Psychophysical methods are the tools for measuring perception and performance. These tools are used to exhibit basic perceptual processes, to analyze observer performance, and to specify the required characteristics of a display. Psychophysical measurement is often defined as a measurement of behaviour to highlight internal processes. The experimenter typically does not surround his/her focus in the actual behaviour, which could be as simple as ‘pressing a button’.
“an exact science of the fundamental relations of dependency between body and mind” (Fechner, 1860). Average sentence length 15-20 words
Psychophysical Methodologies
Psychophysics sets out a range of main methods to measure sensory thresholds. This is known as ‘Absolute threshold’ which scales out to see the smallest stimulus intensity that can be perceived. You then also have ‘Difference threshold’, to look at which of the two stimuli that can be perceived is smaller. When methods such as these are conducted they would be constructed to the individual in the description of ‘How intense’, ‘beautiful’, ‘likable’ is this object / thing. It objectively aims to demonstrate physical properties of the external world to a person’s experience of it. These are viewed as the link between external world and the inner world experiences. This depicts clearly the methods that are directed at painting an accurate depiction of the sensory capabilities. Green (1993b) has developed a maximum likelihood technique by which a stimulus dimension can be sampled with high efficiency and that yields valid threshold estimates in as few as a dozen trials, using a yes-no (single-interval) procedure. This method appears to have promise for studies of large stimulus domains in which stimuli yield.
Preferential Looking/Vision
By placing the psychophysical techniques in the context of a forced-choice psychophysical procedure, it allows behaviour to be examined from a quantified perspective (Teller, Morse, Borton, & Regal, 1974; Peeples & Teller, 1975; Regal, Boothe, Teller & Sackett, 1976). This technique follows Fantz’s (1965, 1967) preferential looking (PL) technique, combined with a forced-choice approach to data collection (Blackwell, 1953; Bush, Galanter and Luce, 1963). The variant of the PL technique may be called forced-choice preferential looking (FPL). An infant is held facing a stimulus display (Teller et al., I974). A visual stimulus, such as an acuity grating, is presented in one of two possible positions, left or right, on each of a series of trials. The surrounding visual field is a medium grey, chosen to match the acuity grating in average luminance. Thus, if the stripes are fine enough to be invisible to the infant, the acuity grating will match the screen in brightness and the infant will have nothing to see. On the other hand, if the stimulus is visible and attractive, the infant will usually stare in the direction of the stimulus. As in Fantz’s technique, an adult observer is located behind a peephole at the center of the screen. The observer’s task is to use the infant’s eye and head movements, and staring patterns, to infer or guess the location of the stimulus.
Auditory/ Speech Perception
Auditory psychophysics or psychoacoustics has been concerned with measures of absolute sensitivity, masking, and discrimination between sounds. These can differ in frequency content, intensity, duration, and spatial location. Other studies have compared different identification tasks, such as binary classification, numerical rating scales, absolute identification, and perceptual distance scaling (e.g., Ganong & Zatorre, 1980; Massaro & Cohen, 1983b; Vinegrad, 1972). The psychophysical methods applied in the study of speech perception are essentially the same as those applied in research on auditory, visual, or tactile perception of non-speech stimuli. Indeed, the generality across different stimulus domains and modalities of Weber\’s law or the law of temporal summation has been an important discovery. Such laws are in accordance with behaviourist and information-processing orientations in psychology, which assume that perception and cognition are governed by general-purpose, domain-independent processes. The description of such processes is an important part of psychological research. Measurement of the absolute hearing threshold provides some basic information about our auditory system.
Auditory perception skills in infancy have been shown to be predictive of language outcome at 3 years of age (Benasich & Tallal, 2002). However, it is essential to investigate concurrent associations between auditory processing skills and language in the early school years. A study was designed to compare frequency discrimination abilities for forward and backward masking tasks in children aged 5-7 years and to investigate the relationship between auditory processing skills and language. Based on Sutcliffe and Bishop (2005), it was hypothesised that children’s frequency discrimination thresholds would be lower for forward masking than for backward masking. It was also hypothesised that children with etter (lower) frequency discrimination thresholds would score higher on a language assessment than those with poorer (higher) frequency discrimination thresholds. The role of nonverbal ability in auditory processing has been investigated in only a few studies, with inconsistent findings. McArthur and Bishop (2004b), for example, found non-significant differences on nonverbal IQ between groups with poor and good frequency discrimination. In contrast, Deary (1994) found a small but significant relationship between frequency discrimination and both verbal and nonverbal performance scores.
Infants vs. non-infants
Non-infants have also been shown to have excellent brightness discrimination capabilities and at least dichromatic color vision (Peeples & Teller, 1975), although their color vision may well be more limited than that of adults (Feller, Peeples, & Sekel, 1978). Infants respond to spatially sinusoidal striped patterns of various frequencies and contrasts, with the result that infant contrast sensitivity functions (CSF) can be explored (Atkinson, Braddick, & Braddick, 1974). Infant macaque monkeys can be tested with PL (Fantz, 1967) and FPL techniques. With FPL, newborn pigtail macaque monkeys demonstrate visual acuity closely resembling that of human newborns, and improve over the first few postnatal weeks in a fashion entirely comparable to the improvement shown by human infants over the first few postnatal months (Teller, Regal, Videen, & Pulos, 1978). These studies of normal development also provide an interesting context for visual deprivation studies (e.g.,von Noorden, 1973; Wiesel & Hubel, 1974; Regal, Boothe, Teller, & Sackett, 1976), and suggest that the critical or sensitive period during which the presence of visual stimulation is necessary for normal visual development coincides with the time during which acuity is emerging in the normally reared animal.
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