ORIGINAL ARTICLE

Bodies and other visual objects: the dialectics of reachingtoward objects

Rob Ellis • Dan Swabey • John Bridgeman •

Benjamin May • Mike Tucker • Amanda Hyne

Received: 4 May 2011 / Accepted: 5 November 2011 / Published online: 19 November 2011

� Springer-Verlag 2011

Abstract Participants viewed video clips of a left or

right-handed reach toward an object that was orientated

with a handle to the left or right. They were required to

classify the object by making a left or right-handed key-

press and ignore the reach. These responses were, never-

the-less, affected by the observed reach in ways which

largely reflected the opportunities for complementary

actions in the viewed scenes, given the simultaneous con-

straints of the object orientation combined with the direc-

tion and hand of reach. These influences are claimed to

reflect the interdependency of the action possibilities that

arise from a set of objects and agents in three-dimensional

space that together determine behaviour.

Introduction

It is increasingly recognised that cognition should not be

regarded as a set of disembodied processes, but is strongly

determined by the constraints of its bodily implementation.

In the case of visual cognition, this embodied approach has

led to an emphasis on the role of vision in exploring the

world and, therefore, on the integration of vision and

action. It has been argued, for instance, that the action

properties of objects are an intrinsic part of its mental

representation. Evidence for this view includes a series of

studies employing a stimulus–response compatibility par-

adigm (Tucker & Ellis, 1998, 2001; Ellis & Tucker, 2000)

showing that the sight of an object potentiates (affords) the

actions associated with it. So for instance when participants

viewed an object to judge whether it was manufactured or

organic, their responses were facilitated when compatible

with an action needed to handle the object (a precision grip

for a pea or a power grip for a hammer are examples)

compared to the incompatible cases. Entirely analogous

object to action compatibility effects (which we term

micro-affordance) were observed for other elements of a

reach-to-grasp action: the hand of response and the direc-

tion of wrist rotation. The effects appear to be the results of

object-based attention, in that attending to a location on an

object does not necessarily elicit micro-affordance (Vainio,

Ellis, & Tucker, 2007) and an ignored object does not

produce action compatibility effects provided the target

object is cued by location (Ellis, Tucker, Symes, & Vainio,

2007). It seems that viewing an object, as an object,

potentiates the actions associated with it irrespective of

whether there is an intention in the viewer to act on it.

Similar action potentiation effects were observed when

participants classified named graspable objects (Tucker &

Ellis, 2004) or recalled previously seen objects (Derby-

shire, Ellis, & Tucker, 2006). It is concluded that micro-

affordance is a product of the representation of an object,

whether elicited by external or internal stimulation.

So-called canonical neurons (found in parietal-premotor

cortical circuits of monkey) respond both to an action and

to the visual properties of an object (Di Pellegrino, Fadiga,

Fogassi, Gallese, & Rizzolatti, 1992; Rizzolatti, Fadiga,

Fogassi, & Gallese, 1996). Generally, the action they code

and the objects they respond to are congruent, for instance

the grip type used to handle the object. It seems plausible

that the analogue of this system in humans is involved in

micro-affordance effects. In contrast to canonical neurons,

mirror neurons (also found in the parietal-premotor cortical

R. Ellis (&) � D. Swabey � J. Bridgeman � B. May �M. Tucker � A. Hyne

School of Psychology, University of Plymouth,

Drake Circus, Plymouth PL4 7AA, UK

e-mail: rellis@plymouth.ac.uk

123

Psychological Research (2013) 77:31–39

DOI 10.1007/s00426-011-0391-y

circuits of monkey) fire when actions are executed by the

individual, and upon observation of the same action exe-

cuted by another agent (Di Pellegrino et al., 1992; Gallese,

Fadiga, Fogassi, & Rizzolatti, 1996; Rizzolatti et al., 1996).

The existence of a human mirror system seems likely given

similar observation and execution activation effects infer-

red from transcranial magnetic simulation data (Hari et al.,

1998) and brain imaging (Gazzola & Keysers, 2009).

