That I should be able, when looking at a plane surface limited by four lines making two acute and two obtuse angles, to see a square table-top is only explicable by remarking that this perception has been acquired just as most other habits have been, i. Nevertheless, we must suppose that for many weeks the perceptual process is on a very low level of advancement.
In the first place, as we pointed out, a perception involves our having some knowledge, however simple, about the object. But such knowledge about objects depends upon our ability to connect various sensory experiences with the same object, and this in turn depends largely upon our ability to control our movements. We mentioned in an earlier chapter that such control is a relatively late acquirement, and accordingly our perceptual processes get no available opportunity for development in early infancy.
An illustration will make this clearer. Let us take the possible course of events involved in a baby's acquiring the perception of a bell. Obviously the visual factors involved cannot be satisfactorily employed, until some control has been attained over the eye muscles, so that the child's eyes are able to converge and follow an object. This attainment is commonly achieved about the third or fourth week of life, although there is great variation here.
As a matter of fact, the bell will be put into his hand, and during the random movements of the hand his eye will sometimes fall upon it. The occasional repetition of this experience will soon serve to fix the association of the touch-band-movement feelings with the visual consciousness of the bell, so that the thing seen will inevitably suggest the thing felt and moved, and vice versa.
Moreover, all the time this has been going on there have been sensory stimulations of sound from the bell. This group of elements, therefore, becomes annexed to the. Such a case as this is typical, and despite certain omissions of detail, may serve to represent the kind of activities which always accompany the acquiring of perceptions.
It will be remembered that we connected the perceptual process with the establishment of relations. In the case which we have used for our illustration these relations show clearly in the connecting of one group of sensory experiences with another.
The auditory group comes to mean the eye group, and both of these come to mean the hand-movement group. Moreover, the definite establishment of these relations is practically dependent upon the motor factors by which the hand and eye come to control the object. When such relations as these are once set up, we have a definite perception of an object about which we know something, i.
It will be seen at once that in this series of events by which the perception becomes definite, the several steps involved are brought about on the strictly mental side by the action of attention, which we have previously sketched.
First, there is the dissociative process, throwing out into the foreground of consciousness the visual characteristics of the bell, as distinguished from other things in the visual field.
This is followed by the associative, or relating process, which connects this visual bell with the auditory and tactual-motor experiences. It remains, then, to inquire what further development takes place after the accomplishment of this synthesis of the different sensory activities of sound, sight, and touch into the consciousness of a single object. Development of Perception. If this metaphor were en-. Clearly, our reference to habit was in one particular misleading. Our most perfect habits are all but unconscious.
A perception, on the other hand, is distinctly a conscious process. The truth of our statement lies in this fact, i. We thus become almost wholly oblivious to the exact appearance of a doorknob which we have occasion to turn very often. Our eyes may rest upon it momentarily, but only long enough to guide the band in its movement, and often without registering any visual impression of which we could immediately afterward give an exact account.
There are also certain features of the neural process in perception which warrant our comparison with habit, and to these we shall come in a moment. The great mass of our perceptions, however, are of objects whose relations to us change sufficiently from time to time to make any complete subsidence of our consciousness of them incompatible with their effective manipulation; consequently we continue to be definitely aware of them.
The development of perception, which goes on in a certain sense more or less all our lives, and in a very definite sense up to the period of mental maturity, is plainly not a development involving simply a more automatic response to objects.
Quite the contrary. The process which we commonly think of as growth in the powers of perception consists in the further elaboration of the discriminative and associative activities of attention. We learn to see Dew things in the old objects, new charactertistics, sic which before escaped our knowledge. We also learn more about the objects, and thus, when we perceive them, perceive them in a modified and more intelligent way. Speaking literally, it therefore appears that.
A moment's reflection will show the similarity of this fact to one which we noted when analysing attention, i. We might of course substitute the word perception for the word attention, inasmuch as attention is an attribute of all consciousness, and then the proposition would read: we can not continue to perceive an object beyond a moment or two, unless we perceive it in a new manner. Perceptions which we do not execute in a new way we have already seen do actually tend to lapse from consciousness, passing over into habits of response which we make to certain physical stimuli.
