be trained to keep their metathoracic leg out of a saline solution. Isolated metathoracic ganglia learnt faster than headless animals, which in turn learnt faster than intact animals. Extinction took longer in the isolated ganglion than in the other two preparations. Extinction times increased with increasing dose of orotic acid, a precursor of RNA. Orotic acid did not systematically affect the times for acquisition and reacquisition of the learnt response.Department of Psychology, University of Birmingham, Birmingham, 15.The School of Pharmacy, Portsmouth Polytechnic, Portsmouth.
A serial recall experiment comparing visual and auditory presentation is reported which demonstrates that, under certain conditions, there is an auditory advantage in the pre-recency (1–6) as well as the recency (7–8) serial positions. Presentation modality was combined factorially with five levels of a concurrent writing task, which had to be completed for each to-be-remembered digit during presentation: NC, no concurrent task; XX, writing two crosses; DX, writing each digit followed by a cross; XD, the converse of DX; and DD, writing each digit twice. When presentation was visual, there was a monotonic (non-decreasing) trend in the recall errors going from NC to DD (in above order) for both the pre-recency and recency positions on average. With an auditory presentation, however, the trend was more gradual, though still monotonic. For the pre-recency items, an auditory advantage was obtained with conditions XX, XD and DD, but not for NC and DX. Additionally, with an auditory presentation, there was no evidence of a difference between NC and XX, nor between DX and XD. It is argued that both pre-categorical acoustic storage and residual activation effects, engendered in a logogen system (Morton, 1970) by the repetition “structure” of the concurrent tasks, helped to determine the attentional capacity available for secondary (elaborative) rehearsal and, in turn, set the levels of recall.
The three experiments described in this paper were intended to show whether voluntary attention to a particular part of the peripheral visual field had any effect on the accuracy of the subject's perception. Test objects near to threshold value (for acuity or for changes in luminance) were used. The experiments were also designed to study the possible distracting effect of other stimuli presented simultaneously in different parts of the field.
In Experiment 1 the subject could be given foreknowledge of the position in which an acuity test object would appear. In Experiment 2 the signal of where to attend was given simultaneously with the exposure of an acuity test object. In Experiment 3 differential thresholds for luminance were investigated by methods similar to those used in Experiment 2.
It was found in all these cases that the instructions to attend to a particular part of the peripheral field had no significant effect on perception unless there were simultaneously exposed “competing” stimuli in other parts of the field. The results support the view that, in peripheral vision, attention acts selectively on the immediate memory trace only when there is a complex pattern of stimulation.
Burns and Pritchard's (1971) explanation of the Poggendorff illusion is criticized. An experiment was designed to determine whether the acute angle plays any role in the perception of the illusion. The results showed that (i) an inducing line which crossed a test-line was highly effective in altering the apparent orientation of the test line, (ii) an inducing line forming an acute angle with a test-line had a small effect in changing the apparent orientation of the test-line, and (iii) an acute angle which formed part of the Poggendorff configuration produced an effect opposite to that predicted by the view that acute angles are perceptually enlarged.Now at the Department of Psychology and Sociology, Mount Allison University, Sackville, New Brunswick, Canada.
Inhibition of ad libitum feeding in rats was induced by hypertonic NaCl injections. Though osmotic loads of sufficient size were capable of abolishing feeding completely for a time, the effect was not as large as had been predicted from a hypothesis of strictly linear subtractive inhibition. Feeding at a low level of hunger seems to be somewhat less affected by osmotic inhibition than feeding on a deprivation schedule. Inhibition of feeding was also produced by deprivation of water, and both the inhibition of food intake during deprivation, and the disinhibition by subsequent drinking indicated that the amount of inhibition of food intake is a non-linear (accelerating) function of water deficit. A model of the process indicating that the thirst signal undergoes a non-linear transformation before being subtracted from the signal corresponding to food demand is proposed.
Subjects were adapted for 45 s to a 5 cycle per degree grating, tilted 10° from the vertical, and at one of four levels of luminance contrast. Estimates of the slope of the grating, or of a single line which replaced the grating, were obtained before and after the period of adaptation by the subject's setting of a single reference line which was located 3° from the edge of the grating. In Experiment I the fixation area was at the centre of the grating, so that half of the grating fell on each retinal hemifield. The reference line was set to a tilt further from the vertical following the period of adaptation, indicating either a change in the apparent orientation of the grating or the reference line. In Experiment II, where the fixation area was midway between the grating and the reference line, so that line and grating appeared in different hemifields, settings indicated no change in the tilt of the grating. In Experiment III, where the fixation area was again midway between grating and setting line, but where the grating was replaced by a single line after the adaptation period, settings indicated that the line had decreased in apparent tilt. The results of the three experiments indicate that while gratings either do not normalize or do so to an insignificant extent they produce a substantial amount of normalization on a single line. Comparison of the results of Experiments I and II shows that spread of this effect outside the directly adapted area is less across the naso-temporal division of the retina than within the same hemifield.Department of Psychology, University of Aberdeen, Kings College, Old Aberdeen AB9 2UB.