Actual measures of single cell responses in humans,

undergoing surgery to treat severe epilepsy, confirm the

existence of neurones responding to both the execution and

observation of particular grips (Mukamel, Ekstrom, Kap-

lan, Iacoboni, & Fried, 2010).

The human mirror system is thought to account for

behavioural imitation effects. For instance, Brass, Bek-

kering, Wohlschlager, and Prinz (2000) demonstrated that

observing an action (finger movements) facilitated a

response consisting of the same action even when the

observed action was an irrelevant stimulus property. Sim-

ilarly, Edwards, Humphreys, and Castiello (2003) showed

that observing prehension-facilitated compatible actions on

an object by the observer. Importantly for what follows,

there is evidence that the human mirror neurone system

includes responses that represent complementary actions.

In an fMRI study, participants observed an agent grasping

an object with either a precision or power grip, and then

prepared either an imitative or complementary response

(Newman-Norlund, van Schie, van Zuijlen, & Bekkering,

2007). Activation, as measured by the BOLD response,

was greater for the complementary cases.

Clearly, the properties of the mirror system suggest a

profound role for it in the coordination of intentional

behaviours among agents. It is commonly seen as under-

pinning our understanding of the actions and intentions of

others, allowing us to predict their behaviour and, there-

fore, successfully engage in joint actions with them (Riz-

zolatti & Craighero, 2004). A decision to cooperate or

compete with others might be expected to condition how

the mirror system influences our responses. Sebanz,

Knoblich, Prinz, and Wascher (2006) demonstrated affects

on event-related potentials that they argue show that indi-

viduals acting together form shared action representations.

Ocampo and Kritikos (2010) describe how instructions to

imitate or produce an action complementary to one

observed in a video, elicits imitative or complementary

effects, respectively, when participants are required, in

catch trials, to simply perform either a precision or power

grip (irrespective of the type of grip they observe in the

video).

Our concerns in this paper are somewhat different to any

of these preceding studies, having two key differences.

First, we aim to investigate the interaction of canonical and

mirror neurone systems, rather than examine their

independent influences on behaviour. For the most part,

they are considered to be different in kind, but we will

attempt to show that there is a case for regarding them as

different aspects of a common system for orchestrating the

actions of agents within their material culture. The second

difference, with the preceding studies, is that our proce-

dures are designed to assess the implicit effects on

responses of observed actions and the actions associated

with seen objects when both are irrelevant to the response.

In summary, we are interested in how the mirror neurone

system and the canonical neurone system interact when we

observe other agents acting on objects, irrespective of our

goals. So, for instance are micro-affordance effects mod-

ulated when another agent acts on a seen object? Does the

mere observation of another agent’s actions on an object

produce imitative or complementary action effects analo-

gous to the effects objects have on their observers? It is our

conjecture that mirror and canonical neural systems have

their primary role in coordinating the actions on objects by

agents. That is, they are part of a dynamic system in which

the actions of other agents and objects in a scene together

and simultaneously determine the actions afforded to an

observer. We presume that intentional mechanisms act to

harness or inhibit these afforded actions so that actual

behaviour is consistent with an agent’s current goals. To be

clear, we are interested in the implicit effects of other

agents and objects in combination.

So, the objects afford the actions associated with them in

human observers; actions performed by humans elicit those

same or complementary actions in other humans seeing

them. How are these two phenomena related? Some

behavioural studies have shown interactions between

affordance and imitation. Bach, Bayliss, and Tipper (2010)

showed that stimulus–response compatibility effects on

making a left or right responses in classifying the grip

aperture of a left or right moving arm were only significant

when the observed grip was congruent with an incidental

goal object. Vainio, Symes, Ellis, Tucker, and Ottoboni

(2008) had participants view an animation of a hand

making a power or precision grip, before classifying

objects compatible with a precision or power grip grasp, by

themselves making a precision or power grip. The usual

object by response compatibility effect was observed, but

only when the observed grip was congruent with the object.

Clearly, imitation and affordance effects may be mutually

constraining, and we now describe two experiments that

examine the effects of observing actual reaches towards a

goal object so as to better understand what we will call the

‘dialectical relations’ between agents and their material

culture.

