Unit II. Psychophysics

Task 1. Choose the best answers to the questions:

1) What is psychophysics?

1. science

2. art

3. hobby

2) What disciplines intersect in psychophysics?

1. sociology and physics

2. philosophy and math

3. psychology and physics

3) Who was the founder of psychophysics?

1. Vladimir Lenin

2. Barrack Obama

3. Gustav Fechner

Task 2. Read and translate the text “Psychophysics”:

Many of the classical techniques and theory of psychophysics were formulated in 1860 when Gustav Theodor Fechner published Elements of Psychophysics. He coined the term “psychophysics”, and described research relating physical stimuli with how they are perceived and set out the philosophical foundations of the field. Fechner wanted to develop a theory that could relate matter to the mind, by describing the relationship between the world and the way it is perceived. Fechner’s work formed the basis of psychology as a science.

Psychophysicists usually employ experimental stimuli that can be objectively measured, such as pure tones varying in intensity, or lights varying in luminance. All the senses have been studied: vision, hearing, touch (including skin and enteric perception), taste, smell, and the sense of time. Regardless of the sensory domain, there are three main topics in the psychophysical classification scheme: absolute thresholds, discrimination thresholds, and scaling.

The most common use of psychophysics is in producing scales of human experience of various aspects of physical stimuli. Take, for example, the physical stimulus of sound frequency. A sound frequency is measured in hertz, cycles per second. But human experience of this phenomenon is not the same as the frequencies. For one thing, there is a frequency below which no sound can be heard, no matter how intense it is (around 20 Hz depending on the individual) and there is a frequency above which no sound can be heard (around 20,000 Hz, again depending on the individual). For another, doubling the sound frequency (e.g., from 100 Hz to 200 Hz) does not lead to a doubling of experience. The perceptual experience of the sound frequency is called pitch, and it is measured in mels.

More analytical approaches allow the use of psychophysical methods to study neurophysiological properties and sensory processing mechanisms. This is of particular importance in human research, where other, more invasive, methods are not used due to ethical reasons.

Areas of investigation include sensory thresholds, methods of sensitivity measurement, and signal detection theory.

A threshold (or limen), is the point of intensity at which the participant can just detect the presence of, or difference in, a stimulus. Stimuli with intensities below the threshold are considered not detectable, however stimuli at values close to threshold will often be detectable of some proportion of the time. There are two kinds of thresholds: absolute and discrimination.

An absolute threshold is the level of intensity of a stimulus at which the subject is able to detect the presence of the stimulus. An example of an absolute threshold is the number of hair on the back of one’s hand that must be touched before it can be felt – a participant may be unable to feel a single hair being touched, but can feel two or three as this exceeds the threshold.

A discrimination threshold is the magnitude of the difference between two stimuli of different intensities which the participant is able to detect. To test this threshold, several methods are used. The subject may be asked to adjust one stimulus until it is perceived the same as the other, may be asked to describe the magnitude of the difference between two stimuli, or to detect a stimulus against a background.

Absolute and discrimination thresholds are sometimes considered similar because there is always background noise interfering with our ability to detect stimuli, however study of discrimination thresholds still occurs, for example, in pitch discrimination tasks.

In discrimination experiments, the experimenter seeks to determine at what point the difference between two stimuli, such as two weights or sounds, is detectable. The subject is presented with one stimulus, for example, a weight, and is asked to say whether another weight is heavier or lighter. At the point of subjective equality, the subject perceives the two weights to be the same. The just noticeable difference is the difference in stimuli that the subject notices.

In psychophysics, experiments seek to determine whether the subject can detect a stimulus, identify it, differentiate between it and another stimulus, and to describe the magnitude or nature of this difference (from http://en.wikipedia.org).

Task 3. Translate the words from English into Russian:

1) technique; 2) to relate; 3) touch; 4) discrimination threshold; 5) intense; 6) approach; 7) to detect; 8) to exceed; 9) to adjust; 10) to determine; 11) subjective equality.

Task 4. In the text “Psychophysics” find English equivalents to the following Russian words and word combinations:

1) стимул; 2) измерять; 3) абсолютная пороговая величина; 4) частота звука; 5) увеличение в два раза; 6) сенсорный; 7) участник; 8) величина; 9) вмешиваться, мешать; 10) узнать, распознать, идентифицировать.

