Why it hurts: with freedom comes the biological need for pain

Abstract

We argue that pain is not needed to protect the body from damage unless the organism is able to make free choices in action selection. Then pain (including its affective and evaluative aspects) provides a necessary prioritising motivation to select actions expected to avoid it, whilst leaving the possibility of alternative actions to serve potentially higher priorities. Thus, on adaptive grounds, only organisms having free choice over action selection should experience pain. Free choice implies actions must be selected following appraisal of their effects, requiring a predictive model generating estimates of action outcomes. These features give organisms anticipatory behavioural autonomy (ABA), for which we propose a plausible system *

Trade-Offs between Avoidance of Noxious Electric Shock and Avoidance of Bright Light in Shore Crabs Are Consistent with Predictions of Pain

“…The finding that shocked crabs engage in alternative activities might account for the increased latency to enter the shelter and is consistent with the crabs apparently showing signs of anxiety when faced with a choice of remaining in the light or going into a dark shelter when the latter will produce a shock. Such shifts in behaviour were shown to improve survival from predatory fish in squid [ 28 ] and amphipods [ 29 ] and, thus, support the suggestion that pain must improve fitness beyond that achieved with nociceptive reflexes [ 1 , 23 ].…”

“…It shows that the response to the stimulus is flexible and enables the avoidance response to be more fitness-oriented than a reflex. A reflex should be the same regardless of other motivational requirements, whereas a decision that takes other motivational factors into account is a key predictor of pain because pain provides a better outcome in terms of fitness than a reflex [ 23 ].…”

Behavioural Indicators of Pain and Suffering in Arthropods and Might Pain Bite Back?

“…Finally, because high cognitive ability has been suggested to be required for a pain experience, examples within the arthropods will be briefly reviewed. This will be viewed in an evolutionary framework to help assess which arthropod groups might benefit from the emotional experience of pain [ 25 ]. The possible role of consciousness in pain experience is beyond the scope of the present paper and good references on this are available [ 9 ].…”

“…High cognitive ability enables large amounts of sensory information to be integrated, enables effective decisions [ 112 ], and provides flexibility in the responses to noxious stimuli that are guided by some expectation of outcome. Recently, the ability to choose between possible responses to noxious stimuli, rather than relying on an inbuilt algorithm, has been suggested to lead to the ability to feel pain [ 25 ].…”

“…These examples of gathering and integrating sources of information that enable effective decisions demonstrate that various taxa of arthropods have the behavioural flexibility that has been suggested as a requirement for pain to be of use [ 25 ]. These observations on cognitive abilities add to the evidence concerning the behavioural criteria for pain in crustaceans, insects, and, to a lesser extent, spiders.…”