When another person reaches toward an object our

attention will often be drawn to that object. Given we have

noticed both the action of the other agent and the object

32 Psychological Research (2013) 77:31–39

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they are reaching toward, how do the affordance and mirror

systems jointly affect our responses? In an initial study, our

participants were shown a video of a left or right-handed

reach, from the participant’s perspective, toward an object.

The hand movement was tracked and the object only came

into view towards the end of the observed reach. The task

of the participant was to classify the object using a right or

left-hand key-press. The object was orientated so as to be

optimally graspable with a left or right hand. Which of the

various action-related properties of these scenes affect

responses? Does the object orientation facilitate responses

with a congruent hand? Does the hand of reach depicted in

the video produce imitation effects? Or might comple-

mentary action effects be observed, such that observing a

reach toward the handle side of an object facilitates a

response with the hand that would be optimal for reaching

to the non-handle side?

Experiment 1

Method

Participants

All the 33 participants were students at the University of

Plymouth and they received course credit for participating.

All were right-handed by self-report and had normal or

corrected to normal vision. Informed consent was obtained

from each participant prior to commencing the task.

Apparatus and materials

Video clips were presented on a LCD screen approximately

50 cm distant from the participant. Stimulus presentation

was controlled by Eprime 2.0 and responses collected on an

Eprime button box.

The stimuli consisted of 112 clips of reaches toward

common objects. Each clip started with a view of a pair of

arms and hands resting on a table, viewed from above and

immediately behind (approximating therefore to the par-

ticipants’ perspective on the scene). One of the hands

reached forward in space, and the camera tracked this

movement. Each clip was edited such that the object first

came into view in frame number 82 of each clip (just over

3 s from the start), and each lasted a total of 5 s. The clip

ended with the hand located either at the handle or non-

handle side of the object, and before the shaping of the

hand for an actual grasp. There were 28 objects (named in

the Appendix) in the clips, half were kitchen implements

and half were tools. Each was filmed four times with all

combinations of left or right reaches to left- or right-ori-

entated objects. Figure 1 shows the start and end frame

from a typical case.

Procedure

After ten practice trials, there were 112 experimental ones.

Participants were told to response as quickly as possible

with a left-hand button press if they saw a kitchen object,

and a right-hand button press if they say a tool. There was a

Fig. 1 The start and end frames

of a video clip used in

experiment one (upper panels);

and in experiment two (lowerpanels)

Psychological Research (2013) 77:31–39 33

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blank screen for 500 ms between each trial, and at the end

of the video the screen displayed the final frame until the

participant responded or was timed out after 2 s.

Results

Response times

The response latency data were filtered for outliers, for

each participant, by removing responses plus or minus two

standard deviations from the mean. The remaining data

were analysed in a three-factor, within-subjects analysis of

variance, with object orientation, hand of reach of the

actor, and hand of response of the participant as the factors.

There was one significant main effect. Left-handed

responses were faster (M = 784 ms) than right-handed

(M = 798 ms), F(1,31) = 4.91, p = 0.034. This latter

difference, we assume, merely reflects the greater ease in

classifying a kitchen implement compared to a tool.

The theoretically important interaction of object orien-

tation by hand of response was significant, F(1,31) = 5.30,

p = 0.028, suggesting that object affordance was an

influence on responses. This took the form of a typical

object to object orientation compatibility effect; with

congruent cases, 12 ms faster than incongruent trials. Also

significant was the interaction of object orientation by hand

of reach of the actor, F(1,31) = 4.24, p = 0.048, sug-

gesting that the observed actions of the actor influenced

response too. Again, this took the form of a compatibility

effect; with congruent reaches, 18 ms faster than incon-

gruent trials. Critically, the actor reach effects are not

simply spatial, Simon-like, effects, as revealed by the

significant interaction of response by actor reach,

F(1,31) = 37.47, p \ 0.0005. In fact, responses were

39 ms slower whenever the hand of response and hand of

reach were the same.