Task 5. In the text find synonyms to the following words:

1) disturbing; 2) to describe; 3) to use; 4) field; 5) on the one hand … on the other hand; 6) definite; 7) to give.

Task 6. In the table match synonyms:

1. to coin	a. aggressive
2. to perceive	b. basis
3. foundation	c. difference
4. invasive	d. to create
5. discrimination	e. several
6. some	f. to feel

Task 7. In the text “Psychophysics” find antonyms to the following words:

1) subjectively; 2) unusual; 3) different; 4) above; 5) lighter; 6) few; 7) secondary; 8) absence; 9) after; 10) to be unable; 11) similar.

Task 8. Match the words and their definitions:

1. stimulus	a. the lowest level at which something begins to operate, happen, produce an effect, etc.
2. tone	b. the degree of highness or lowness of a musical sound or speaking voice
3. pitch	c. a person who takes part or has a share in an activity or event
4. threshold	d. something that causes activity
5. participant	e. the quality or character of a sound produced by a particular instrument or singing voice

Task 9. Form words of different parts of speech from the following verbs:

1) to formulate; 2) to publish; 3) to describe; 4) to perceive; 5) to employ; 6) to detect; 7) to discriminate; 8) to participate; 9) to experiment; 10) to produce; 11) to depend; 12) to investigate; 13) to measure; 14) to consider; 15) to differ; 16) to interfere; 17) to determine; 18) to notice; 19) to adjust.

Task 10. Translate the words in brackets into English to make the sentences complete. Pay attention to words from task nine:

1) Stop (вмешиваться) into my business. I’m an independent person. I’m not helpless. I can do everything myself.

2) Try (определить) the species of this butterfly.

3) Can you (отличить) a square and a rectangle?

4) A.I. Solzhenitsyn (считается) an outstanding writer, tribune and a man of freedom.

5) An ambiguous shadow (была замечена) in the window. A shot was heard and after that our director, Mr. Smith, fell dead. The (следователь) (уже сформулировал) a hypothesis. He thinks it was assassination.

6) Mr. White was lucky enough (участвовать) in the Queen’s interview and was the first among his competitors (опубликовать) it.

7) His grandmother wanted to insure her car through the Internet but she was afraid to do something wrong. Fortunately, the site had a very detailed (описание) how to do it properly.

8) This motorcycle, working on solar energy, exceeds the speed of 200 km/h. But it is not widely (производится) yet, it is only an (экспериментальная) model.

9) Eskimos can (различать) up to twenty types of snow and ice. And they have up to thirty words to denote them.

10) You should (приспособить, привести в соответствие) your personal working methods to your (работодателя) claims.

Task 11. Answer the questions:

1) When were the main methods of psychophysics described?

2) What is “The Elements of Psychophysics” about?

3) What are the stimuli used by psychophysicists?

4) What are three main domains of psychophysical classification?

5) What are the thresholds of human experience of the sound frequencies?

6) Are the invasive methods used on people?

7) What are the types of thresholds?

8) Can you give an example of an absolute threshold?

9) What are the methods to measure the discrimination threshold?

10) What does a discrimination experiment consist of?

Task 12. Say whether the statements are true or false. Correct false statements:

1) It was Gustav Fechner who first defined principles of psychophysics.

2) G. Fechner wished to show that there was some connection between love, music and poetry.

3) Psychophysicists study practically all senses: vision, hearing, touch, taste and behaviour.

4) A sound frequency is measured in mels.

5) Doubling of the sound frequency leads to doubling of human experience.

6) A threshold is a point of intensity at which the subject can say about presence or absence of a phenomenon.

7) A discrimination threshold is the magnitude of the difference between two stimuli of different intensities which a participant can detect.

8) The example of discrimination threshold is comparing two weights.

9) In psychophysical experiments, participant’s role is to detect a single stimulus.

Task 13. In the text find nouns which are Greek and Latin borrowings. Study the following words and put them into plural:

1) a stimulus; 2) a basis; 3) a formula; 4) a crisis; 5) a criterion; 6) an index; 7) a bacterium; 8) a phenomenon; 9) a datum; 10) an antenna; 11) a nucleus; 12) an apparatus; 13) an analysis; 14) a hypothesis.