It was found that brief periods of exposure to visual rearrangement elicit aftereffects that are still of considerable magnitude 24 h later. Despite the existence of these after-effects, visuomotor coordination does not appear to be disrupted between test periods, suggesting that these after-effects may be similar to some of the recently described situation-dependent visual after-effects.
An experiment is reported which shows the effect of inspection of a curved line on the apparent curvature of a curved test line for a range of curvatures of both I and T lines. A second experiment extends the range of I curvatures, using only one T line, a straight line. The experiments showed both adaptation and repulsion components in the FAE.
An experiment by Kohler and Wallach which could not be reconciled with these results was repeated in the relevant part; the results were in agreement with the first experiment here and did not agree with those obtained by Kohler and Wallach.
An argument is presented that both adaptation and repulsion effects could be produced by a cell adaptation mechanism.
The relative contributions of proprioceptive and efferent information in eliciting adaptation to visual rearrangement were studied under two conditions of visual stimulation. Subjects permitted sight of their forearm under normal room illumination showed significant adaptation when the forearm was (a) moved up and down under the action of tonic vibration reflexes, (b) voluntarily moved through the same trajectory at the same pace, (c) viewed while still, and (d) viewed while the margins of the elbow were vibrated. The reflex movement condition elicited significantly greater adaptation than the other conditions. Subjects allowed only sight of a point source of light attached to their hand showed significant adaptation when the forearm was (a) reflexly moved, (b) voluntarily moved through the same trajectory at the same rate, (c) passively moved, (d) still, and (e) vibrated while still. Less adaptation occurred as the amount of proprioceptive information about limb position was decreased. The adaptation elicited by voluntary movements of the forearm and by reflex movements did not differ significantly. It is concluded that corollary-discharge signals may not be crucial in adaptation to visual rearrangement; a more important factor appears to be discordance between proprioceptive and visual information.
Data recently presented by Wilson (1965) seem to demonstrate the separate effects of adaptation and of after-effect repulsion during and following continued observation of a curved line. Inasmuch as the experiment was performed without apparent reference to the psychophysical theory of figural after-effects (Taylor, 1962), it is interesting to note that the results on adaptation agree qualitatively with one of the major presuppositions of the theory, and the results on repulsion agree quantitatively with its predictions.
Human subjects were asked to identify one of seven possible luminance levels under Ganzfeld conditions. The luminance range investigated was 0.5–500.0 ft 1m. Earlier findings on the subjective effects of a Ganzfeld on humans were verified. Subjects performed significantly better under non-adapted than under adapted conditions. Under both conditions subjects tended to perform better after pupillary diameter had been fixed. Errors never exceeded 1 log10 unit in magnitude.
Subjects were exposed to a prismatically displaced view of their actively-moved right hand which was optically “stopped”; they achieved as much adaptation in this condition as in one in which they were allowed full “reafferent” stimulation. This provides further evidence against Held's “reafference“ hypothesis.Present address: Department of Psychology, University of Reading.The above experiment was carried out at the Department of Psychology, University of Bristol, while I was in receipt of an S.R.C. studentship. I wish to thank Dr Stuart Anstis, of Bristol, and Dr Brian Craske, of Southampton, for valuable discussion, advice, and encouragement; and Mr Hadyn Ellis of Reading for his criticism of the manuscript.
The results of previous studies of intermanual transfer of prism adaptation may have been biased because the arm was mobile during training, rather than for instance the head. It was hypothesized that adaptation will be more associated with a joint when it is mobile rather than stationary. Intermanual transfer when arm was mobile and head stationary was compared with that when head was mobile and arm stationary. Also measured was the adaptation persisting when the mobile part in training was stationary in testing. The results showed, against the original hypothesis, that adaptation tends to be associated with a stationary joint. This fits in with evidence that there is greater position uncertainty in a stationary joint and that this is associated with adaptability.
In Experiment I subjects pointed repeatedly at a target viewed through laterally displacing prisms and received terminal visual feedback. In one task the pointing movements were slow (proprioceptively controlled), and in the other they were fast (pre-programmed). In both tasks adaptation proceeded at the same rate and to the same level of performance. Following fast pointing with prisms a large amount of arm-body adaptation was found with slow and fast test movements, while following slow pointing with prisms a large amount of arm-body adaptation was found with slow test movements, but only a small amount with fast test movements. The result suggests that adapted behaviour with preprogrammed movements is not mediated by a proprioceptive change. In Experiment II pointing movements were passive. No arm-body adaptation was found with fast test movements, and, contrary to expectation, only a small amount with slow test movements.
