Good example of essay on the measurement of classical conditioning can be performed by employing a number

Various methods of studying classical conditioning

Classical conditioning is the simplest form of learning that occurs by developing a relation between the conditioned stimulus (CS) and unconditioned stimulus (UCS). It refers to a learning situation that can be traced to Ivan P. Pavlov’s (1849-1936) classical experiments. Classical conditioning is also called respondent conditioning or Pavlovian conditioning.
In classical conditioning, an unconditioned response (UR) is evoked by a preceding neutral stimuli (CS). The neutral conditioned stimulus begins to induce a response. It indicates the basic concept of classical conditioning and the response induced, after learning, by the conditioned stimulus is called Conditioned response (CR).

Eyeblink Conditioning: This is one of the commonly used methods to study classical conditioning. In this procedure, a puff of air blown towards an eye is used as US that induce UR in the form of eyeblink. There can be other URs also like the changing of heartbeat etc. This procedure is simple and has been used with cats, dogs etcetera (Gormezano, 1966). This method is convenient with the respondents.
Skin Conductance response (SCR): Electrical conductivity of the skin of a participant changes with the changes in the level of his emotionality. This procedure deals with change in frequency of skin conductance response (SCR). It is measured through electrodes, put in touch with the skin. This method along with the eyeblink method is being treated as best the methods to study the classical experiments of classical conditioning.
Evaluative conditioning: In this procedure, a neutral stimulus is presented with another stimulus that evokes evaluative affects in the subject. Both the stimuli are used in the form of words, pictures etcetera. For the measurement of UR and CR, evaluative conditioning depend on the evaluations of the participants depend. Evaluative conditioning does not use reflex-inducing UCs.
Conditioned Taste Aversion: In this procedure, a new taste of food or smell (flavour) is used as CS, followed by injecting an ill-inducing drug as US in the subject (for example, a rat). This procedure is mostly tested on rats and humans. The taste CS is represented to access of degree of conditioning after the subject (rat) recovers from illness. For example, it’s not uncommon for someone to associate the smell after consuming too much alcohol (even sight of the alcohol with the sickness that resulted from consuming the alcohol).
Face-slap eyeblink conditioning: it is similar to eyeblink conditioning but here a slap (or pretending a slap) is used as US. It evokes Ur in the form of eyeblink (or taking the head away from the path of the slap).
Appetitive conditioning: This procedure entails learning to predict something that satisfies a desire or appetite. Here a positive event is used as US (food delivery for Pavlov’s dog or sexually receptive female in Domjan’s case).
Classical conditioning depends on a number of factors that affect the degree to which it occurs. It involves the association of learning that takes place in the environment of an organism.

References

Holland PC. Conditioned stimulus as a determinant of the form of the Pavlovian conditioned response. J Exp Psychol Anim Behav Process 1977; 3: 77–104
Pavlov IP. Conditioned reflexes. Oxford, UK: Oxford University Press; 1927.
Wagner AR, Brandon SE. A componential theory of Pavlovian conditioning. In: Mowrer RR, Klein SB, editors. Handbook of contemporary learning theories. Hillsdale, NJ: Erlbaum; 2001. p. 23–64