The Properties of the Organism

Effects that result from stimulus pairings seem to occur in almost all animal species. For example, classical conditioning has been demonstrated in worms, fruit flies (see https:// www . youtube . com / watch ? v= - dPfZE5adYg), snails, bees, fish, birds, rats, and people. Given the large

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differences between these species, it seems unlikely that, at the cognitive level, classical con-ditioning is always based on a single (cognitive or neuronal) mediating mechanism. It also highlights the need for caution when we generalize knowledge about conditioning in one animal species to another species. Even if there are major similarities between the moderators of classical conditioning in, for example, bees and humans (e.g., Bitterman, 1996), this does not mean that the same mental mechanism is responsible for conditioning in both animal species. The presence of classical conditioning effects in so many species is probably due to the fact that different animal species are confronted with similar problems in their world; the principle of convergent evolution holds that animal species evolve independently of each other but still display similar characteristics because of similarities in their interactions with the environment (Van Horik, Clayton, & Emery, 2012). Every animal has a greater chance of survival and reproduction if it can adapt to environmental regularities (e.g., if it can predict where food can be found or when dangerous situations will occur). Almost all animals will thus show classical conditioning when doing so increases their chances of survival and repro-duction. However, these similarities do not imply that the underlying mechanisms (at either the mental or neuronal levels) are always the same.

Moreover, there are also clear differences in the conditions under which classical condi-tioning occurs in different animal species. For example, research on the influence of intrinsic relations shows that one animal species can be more strongly influenced by certain regulari-ties than another animal species. For example, mammals will learn more quickly about rela-tions between the taste of food and nausea than about relarela-tions between the color of food and nausea (whereas there is no such difference in learning the taste- shock relation and the color- shock relation). Birds, on the other hand, seem to learn a relation between color and nausea more quickly than a relation between taste and nausea (whereas there is no such dif-ference in learning the taste- shock relation and color- shock relation). This could be due to the fact that the selection of food in mammals is determined mainly by the taste of the food, whereas in birds this is determined mainly by the visual characteristics of food. It also seems that certain instances of selectivity in learning are already present from birth, indicating a genetically determined influence on learning (e.g., Gemberling & Domjan, 1982).

In light of these differences, it is therefore useful to also view conditioning from the per-spective of the specific organism being studied (for an overview, see Domjan, 2005, and Bouton, 2016, pp. 193– 200). From this perspective, conditioning is primarily a function of the survival and reproduction of the organism. Conditioning (as an effect) is thus seen as an adaptive phenomenon that occurs in natural situations. This perspective has two impor-tant implications for how conditioning research will be carried out. If you want to learn more about conditioning in natural situations, then you need to take stimuli that can occur together in the natural environment of an organism. There is little point in using CSs that

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normally do not occur with USs in the environment of an organism (e.g., a light flash fol-lowed by an electric shock), as is the case in the majority of the existing conditioning experi-ments. Instead, it is better to use CSs that often occur together with the US in the organism’s environment, because they are potential causes of the US (e.g., food with a certain taste [CS]

and nausea [US]) or because the CS is an integral part of the US (e.g., the visual characteristics of a sexual partner [CS] preceding copulation with that partner [US]). Domjan (2005) calls such CSs ecologically valid.

Domjan (2005; Domjan, Cusato, & Krause, 2004) reviewed research that indicates that conditioning with ecologically valid CSs has different characteristics than conditioning with arbitrary CSs. He did research into sexual conditioning with quails (small birds that live pre-dominantly in grasslands, see figure 2.6). Domjan and his colleagues repeatedly showed male quails a fake (i.e., taxidermic) female quail (CS) just before they were given access to a real female quail and had sexual contact with it (US). As a result of these “pairings” (i.e., the joint presentation of the CS and the US), the number of times the males attempted to mate with the fake female (the CS) increased. Domjan (2005) also discusses aversion learning (see section

Figure 2.6 A Japanese quail.

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2.2.1.2) as an example of conditioning with ecologically valid CSs. One can say that there is a

“natural relation” between the taste of food and gastrointestinal sensations (including nausea).

A second consequence of an ecological perspective on classical conditioning is that extra attention is given to adaptive conditioning effects (i.e., conditioning effects that help the organism to survive and reproduce; also see note 5 in the introduction). An important adap-tive effect may be that the organism deals with the US in a more efficient way. The emphasis here is not on how conditioning as a procedure changes reactions to the CS (i.e., changes in the CR), but how conditioning influences reactions with respect to the US (i.e., changes in the UR). Domjan (2005) provides an overview of various findings that show that condi-tioning as a procedure can lead to changes in the UR. Perhaps the most imaginative is his own research into sexual conditioning in quails (see Domjan & Gutiérrez, 2019, for a recent review on sexual learning).

Again, Domjan showed a fake female quail to male quails (CS) just before they had access to a real female quail with which they could have sexual contact (US). During a subsequent test phase, the researchers evaluated not responses to the fake quail (CS) but rather actual sexual contact with the real female (US). They checked whether prior presentations of the CS had an effect on the efficiency of sexual contact and found that after the presentation of the fake quail (CS), sexual contact with the live quail was more efficient. For instance, the male needed less time to initiate sexual contact, semen contained more sperm, and the chance of conception of the egg was greater. These effects were obtained only when the fake quail was presented prior to the real female quail during the test phase (i.e., prior to sexual contact with a female) and when during a previous learning phase, the fake quail was paired with the presentation of a real female. The changes in the UR (the response to the sexually avail-able female) were therefore the result of prior pairing of the CS and the US. Another example is conditioned drug tolerance (see section 1.2.2). Stimuli (CSs) associated with the use of a drug (US) will reduce the response to the drug (UR) and thus reduce the likelihood of death by overdose. In sum, conditioning plays an important adaptive role in dealing with many important events.³