When a child is taught to observe the arrangement of the petals in a flower, he thenceforth perceives the flower in a new way. To him it really is a new object. All development in perception is of this kind, and constitutes a sort of transformation by the unfolding of the old object into the new and richer one. The larger part of this perceptual development occurs during childhood and adolescence.
Nevertheless, there is a continuation of the process in an inconspicuous way far into old age. Thus, we come in childhood to recognise the salient characteristics of the common things about us in every day life. During adolescence we enrich this material by observing more accurately the details of these things, and by increasing our knowledge of their general purport and relations. After attaining maturity our further advance is almost wholly connected with the affairs of our professional, or business, life.
The musician becomes more sensitive to the niceties of harmonic accord and the nuances of melodic sequence. The business man becomes more observant of the things which pass under his eye, so far as they are related to his specialty. The elementary school teacher learns how to keep the corner of her eye sensitive to iniquity upon the back. The mother learns to watch her children with an increasingly intelligent discrimination between acts which indicate illness and those which indicate fatigue, excitement, and transitory irritation.
Everywhere development is primarily shown by fresh skill in the detec. An illusion is a false, or erroneous, perception, which is often spoken of as a deception of the senses. But this is misleading, as we shall presently see, for the senses ordinarily operate properly enough.
The difficulty is with our reaction upon the sensory material furnished to us. Among the most frequent of such illusions is the misreading of printed words.
We sometimes read the words put before us as we have reason to suppose they ought to be, not as they are. Thus, if we come across the word mispirnt, many of us will read it in all good faith as misprint and never see the difference. We react to the general visual impression and its suggestion, and see what really is not before us. If the sentence in which the word occurs is such as to give us a definite anticipation of the word, the probability of our overlooking the typographical error is much increased.
Similarly when we come into a darkened room where sits a spectral form-an experience which as children most of us have hadwe see a person with startling clearness; and the subsequent discovery, that the supposed person consists of clothing hanging upon a chair, is hard to accept as true.
Illusions of sound are very common. We fancy we hear our names called, when in point of fact the sound we thus interpret may have been anything from a summons to some other person of similar name, to the barking of a dog, or the whistle of a locomotive.
Tactual illusions are also easy to produce. The so-called "illusion of Aristotle " is a good specimen. Children often achieve it by crossing the first and second fingers, and then moving to and fro upon the bridge of the nose with the crotch thus formed between the fingers.
Presently one becomes distressingly impressed with the fact that one possesses two noses. This last instance is typical of many illusions, in that it is caused by stimulating with a single object the sides of the two fingers which are not ordinarily in contact with one another, and for the stimulation of which, accordingly, two objects are commonly necessary.
We react in the familiar, the habitual, way to the simultaneous stimulation of these areas of the skin. This has invariably been accomplished hitherto by the pressure of two objects, and two objects we therefore feel eel. It is clear that in such a case the sense organ is in no way at fault.
It sends in the impulses communicated to it just as it has always done before; but the reaction which we make upon the impression also follows the usual course, and in this special case happens consequently to be wrong. The same explanation applies to our reading of incorrectly spelled words. Many illusions of movement, e. The same general principle holds, but applied in a slightly different manner, when we see, or hear, or otherwise perceive, some object not actually present, because we are expecting to perceive it.
Thus, if we are listening for expected footsteps, we find ourselves time after time interpreting other sounds as those of the awaited step. At night the nervous housewife wakens to hear the burglars passing from room to room along the corridor. Step follows step in stealthy but unmistakable rhythm, though the whole impression has no other objective basis than the occasional cracking of floors.
There are many kinds of illusions, be it said, which do not come immediately under the headings we have discussed. For example, such illusions as that in figure 51 are much too complex in their basis to be properly included, without modification, under the explanatory rubrics we have considered.
It is clear that a consideration of illusion affords new and striking confirmation of the part played in perception by previous experience. The cortical reaction suggested by the. But this cortical reaction is evidently determined ,by the impress of old perceptual experiences whose traces have been preserved. The same point is admirably illustrated :by such drawings as the accompanying, figures 52 and We can see the stairs, either as they appear from above, or from below. In one case the surface a seems nearer to us; in the other case b seems nearer.