There was a significant and striking three-way interac-

tion of object by reach and response, F(1,31) = 362.68,

p \ 0.0005, i.e. illustrated in Fig. 3. There appears to be

huge negative response to object orientation compatibility

effects whenever the actor reaches with their left hand

(congruent trials are 73 ms slower), and equally large

positive effects when they reach with their right hand

(congruent trials are 97 ms faster).

Error rates

Mean error counts were subject to a similar analysis. This

indicated main effects of object orientation (responses to

left-orientated objects were more accurate (M = 0.76) than

to right-orientated (M = 0.96), F(1,31) = 6.02, p = 0.020)

and the reach of the actor (responses on left reach trials were

more accurate (M = 0.71) than to right-orientated

(M = 1.01), F(1,31) = 18.20, p \ 0.0005).

The interaction of hand of response by object orientation

was significant, F(1,31) = 15.95, p \ 0.0005, but, unlike

the effect in reaction times, was a negative compatibility,

with congruent cases producing more errors (M = 1.06)

than incongruent ones (M = 0.67). The interaction of

object orientation by hand of reach of the actor was sig-

nificant, F(1,31) = 6.06, p = 0.020, and was also not

entirely consistent with the reaction time effect. That is,

although congruent reaches to left-orientated objects pro-

duced fewer errors than incongruent (M = 0.70 and 0.81,

respectively), the reverse was true for responses to right-

orientated objects (M = 1.20 and 0.72 for the congruent

and incongruent cases). The interaction of response by

actor reach was not significant, F(1,31) = 2.01,

p = 0.157), but, importantly, the trend was consistent with

the reaction time data, there being more errors when the

actor’s and participant’s reach was similar compared to

dissimilar (M = 0.95 and 0.78, respectively).

The three-way interaction of object by reach by response

is again significant, F(1,31) = 3.06, p = 0.003, but

appears to be driven by differential error rate for the

required responses for the two reaches. That is when a left

hand reach is viewed, more errors are made in the case of

what should be left-hand responses compared to the right-

hand response trials (M = 0.92 and 0.50, respectively),

suggesting that viewing a left-hand reach tends to elicit a

right-hand response in the participant. For right-hand reach

trials, there is little difference (the corresponding means

being 1.04 and 0.97). In both cases of reach, there is a

negative compatibility of hand of response by object ori-

entation, which contrasts, of course, with the reaction time

data. In the latter, a negative compatibility effect was found

for the left-hand reach trials and a positive compatibility

for the right-hand cases.

A summary of the error data can be inspected in

Table 1.

Table 1 Mean error scores in experiment one

Object

orientation

Reach of

actor

Response of

participant

Mean

error

Left Left Left 1.00

Right 0.40

Right Left 1.15

Right 0.47

Right Left Left 0.84

Right 0.59

Right Left 0.94

Right 1.47

34 Psychological Research (2013) 77:31–39

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Normalised reaction times

Given the various inconsistencies in the two data sets, a

further, similar analysis was conducted on a single data set

derived by dividing the reaction times by the proportion of

correct responses (Townsend & Ashby, 1978).

There were just two significant effects. The interaction

of hand of participant response by the observed hand of

reach, F(1,31) = 18.04, p \ 0.0005, confirms the perfor-

mance benefit for responding with the opposite hand

to that in the observed reach. The three-way interaction

of object compatibility by reach by response,

F(1,31) = 129.01, p \ 0.0005, also confirmed the effect

of the hand of the observed reach on the object compat-

ibility effect, with left-hand reaches associated with neg-

ative compatibility and right-hand reaches associated with

a typical positive compatibility effect. These interactions

in the normalised reaction time data are illustrated in

Fig. 2.

Discussion

To summarise this data set: (1) the reach of the actor did

produce overall effects on the responses, it being easier to

respond with the hand opposite to that of the observed

reach and (2) the actions associated with the object also

effected responses, but these were modulated by the

observed reach, with a negative compatibility effect when

observing a left-hand reach, compared to a positive com-

patibility effect when observing a right-hand reach. It is

worth reminding oneself that neither the reach of the actor

nor the action properties of the object are relevant to the

goal of the participants.

The influence on responses of the reach of the actor

was not a simple imitation or spatial congruency effect; it

could be interpreted as a complementary action effect.