Task 14. Translate the sentences into English. Pay attention to the Greek and Latin borrowings:

1) Относительно недавно ученые-физики смогли расщепить ядромолекулы. Теперь ядерная энергия широко используется в мирных целях.

2) Феномендетей-индиго занимает умы исследователей. Если раньше необычные способности проявлялись у взрослых людей, то теперь ими обладают маленькие дети.

3) Проведенный анализрынков показал, что все большее количество людей отдает предпочтение экологически чистым продуктам. Хотя цена на них и превышает цену обычных продуктов в несколько раз, спрос на продукты, произведенные без использования химикатов, возрастает. Не повлияет ли мировой экономическийкризисна эту тенденцию?

4) Несмотря на то, что человек считает себя властелином планеты Земля, на самом деле этот мир принадлежит бактериям, ведь они выживают как вне, так и внутри человеческих особей.

5) Критерииотбора претендентов на должность главного бухгалтера были очень строгими.

6) Великая теорема Ферма до сих пор остается загадкой. На первый взгляд формулапроста, но доказать ее правильность, как впрочем, и неправильность, не смог еще ни один ученый.

7) Основыстиля мудехар восходят к арабской традиции.

8) Гипотезао том, что снежный человек существует, подтверждается многочисленными свидетельствами очевидцев, однако представители фундаментальной науки не спешат делать однозначные выводы.

9) Первые лепетные слова ребенка, независимо от его национальной и языковой принадлежности, одинаковы. Артикуляционный аппаратребенка адаптируется к артикуляционным особенностямаппаратаокружающих его взрослых.

Task 15. Choose the best suitable word from the brackets:

Classic methods of experimentation

Psychophysical … (experiments, exponent, extreme) have traditionally used three methods for testing … (objects, subscriber’s, subjects’) perception in stimulus detection and difference detection experiments: method of limits, method of constant stimuli, and method of adjustment.

Wilhelm Wundt … (closed, invented, interfered) the method of limits. The subject reports whether he detects the … (stimulus, simultaneous, stamina). In ascending method of limits, some property of stimulus starts out at a level so low that the stimulus could not be … (defected, broken, detected), then this level is gradually increased until the … (participant, part, party) reports that he is aware of it. For example, if the experiment is testing the minimum amplitude of sound that can be detected, the sound begins too quietly to be … (looked at, perceived, touched), and is gradually made louder. In the descending method of limits, this is reversed. In each case, the threshold is considered to be the level of the stimulus property at which the stimulus is just detected.

In experiments, the ascending and … (descend, descending, descent) methods are used alternatively and the thresholds are averaged. A possible … (disadvantage, advantage, adventure) of these methods is that the subject may … (became, came, become) accustomed to reporting that he perceives a stimulus and may continue reporting the same way even beyond the threshold – the error of habitation. Conversely, the subject may also … (ants, activate, anticipate) that the stimulus is about to become detectable or undetectable and may make a premature judgement – the error of expectation.

To avoid these … (unpotential, potential, potentive) pitfalls, Georg von Bekesy introduced the staircase method in 1960 in his study of auditory perception. In this method, the sound starts out audible and gets quieter after each of the subject’s responses, until the subject does not report … (hearing, seeing, tasting) it. At that point, the sound is made louder at each step, until the subject reports hearing it, at this point the sound is made quieter in steps again. This way the … (exam, exercise, experimenter) is able to “zero in” on the threshold.

Instead of being presented in ascending or descending order, in the …(methodics, method, methodology) of constant stimuli the levels of a certain property of the stimulus are not related from one … (judge, court, trial) to the next, but presented randomly. This prevents the subject from being able to predict the level of the … (next, last, late) stimulus, and therefore reduces errors of … (habitable, habit, habituation) and expectation. The subject again reports whether he is … (can, must, able) to detect the stimulus.

The method of … (adjust, adjoin, adjustment) asks the subject to control the … (law, level, lawyer) of the stimulus, instructs him to alter it until it is just barely detectable against the background … (nose, noise, noisy) or is the same as the level of … (one, another, two) stimulus. This is also called the method of average error.