We can see in the other figure a big picture frame, the frustrum of a pyramid, or the entrance to a square tunnel. See percept , -ion. Words nearby perception percentile , percent sign , per centum , percept , perceptible , perception , perceptive , perceptual , perceptual defence , perceptual mapping , Perceval.
Words related to perception approach , attention , attitude , awareness , concept , consciousness , feeling , image , impression , judgment , knowledge , notion , opinion , recognition , sense , taste , thought , viewpoint , acumen , apprehension. How to use perception in a sentence Bourla acknowledged that the late October date, coming right before the election, created the perception of political involvement, which could undermine confidence in the vaccine.
Children's Ways James Sully. A Letter from Mr. Cibber to Mr. Pope Colley Cibber. Napoleon's Marshals R. Derived forms of perception perceptional , adjective. The results in all conditions indicated that a high positive schizotypy score was associated with an increased tendency to perceive complex meaning in images comprised purely of random visual noise. Our results suggest that differences in perceptual performance for individuals high in positive schizotypy are not related to increased suggestibility or susceptibility to instruction, as had previously been suggested.
Instead, the observed reductions in sensitivity along with increased response bias toward seeing something that is not there, indirectly implicated subtle neurophysiological differences associated with the personality dimension of schizotypy, that are theoretically pertinent to the continuum of schizophrenia and hallucination-proneness.
Editor: Michael H. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data are within the paper and its Supporting Information files. Competing interests: The authors have declared that no competing interests exist. Like all human abilities and traits, there are individual differences in visual perception.
Anecdotally, these can lead to seeing different things in a cloud-filled sky and appreciating particular forms of abstract art [ 1 ].
Experimentally, these variations range from slight, and perhaps random, fluctuations in performance across individuals [ 2 — 5 ], to considerable dissimilarities that can be reliably traced to broader group differences in, for example, gender [ 6 ], personality [ 7 ], culture [ 8 ], motivation [ 9 ], and the spectrum of psychosis [ 10 , 11 ]. In the work described here we use the commonplace observation of meaningful images in the clouds to construct stimuli that allow us to measure individual differences in the inclination to see something in a degraded, noisy stimulus when nothing is actually there.
The visual system is predisposed to extract meaning, often from stimuli containing substantial amounts of uncertainty; indeed one could argue that is its primary role.
The meaning that is imposed can depend on our internal templates of prototypical stimuli [ 12 , 13 ] our expectations and learned probabilities about the visual environment [ 9 , 14 — 20 ], contextual cues or prior visual input [ 21 , 22 ] and on random neural fluctuations in functionally relevant areas of cortex [ 23 — 26 ].
Each of these processes are also subject to influence by other factors such as the personality or factors which influence personality of the individual. For instance, when subjects were presented with a sequence of line-drawings, starting with an extremely degraded image that gradually became less degraded as the sequence progressed, and asked to respond once they could identify the image, those who responded earlier in the sequence, although less accurately, were those with stronger beliefs in paranormal phenomena [ 27 ].
Overall, the results imply an influence of the internal state of the system in this case a particular belief system on the outcome of the process of construction of meaning, with a role for both of expectations [ 9 , 14 — 20 ] and prototypical templates [ 12 , 13 ]. From a more generalised perspective, psychometric scales of personality have long been thought to influence aspects of perception which, in turn, influences behaviour [ 32 ]. Belief in extra-sensory perception and paranormal phenomena, and high scores on measures of psychoticism and magical thinking can be contextualised in terms of the personality dimension of schizotypy [ 31 , 33 ].
The concept of schizotypy has often been employed within a dimensional approach to psychosis, whereby psychopathological symptoms are thought to form a quantitative continuum with normal, healthy traits [ 34 — 36 ].
The presence of schizotypal traits, even at relatively high levels, does not imply impaired functioning [ 37 ], but may be indicative of risk for psychosis-spectrum disorders [ 38 , 39 ]. Of particular interest for the present research is what has been termed the positive-psychotic subtype, which encompasses distorted or intense subjective sensory experiences and minor manifestations of delusional beliefs.
Experimentally, when observers were presented with a random array of white dots on a black background and misleadingly instructed that the dots sometimes show something meaningful, individuals who score higher on questionnaire measures of psychoticism, neuroticism, and hallucination-proneness are more likely to report perceiving meaningful images of a complex nature in the dots [ 45 ].