Three experiments were performed to evaluate the influence of active and passive limb movements on adaptation to visual displacement. Over a wide frequency range (0·5-1·25 Hz) with constant amplitude, 30°, significant adaptation was achieved with active and passive movements. When arm movement frequency was constant at 1·0 Hz but amplitude of movement was varied, less adaptation was achieved for both active and passive movements than when amplitude was held constant. Even at a frequency above that of most naturally occurring limb movements, 1·67 Hz, and with variable amplitude motion, significant adaptation was achieved with active and passive limb movements. These findings emphasize the importance of visual-proprioceptive discordances for adaptation to visual displacement when only sight of the hand is permitted. Significant differences did not appear between the active and passive movement conditions in any of the experiments.
Subjects inspected their feet via base-out prisms for 3 min. Using binocular vision, subsequent reaching without prisms showed significant overestimation of distance. Monocular testing showed a lateral shift in pointing to targets in opposite directions for each eye. This indicates that registered, as opposed to actual, convergence is a factor in near distance perception, and that opposite adaptation occurs within the motor control system for each eye.
The work of Sternberg (1969) suggests the independence from one another of the times required for encoding a stimulus, matching it against a set of stored representations in memory and responding. A card sorting experiment was performed to test some implications of this position. The variables manipulated were the number of different letters to be sorted into a pile, orientation of the letter on a card, and whether letters encodable according to a shared physical characteristic were to be sorted into the same (within) or different (between) piles. As predicted, orientation of the letter and number of different letters to be sorted/pile affected sorting time only in the between pile condition where the effects were observed to be additive.
In Experiment I, the visual tilt illusion induced by two orthogonal lines was found to differ from the sum of the illusions induced by each line independently. The length of one of the orthogonal-inducing lines was varied in Experiment II with the other inducing line remaining a fixed length. As length increased from zero (no line) to 100%, the size of the illusion increased monotonically. The increase in illusion was not due to the increasing length of the variable line alone since, in the absence of the line of fixed length, increasing the length of the variable line produced no significant trend in the illusion (Experiment III).
The phenomenon of non-additivity of cues has been shown to exist in the learning of various types of discriminations by rats (Sutherland and Mackintosh, 1964; Sutherland and Holgate, 1966). In the present study severely subnormal children were trained to discriminate stimuli differing along two dimensions, both dimensions being relevant to the discrimination. Having learned to criterion they were then transfer-tested on each of the dimensions presented separately. Results showed both that subjects tended to respond in terms of dimensions and also that slow learners tended to learn the discrimination in terms of only one dimension whereas faster learners tended to learn about both dimensions. In a further study it was found that the more difficult the discrimination to be made the more the subjects tended to learn it in terms of only one of the two possible relevant dimensions. Some varying interpretations of the concepts of attention and capacity and their value and precision in explaining these results are considered.Present address: Goldsmiths' College, New Cross, London S.E. 14.
An adjacency effect was demonstrated at a high level of significance in the free recall, by 123 subjects, of a list of 40 high-frequency nouns presented in varying order on successive trials. The phenomenon referred to as the adjacency effect consists of the fact that when a subject is given repeated trials of study and free recall of a list of words (always presented in a different order), the probability of recalling a given item is greater when the item is presented temporally adjacent to an item which is already learned (as evidenced by recall on the previous trial) than when the item stands temporally between other items which are not yet learned. The enhancement of recall is greater when the item is presented between two previously learned items. The implications of the adjacency effect for verbal learning theory, particularly for the serial-position effect in serial learning and the concepts of interference and neural consolidation, are discussed.
Intermittent delivery of food pellets induces high levels of adjunctive drinking in rats, a pattern of behaviour which some have suggested is due to emotional arousal. In this experiment, however, chronic administration of a dose of chlordiazepoxide, a minor tranquillizer, did not prevent the development of adjunctive drinking after food pellets delivered at 1-min intervals. Indeed, the drug was found slightly to enhance the development of drinking, an effect assumed to be due to the drug's ability to facilitate the performance of several patterns of responding. When chlordiazepoxide was withdrawn a disruption in the pattern of adjunctive drinking was observed.
Sixteen male alcoholics were shown pairs of light flashes separated by intervals ranging from 0 to 100 msec., and judged whether there were one or two flashes. Two-flash fusion theshold (TFT) was raised by administration of promazine hydrochloride, a tranquilizing drug, and was higher for strict than for lenient instructions. Signal detection analysis showed that the drug reduced sensitivity but did not affect criterion, while instructions altered criterion placement without changing sensitivity.Present address: Birkbeck College, University of London.Present address: McGill University, Montreal, Quebec, Canada.
Chlorpromazine (0.5–3.0 mg/kg) significantly reduced orienting to a novel auditory stimulus, but subsequent habituation after repeated presentations of the stimulus was not prevented nor significantly impaired. These results support the suggestion that the mechanisms underlying orienting and habituation are independent.