That is, it was generally easier for the participants to

respond with the opposite hand to the observed reach,

suggesting the potentiation of a reach towards the part

that was not to be occupied by the end state of the actor’s

reach. The observation of an actor’s reach also strongly

affected the relationship between the participant’s

response and the orientation of the object, a reliable

negative compatibility effect being observed with left-

hand reaches and the reverse when a right-hand reached

was seen.

The modulation of the object to action compatibility

effect by the hand of reach could be regarded as a conse-

quence of the hand observed or the visual field in which the

hand reaches from, given the two are confounded. The next

experiment seeks to identify which is the case by simply

having the actor depicted reaching from a position opposite

to the participant.

Fig. 2 The interaction, in experiment 1, of the hand of response of

the participant and the hand of the actors reach (top figure) and the

three-way interaction of object orientation by hand of response by

actor’s reach (bottom two figures)

Psychological Research (2013) 77:31–39 35

123

Experiment 2

Method

Participants

All the 30 participants were students at the University of

Plymouth and they received course credit for participating.

All were right-handed by self-report and had normal or

corrected to normal vision. Informed consent was obtained

from each participant prior to commencing the task.

Apparatus, materials and procedure

These were identical to those in experiment one except the

video clips showed a reach from opposite the participant as

illustrated in Fig. 1.

Results

Response times

One participant’s data were excluded because of a high

error rate. The response latency data for the remainder

were filtered for outliers, for each participant, by removing

responses plus or minus two standard deviations from the

mean. The remaining data were analysed in a three-factor,

within-subjects analysis of variance, with object orienta-

tion,1 hand of reach of the actor, and hand of response of

the participant as the factors.

There were significant main effects of all three factors.

Consistent with the previous experiment, left-handed

responses were faster (M = 716 ms) than right-handed

(M = 828 ms), F(1,28) = 170.85, p \ 0.0005. This dif-

ference is an order of magnitude greater than that observed

in the first experiment however. Also in contrast to the first

experiment, there were main effects of object orientation

and the hand of the actor’s reach. Responses to left-ori-

entated objects were faster (M = 753 ms) than to right-

orientated (M = 791 ms), F(1,28) = 22.92, p \ 0.0005.

Responses to stimuli depicting a left-hand reach by the

actor were faster (M = 762 ms) than the responses to a

right-hand reach (M = 782), F(1,28) = 10.21, p = 0.003.

The interaction of object orientation by hand of response

was significant, F(1,28) = 21.60, p \ 0.0005, and is

broadly similar to that obtained, in non-normalised reaction

times, in the first experiment. Specifically, a left-hand

response to a left-orientated object is 81 ms faster than the

same response to a right-orientated object, whereas the

equivalent difference for the right-handed responses is only

39 ms. Given the main effect of hand of response, this

would suggest an influence of affordance on the right-hand

responses. The interaction of object orientation by reach of

the actor was significant, F(1,28) = 51.68, p \ 0.0005,

and rather more emphatic. It takes the form of a compati-

bility effect, but, given the actor’s perspective reverses the

handle orientation relative to the reach, it is best interpreted

as faster responses (M = 751 ms) whenever the actor’s

hand reached toward the non-handle side of the object

compared to a reach towards the handle (M = 793 ms).

The interaction of hand of response by hand of actor’s

reach was also significant, F(1,28) = 51.68, p \ 0.0005,

which reflects a huge advantage for responding with the

left hand (M = 666 ms) compared to the right

(M = 896 ms) when the actor reached with their right

hand, but little difference when the actor’s reach was with

their left hand.

Finally, the three-way interaction between the factors

was significant, F(1,28) = 11.65, p = 0.002. As in the first

experiment there was a striking difference between the

interactions of object orientation by hand of response for

the different reaches of the actor. There was no interaction

in the case of left-hand reaches, but a typical (positive)

compatibility effect whenever the actor reached with their

right hand.