Such complex false alarms on this Random Dots Task RDT have also been associated with belief in extra-sensory perception [ 46 ], magical thinking and positive schizotypy [ 47 ].
Individuals high in positive schizotypy also see more words in a dynamic string of non-word strings than low-scoring individuals [ 48 ], mirroring the result from similar work with paranormal believers [ 31 ]. This effect is strengthened when the frequency of real words is increased [ 18 ], and is mediated by expectation, even when that expectation is not met [ 16 ].
These data are consistent with perceptual biases that predispose those high in positive-psychotic traits to have measurable false perceptions.
The overall aim of this work is to use the visual false alarm in this context to examine how personality interacts with perception. From a task-driven perspective, while much previous work used artificial stimuli and subjective judgements open to suggestibility [ 58 , 59 ], the two experiments presented here outline the development and use of a more ecologically valid and controlled visual stimulus in a signal-detection task paradigm, allowing us to more confidently attribute performance to perceptual differences between individuals see also [ 28 , 31 , 48 ].
Consideration of the statistical properties of natural scenes has been fruitful for understanding the way the visual system works [ 62 — 65 ]. To distinguish the task we refer to it as the Perception of Meaning task or POM where the use of an acronym does not compromise readability. Consistent with the literature reviewed above, we suggest that positive-psychotic personality traits as measured by the Unusual Experiences sub-scale of the Schizotypy metric mediate the occurrence of visual false alarms, and that using ecologically valid stimuli in an appropriately controlled psychophysical paradigm will enable this to be measured more effectively in a normal population.
We expect that those individuals which score highly on Unusual Experiences will experience more visual false alarms and that our paradigm will allow us to discriminate between sensitivity and bias in the subjects, as well as removing any influence of suggestibility on the data. Two experiments will be reported here, both examine the interaction between personality and perception.
Common aspects of the methodology with be described in this section, with the complementary specifics at the head of each Experiment.
None of the participants in Experiment 2 had taken part in Experiment 1. Both studies were approved by the Human Ethics Advisory Group at the University of Melbourne and each participant provided written consent for participation and publication of their anonymous data. The VVIQ is a item questionnaire that asks respondents to mentally conjure and rate the vividness of features in four visual scenes the face of a friend, the rising sun, a familiar shop-front, and a country scene.
During this portion of the procedure, subjects were free to close their eyes, or keep them open; most subjects closed their eyes see note in Experiment 1 , discussion. The GSIS is an interview-style measure where respondents are read a short vignette and are then asked 20 questions relating to the story, 15 of which are leading questions regarding information that was never provided. Regardless of their accuracy, respondents are firmly told they have made a number of errors and asked the same questions again, with instructions to try and be more accurate.
Responses are scored on the basis of accurate Recall 20 items and two aspects of suggestibility: Yield 15 items —the number of leading questions initially responded to in the leading direction, and Shift 15 items —the number of leading questions the respondent changed their answer to upon being asked the second time. IntAnh was omitted due to time constraints and because it was of least theoretical interest.
All image manipulation, coding, and presentation of experiments was carried out using the Matlab computer language [ 71 ] and the Psychophysics Toolbox [ 72 ]. All images were 8-bit monochrome greyscale, containing up to shades of grey, ranging from black to white. The effective pixel size spatial resolution was the same for each experiment and a property of the generation hardware, but the overall image size was restricted by the database used in each case Experiment 1 [ 73 ], Experiment 2 [ 74 ].
The voltage to luminance relationship of the display was approximately linear over the range used through the Apple standard gamma correction; this correction was considered adequate given the nature of the stimuli and task of the observer.
Later work presenting the images on a fully calibrated CRT display has yielded similar data [ 43 , 75 , 76 ]. Presentation took place in a darkened room with participants seated at a distance of mm from the screen supported with a chin-rest, such that one degree of visual angle corresponded to 64 screen pixels. Experimental sessions were conducted one-to-one and lasted approximately 90 minutes.
Monochrome pictures were combined with artificially generated two-dimensional noise to create visually degraded images. Experiment 2, however, in an important variation from Experiment 1, spatially degraded the image on an alternate pixel by pixel basis. This novel spatial degradation process meant that pre-specified proportions of image pixels were randomly designated as either signal or noise.