Task 16. Put proper words into the blanks in the texts:

a) Method of propellers. The method of propellers … (1) simultaneous comparisons of three stimuli, of which one at a time is taken as a target and the observer … (2) the size of the difference between the target and each of the other two stimuli. For example, an observer might be asked to compare chocolate, vanilla, and strawberry … (3). Beginning with chocolate as the … (4), he would judge the size of the difference between chocolate and vanilla, then the size of the difference between chocolate and strawberry, and report which difference was larger. Carrying out this procedure with a number of stimuli permits a rank-ordering of complex stimuli by an … (5) who would have said the task was impossible if asked to create a simple order. This … (6) is most effective for complex stimuli rather than simple size or brightness judgements.

Necessary words: observer, ice cream, involves, target, technique, judges.

b) Staircase procedure. Often the classic methods of experimentation are argued to be … (1). This is because, in advance of testing, the psychometric threshold is usually unknown and a lot of data has to be … (2) at points on the psychometric function that provides little information about its shape. Adaptive staircase procedures can be used in such a way that the points sampled … (3) around the psychometric threshold. However the cost of this efficiency, is that you do not get the same amount of information regarding the shape of the psychometric function as you can through … (4) methods. Despite of this, it is still possible to estimate the threshold and slope by fitting psychometric functions to the obtained data, although estimates of psychometric slope are likely to be more … (5) than those from the method of constant stimuli.

Staircases usually begin with a high intensity … (6), that is easy to detect. The intensity is then reduced until the observer makes a mistake, at this point the staircase reverses and intensity is increased until the observer … (7) correctly, triggering another reversal. The values for these reversals are then averaged. There are many different types of staircase, utilising many different decision and termination rules. Step-size, up/down rules and spread of the underlying psychometric function dictate where they converge on the psychometric function. Threshold values obtained from … (8) can fluctuate widely, so care must be taken in their design. Many different staircase algorithms have been modelled and some practical recommendations suggested by … (9).

Necessary words: staircases, inefficient, classical, are clustered, Garcia-Perez, collected, responds, variable, stimulus.

Task 17. Read the text “Gustav Fechner” and answer the questions:

Gustav Fechner

Gustav Fechner was born April 1, 1801. His father, a village pastor, died early in Gustav’s childhood, so he, with his mother and brother, went to live with their uncle. In 1817, at the age of 16, he went off to study medicine at the University of Leipzig. He received his MD degree in 1822.

But his interests moved to physics and math, so he made his living tutoring, translating and occasionally lecturing. After writing a significant paper on electricity in 1831, he was invited to become a professor of physics at Leipzig. There he became friends with a number of people, including Wilhelm Wundt, and his interests moved again, this time to psychology, especially vision.

In 1840 he had a nervous breakdown and had to resign his position due to severe depression. His interests switched again, now to philosophy.

Using the pseudonym Dr. Mises, he wrote a number of satires about the medicine and philosophy of his day. But he also used it to communicate, often in an amusing way, his spiritual perspective. As a panpsychist, he believed that all of the nature was alive and capable of awareness of one degree or another. Even the planet itself, he believed, had a soul.

He named the discipline psychophysics, which he defined as the study of the systematic relationships between physical events and mental events. In 1860 he topped his career by publishing the Elements of Psychophysics (from Коваленко 2000: 143-144).

Questions:

1) When was Gustav Fechner born?

2) Where and what did he study?

3) How old was Gustav when he received his MD degree?

4) How did he earn his living?

5) What were his interests in life?

6) What were his philosophical views?

7) What discipline did he give the name to?

8) What is psychophysics according to Gustav Fechner?

9) What is the title of his fundamental book?

Task 18. Rearrange the dates of G. Fechner’s biography in proper chronological order, starting with the earliest:

1) he published the Elements of Psychophysics; 2) G. Fechner was born; 3) he made friends with W. Wundt; 4) he named the science psychophysics; 5) he went to study medicine at the University of Leipzig; 6) he earned his living tutoring; 7) started to be interested in philosophy; 8) his father died; 9) his interests moved to physics and math; 10) severe depression; 11) Gustav’s family went to live at his uncle’s; 12) he used the pen-name Dr. Mises; 13) he received Doctor of Medicine degree; 14) he wrote an important work on electricity.