Error rates

Mean error counts were subject to a similar analysis. There

was single, significant main effect of hand of response,

F(1,28) = 60.85, p \ 0.0005, consisting of more errors for

left-hand responses (M = 1.35) compared to the right hand

(M = 0.33). This is of course the reverse of the perfor-

mance benefit in the reaction time data for left-hand

responses.

Of the interactions, only the three-way object by

response and by reach was significant, F(1,28) = 10.37,

p = 0.003. This had the form of there being negative

compatibility of object orientation by hand of response for

observing left-hand reaches and a positive compatibility for

right-hand reaches.

A summary of the error data can be inspected in

Table 2.

Normalised reaction times

A similar ANOVA was conducted with normalised reac-

tion times to resolve the discrepancies between the two

performance measures and to provide a consistent com-

parison with the data from the first experiment.

There were significant main effects of object compati-

bility, F(1,28) = 16.28, p \ 0.0005, and the participant’s

hand of response, F(1,28) = 12.79, p = 0.001. Faster

1 That is the orientation relative to the participant, which is, of

course, reversed for the actor’s perspective.

36 Psychological Research (2013) 77:31–39

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responses were observed with left-orientated objects

(M = 802 ms) than those orientated to the right

(M = 843 ms); and left-hand responding was faster

(M = 797 ms) than right (M = 849 ms).

All three two-way interactions were significant, but the

three-way was not. Both the interaction of response hand

by object orientation, F(1,28) = 17.73, p \ 0.0005, and

the interaction of hand of actor’s reach by object orienta-

tion, F(1,28) = 30.09, p \ 0.0005, reflected similar, posi-

tive compatibility effects observed in the reaction time

data. The interaction of hand of response by actor’s reach,

F(1,28) = 202.28, p \ 0.0005, was rather more emphatic

than in the reaction time data alone; for both left and right

hand reaches, it was easier to respond with the opposite

hand. Given these reaches are seen from opposite the

participant it should be noted that a spatial compatibility is

associated with responses with opposing hands. These

interactions are illustrated in Fig. 3.

Discussion

Once again the participants’ responses were influenced by

the observed reach of the actor and the actions afforded by

the object, even though both were irrelevant to their task.

As in the first experiment, responding with the opposite

hand to that of the reach was easier than responding with

the same hand, but the effect was larger, with an average of

129 ms faster responses for the opposite hand, compared to

44 ms in the first experiment.2 One interpretation of this

contrast is that the change from an egocentric to an allo-

centric reach enhanced the complementary action effect

(Bruzzo, Borghi, & Chirlanda, 2008). It is equally plausi-

ble, however, that the difference has its origin in the

additional spatial compatibility that occurs in the second

Fig. 3 The interactions, in experiment 2, object compatibility by the

hand of response of the participant (top) and the depicted hand of

reach of the actor (middle); and the interaction of response by reach

(bottom)

Table 2 Mean error scores in experiment two

Object

orientation

Reach of

actor

Response of

participant

Mean

error

Left Left Left 1.69

Right 0.71

Right Left 1.93

Right 0.39

Right Left Left 1.90

Right 0.54

Right Left 1.44

Right 0.60

2 A difference confirmed by a significant three interaction of response

by reach by experiment, F(1,59) = 29.47, p \ 0.0005, in an

additional analysis.

Psychological Research (2013) 77:31–39 37

123

experiment, opposite hands sharing a left–right location in

the visual field.

The interaction of the reach of the actor and object

orientation is also open to an explanation in terms of

complementary action. That is, whenever the actor is seen

reaching toward the non-handle location on the object, the

participant’s performance was enhanced. On this interpre-

tation, a complementary action is conceived of as the

behavioural possibilities that are afforded jointly by an

object and the constraints that result from another agent

acting on that object.

General discussion

Participants observed another agent reaching to an object,

either from the observer’s point of view or an opposed

perspective. The orientation of the object was such that it

afforded either a left or right reach-to-grasp for the par-

ticipant. Despite the reach and the afforded actions being

entirely irrelevant to their task of classifying the object,

both influenced participants’ responses.

The influences of the observed reach were not simply

imitative as in previous studies (e.g. Brass et al., 2000).