Thus, what was degraded was the degree to which the individual signal pixels correlate across space to generate a meaningful representation Experiment 2 , rather than the degree to which a single pixel in space is able to represent the signal Experiment 1.
The extent to which the visual system can discriminate between individual pixels and the precise signal to noise pixel structure will influence the effective difference between these two processes. This second method of image degradation has similarities to the phase-alignment method used recently by Hansen and colleagues [ 78 ]. A companion noise-only image was also created with the same mean and range of pixel values and the same RMS contrast. These were then combined to create a composite image where the noise was added to the signal pixel values and then normalised Experiment 1 , or a percentage of pixels were from the signal image and the remainder from the noise image Experiment 2 , again with the same RMS contrast to remove contrast as cue to the presence of an image.
A further noise-only image was also paired with each signal image as its non-signal counterpart. The image pairs were then band-pass filtered using a Fast Fourier Transform and Gaussian filter in Matlab in the spatial frequency domain to contain different octave bands of spatial frequencies, centred at 0.
This process is summarised in Fig 1a and 1b and experiment-specific details given below. Flow diagram representing the creation of the stimuli for the POM task used in Experiment 1 1a and Experiment 2 1b.
In this work we are interested in how different aspects of personality affect performance on the psychophysical tasks. As outlined in the introduction we have the most theoretical interest in the positive dimension UnEx and CogDis in the O-LIFE , although we did examine all dimensions at the outset, and where possible we examined and included all dimensions of the O-LIFE, despite being aware of differing views as to the relevance of all four [ 40 , 41 ].
We also analyse and present the data in a way consistent with our theoretical approach to the study; that personality is related to psychophysical performance in our particular task.
Furthermore, we analyse the data both from a continuous and dichotomous perspective to facilitate comparison with previous work [ 16 , 45 ]. In order to designate respondents as low or high on a given schizotypal dimension a median-split was computed on the scores in order to compare our results to previous work. We are mindful of the potential issues of conducting a median split on continuous data e. We examined the data in all regression analyses for multi-collinearity and in no instance was the variance inflation factor VIF greater than 2 or the tolerance less than 0.
We have chosen to report both the continuous and dichotomous results in most cases. Missing data was accounted for on an analysis-by-analysis basis, which accounts for minor variations in subject number n in some analyses. Finally, we provide the Bayesian statistical analysis of the critical data as Supporting Information S1 Appendix. Similar instructions were given for completing both tasks, with participants told that they would be seeing a number of images, some of which contained something meaningful, and to describe out loud what they saw if and when they saw something meaningful or recognisable.
Each image appeared on screen for 6 seconds before automatically changing to the next, for a total presentation time of approximately 18 minutes stimuli in total. The order of images was randomised so each subject saw them in a different sequence. The experimenter sat about 2 metres behind the participant and recorded their responses verbatim, while remaining as unobtrusive as possible.
Eight photographs of natural scenes e. Paired with the noise stimuli and band-pass filtered to 6 different spatial frequency brackets, the final stimulus set therefore comprised 90 signal and 90 noise stimuli see Fig 1a , which were randomly intermixed prior to presentation such that no two participants viewed them in the same order. They were presented in a single block of images. Stimuli for the RDT were created by generating 60 random arrays of dots filling a space the same size as the images of the POM.
Detailed responses to the RDT e. These criteria were also used to classify false alarm responses to the POM. In addition, misinterpreted responses to the POM signal stimuli that were incorrect and greatly removed from their actual content e. There were no images embedded in the RDT, so no hits or misses per se could be recorded although, arguably, a null response could be classified as a hit or a miss in this case. This methodology differs from traditional signal detection methods where false alarm rates are calculated as the total number of false alarms divided by the total number of noise stimuli only.
As such, the conventional rules of signal detection theory where the hit rate is equal to 1 minus the miss rate, and the false alarm rate is equal to 1 minus the correct rejection rate do not strictly apply to this data, although the relationships are a fairly close approximation. Scores on the questionnaire measures are summarised in Table 1 , and are all comparable to reported norms for these psychometrics [ 69 , 70 , 84 , 85 ]. Scores on the IntAnh subscale of the O-LIFE were positively skewed and so square root transformations were computed to correct for this, and the transformed scores were used in all parametric analyses.
The mean hit rate for the POM was Square root transformations were required to correct for positive skew for the complex and simple false alarm rates on both the RDT and the POM. The correlations between the personality measures and performance on the two visual tasks are presented in Table 2 , which indicates that positive-psychotic schizotypy as measured by UnEx scores was the only measure to be consistently associated with performance.
This was reflected in the Bayesian correlation see S1 Appendix with a moderately high Bayes factor of Four blockwise hierarchical linear regression analyses, predicting the complex and simple false alarm rates on the RDT and the POM , were conducted. UnEx scores were entered in the first step, and the remaining schizotypy measures, suggestibility scores, and visual imagery scores were entered blockwise in the second step. This established whether these measures contributed to predicting false alarm rates once the effects of positive-psychotic schizotypy had been accounted for.
None of the other personality measures made a significant contribution to predicting simple response rates on the RDT once the effects of UnEx had been accounted for.
The addition of the remaining personality variables did not result in a statistically significant increase to the variance already accounted for by UnEx , either for complex or simple false alarm rates on the POM. It should be noted, however, that CogDis scores did make a significant contribution to predicting complex false alarm rates in the second step of the regression, with POM false alarm rates decreasing as CogDis scores increased.
This is an unexpected result, but may possibly be related to social anxiety and neuroticism, which is reflected in an increasing CogDis score [ 86 ]; if this increase in anxiety causes the subjects to moderate they complex FA responses, for fear of seeming odd.
We thank one of our reviewers O. However, we note that one potential limitation of Experiment 1 was that we did not control whether participants completed the imagery task with open or closed eyes. It is possible that those completing it with closed eyes may have obtained higher VVIQ scores, which may have contaminated the effects of any association between imagery and schizotypy scores, or scores on the POM.
On the RDT , however, suggestibility also played a role, with those participants who were more likely to alter their responses due to experimenter instruction indexed by the GSIS Shift scores also more likely to report false alarms. Suggestibility did not impact performance on the POM. This coupled with the absence of any misleading experimenter instructions, as well as the more sophisticated and naturalistic characteristics of the noise stimuli, indicate the POM to be a promising tool for measuring hallucination proneness in laboratory settings with good discriminant and construct validity.
The high UnEx group made significantly more false alarms than the low scorers. Details are presented in the Supporting Information S1 Appendix but the result is summarised in Fig 2. Ultimately this is the same result as the regression above, and based on the same hierarchical linear model, but presented in a more digestible format. The final analysis was concerned with investigating the effect of positive-psychotic schizotypy on the complex false alarm rates on the POM across the different spatial frequency bands.
Post-hoc comparisons revealed the differences between the low and high UnEx groups to be significant at 0. Lower frequency bands elicited more false alarms than higher ones, an effect that was exaggerated for individuals high on UnEx.
There is some evidence that low spatial frequencies are processed more rapidly than higher ones [ 87 ], although this will likely depend upon the precise task at hand. In addition, according to some theories e. We speculate that this earlier response might therefore be exaggerated with low spatial frequency information. Overall, the results of Experiment 1 showed that the noise-based POM stimuli amplified the effect originally seen for the dot RDT stimuli [ 45 ]; whereby a high UnEx O-LIFE score was correlated to the likelihood of seeing a meaningful image when there was nothing present.
This validates our contention that a more ecologically valid stimulus increases individual differences in the imposition of meaning. The second experiment extends this result to examine the same effect in a signal detection framework. The importance of accuracy and speed were both emphasised, and reaction times were recorded.
It should be noted that responses were made on a laptop with an integrated keyboard so the losses in reaction time accuracy associated with a peripheral USB keyboard were avoided.
The reaction times were also in accord with those of another study, measured using separate and calibrated button boxes RTBox and a Cedrus box [ 43 , 76 ]. The practice block of the POM was administered first, during which accurate audible feedback was provided. Each stimulus trial commenced with a blank screen prompting participants to press the spacebar, a fixation cross on a black screen of mean luminance then appeared for ms.
An audible beep signalled the onset of the stimulus, which was presented for exactly ms rectangular temporal envelope , followed by another blank screen.
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