When observing a reach, from either viewpoint, it was

easier to respond with the hand opposite to the reach. When

viewing a reach from opposite, participants found it easier

to respond when the reach was directed at the non-handle

side of the object. Whilst different in kind, both these

effects suggest responses tuned to the relations between an

object and another agent. In the first case, they seem

straightforwardly complementary action effects, in the

second they seem to reflect priority to another agent when

they reach toward the handle. It is important to note that

this facilitation of apparently complementary actions has

occurred in an experimental procedure which does not

direct manipulate participant’s expectations of the collab-

orative nature of the task as has been the case with previous

investigation of complementary action effects (e.g.

Ocampo & Kritikos, 2010). These new data provide a

demonstration of implicit, non-goal related influences of

the actions of other agents which are not merely imitative.

We assume that observing an act of grasping a single object

by another agent entails the (implicit) possibility of

the handing of that object to the observer. The recipient of

the object must necessarily prepare a grasp on a part of the

object not currently occupied by the other agent. Repeated

experience of such exchanges might be expected to adapt

the mirror neurone system, so it responds to complemen-

tary action, as a result of correlated sensorimotor learning

(akin to the mechanisms suggested for the formation of

imitative responses, as described by Gillmeister, Catmur,

Brass, and Heyes, 2008). We suggest that the handing of an

object between agents provides the foundations for more

elaborate and intentional forms of collaboration.

Object affordance effects, as reflected in object orienta-

tion to response compatibilities, were also found, but the

observed hand of reach modulated these. The relationship

was not, therefore, the equivalent of previous studies in

which the congruence between an observed action and an

object determined whether an object to response compati-

bility was obtained (Vainio et al. 2008; Bach et al. 2010).

Here we found that observing a left-hand reach, in both view

points, was associated with a negative object to response

compatibility and observing a right hand was associated with

the more usual positive compatibility.3 We think that this

unexpected and intriguing result may be best understood in

terms of the lateralisation in the brain of components of the

human mirror neurone system (MNS). Data from fMRI

studies of human participants engaged in cooperative tasks

(such as two individuals jointly maintaining the balance of a

virtual beam) indicate that joint activity appears to selec-

tively involve parts of the MNS in the right hemisphere

(Newman-Norlund, Bosga, Meulenbroek, & Bekkering,

2007, 2008). The implication that complementary actions

are lateralised in this way leads us to suggest that the

observation of a left-hand reach tends to elicit responses in

this system more directly or with greater potency than the

case when observing right-hand responses. It has to be

admitted, however, that this is highly speculative and, at this

point, inadequate as an account of the actual behavioural

differences reported here. But it does seem a fruitful starting

point for subsequent investigations.

Our major concern has been to demonstrate interactions

between elements of the motor system that occur when

agents jointly observe and act on objects. Using a simple,

but ecologically plausible, behavioural procedure, we have

shown that even the motor systems of mere observers,

irrespective of their goals, are simultaneously affected by

multiple sources of action possibilities. These influences

are claimed to reflect the interdependency of the action

possibilities that arise from a set of objects and agents in

three-dimensional space that together determine behaviour.

The actual behaviour is the outcome of dynamic and

sometimes conflicting influences from sources such as the

affordance associated with objects, the goals of the agents,

the spatial relations among the agents and objects, the

actions of the agents, and so forth. The actual behaviour of

an agent cannot of course itself be reduced to any of these

parts in particular, and it will also tend to have reciprocal

effects on those parts. Thus, to reach toward an object in a

crowded material and social world is best understood as a

dialectical process.

3 Albeit only in response latency in the case of the point of view

reaches.

38 Psychological Research (2013) 77:31–39

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Appendix

Objects used in the two experiments:

Kitchen implement Tool

Washing-up brush Adjustable spanner

Mug Large saw

Cheese grater Blue hacksaw

Kettle Chisel

Ladle File

Peeler Hammer

Pizza slicer Paintbrush

Spatula Pliers

Sieve Screwdriver

Spoon Spanner

Tin opener Wooden hacksaw

Whisk Wire cutters

Wooden spatula Torch

Wooden spoon Yellow hacksaw

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